EA for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest 1

Appendix A: Invasive plant descriptions

Invasive Plant Descriptions

Russian knapweed 

Acroptilon repens

Russian knapweed is a perennial shrub, forming dense colonies by adventitious shoots from 

widely-spreading black roots. Above-ground parts die back each winter; perennial roots send up 

new shoots in the spring. These roots can penetrate the ground to a depth of over 8 feet and can 

cover up to 12 square yards in two growing seasons. Stems are erect, openly branched, 18 to 26

inches tall. Pink to lavender flowers bloom from June to September (Whitson, 2002). It produces 

seeds sparingly, approximately 50 to 500 per shoot. Seeds are viable for two to three years in soil. 

Its primary method of reproduction is from vegetative propagation, with seed of secondary 

importance.

Russian knapweed reduces competition from other plants by allelopathy (production of 

biochemicals that inhibit the growth of other plants) (Beck, 2012). It also produces a neurotoxin 

that induces symptoms in horses identical to those of yellow starthistle when ingested (Knight,

2003). There is no effective treatment for either yellow starthistle or Russian knapweed poisoning 

because the affected areas in the brain undergo necrosis and do not regenerate.

Russian knapweed is a native to southern Ukraine, southeast Russia, Iran, Kazakhstan, and 

Mongolia; probably introduced into North America about 1898. It is now widely established 

throughout the west. It is a fairly common weed in the northern half of Arizona, and is also being 

documented in the southeastern part of the state (USDI, 2005). There are infestations along the 

Upper Verde River upstream from the Tonto NF. On the Tonto NF, very small populations have 

been documented in the vicinity of Gordon Canyon on Highway 260 (Horsley, 2005), and at

Shumway Millsite on the Payson Ranger District south of Payson (Fenner, 2005b).

Jointed goatgrass 

Aegilops cylindrica

Jointed goatgrass is a winter annual grass, 15 to 30 inches tall with one to many erect stems or 

tillers. The flower spike contains 2 to 12 spikelets, each with 1 to 3 viable seeds. Flowering and 

seed production occur May to July. Viability of seeds in the soil is 3 to 5 years; seeds retain 

75 percent of their viability after passing through a ruminant’s digestive tract (CDFA, 2005). 

Jointed goatgrass is native to southern Europe, but is now established in most winter wheat 

growing areas of North America. It was introduced from Turkey in the late 1800s (Colorado 

WMA, 2002). It is normally spread as a seed contaminant (Whitson, 2002).

Jointed goatgrass normally grows as a crop weed in parts of the U.S. where winter wheat is 

produced. CRISIS Weed Map and Data Server (2005), which compiles invasive plant records 

from California, Arizona, Nevada, New Mexico, Utah, Colorado, and parts of Idaho, Oregon, 

Wyoming, and Texas, shows no occurrences of jointed goatgrass in the west. Populations along 

Highway 87 from Payson to Strawberry, and in the Young area may be fairly recent, or at least 

have not been documented in any database to date.
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2 EA for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest

Tree of heaven

Ailanthus altissima

Ailanthus is a fast growing deciduous tree, a prolific seed producer, a persistent stump and root 

sprouter and an aggressive competitor with respect to the surrounding vegetation. It grows up to 

90 feet tall. (USFS, 2004, Feb.) It occurs primarily in disturbed areas, though it may invade 

undisturbed habitats, such as riparian areas. Seeds ripen in large crowded clusters from 

September to October and may persist on the tree through the following winter (Hu, 1979). An 

individual tree can produce 325,000 seeds per year which are easily wind-dispersed. Seeds are 

also dispersed by birds and water. Seeds are relatively short-lived (less than 3 years), and 

vegetative proliferation through root sprouting is by far the most common method of reproduction 

(Roye, 2003).

In the Americas, Ailanthus occurs from Canada to Argentina (Hoshovsky, 1988). The species was 

apparently introduced into America by two different routes. It was first introduced to America 

from China by way of England, by a Philadelphia gardener in 1784 (Hu, 1979). Because of its 

rapid growth and ability to grow in unfavorable conditions with little care, it became a common 

stock in eastern nurseries by 1840. The second route was through Chinese miners. During the 

days of the California gold rush, many Chinese miners brought Ailanthus seeds with them as they 

settled in California, probably because of its medicinal and cultural importance to them.

The production of toxic chemicals by Ailanthus may also explain the success of this plant. An 

aqueous extract of Ailanthus leaves has been shown to be toxic to 35 species of gymnosperms and 

10 species of angiosperms (Mergen, 1959). This may be important in limiting natural succession 

in Ailanthus stands.

A recent clinical observation recorded in the Annals of Internal Medicine documents a case of 

myocarditis that was traced to the patient having worked as a tree surgeon on a team responsible 

for clearing heavy infestations of tree of heaven. Symptoms included abdominal pain, chest 

pressure that radiated to both arms, and shortness of breath. The patient reported that all of his 

coworkers also exhibited these same symptoms. Among its many uses in folk medicine, sap of 

the tree of heaven is thought to be a cardiac depressant and has been used to slow heart rate 

(Bisognano, et. al., 2005). 

In Arizona, this tree is mostly associated with mining towns. It has been documented around 

Cottonwood, Camp Verde, and Jerome. There are recent records (1999 and 2002) from Santa 

Cruz and Pima counties on the Coronado National Forest (CRISIS, 2005). On the Tonto NF, it 

has been documented on the Verde River near Childs, in the towns of Superior and Globe and on 

National Forest lands nearby. In the spring of 2005, a few pole-sized plants were documented 

near the confluence of Pinal Creek and the Salt River (Fenner, 2005a). Seed were probably 

carried down the creek from the town of Globe, where the tree grows in abundance. It has been 

documented growing in the town of Payson near the Forest boundary. It was recently found 

growing vigorously in Columbine Canyon on the Cave Creek Ranger District. It has sprouted 

prolifically since the Cave Creek Complex Fire of 2005, and probably occupies approximately 

one acre. The original tree was most likely planted by Camp Creek recreational residence 

homeowners.
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EA for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest 3

Camelthorn 

Alhagi maurorum

Camelthorn, a spiny, intricately branched perennial shrub, grows to a height of 11⁄2 to 4 feet. The 

greenish stems have slender spines 1⁄4 to 13⁄4 inches long. Single leaves are wedge-shaped and 

alternate. Flowers are small, pea-like, pinkish purple to maroon, occurring on short spine-tipped 

branches on the upper portion of the plant. The entire plant dies back to the ground every winter 

and resprouts from its extensive root system the following spring. It can grow through pavement, 

and the thorns can flatten car tires. Where it grows near highways, it causes extensive cracking in 

the asphalt, and constant road repairs are necessary (Horsley, 2004).

Camelthorn, a member of the pea family, was introduced from Asia and grows well on dry or 

moist sites. It spreads rapidly along streams and canals (Colo. WMA, 2005)

It is considered one of the most difficult noxious weeds to eradicate, due to its extensive root 

system. It is an aggressive perennial that sends thick rhizomes out 12 meters or more from the 

parent plant. Seeds may be viable for years, although reproduction is mostly vegetative; seedlings 

are rarely found (DiTomaso, 2003a). Although the plant is very thorny, it is apparently also very 

palatable. Passage through ruminants’ digestive tracts serves to scarify the extremely hard seed 

coats, thus increasing germinability (CDFA, 2005).

In Arizona, camelthorn has been documented growing between 100 and 5,000 feet in elevation 

(ADOT, 2005). It has established heavy infestations in the northeastern part of the state. It grows 

along ditches and canals in the vicinity of Painted Rock Dam, southwest of Phoenix, and has 

recently been found in fields on the west side of Phoenix near Loop 101 near an alfalfa field 

(Northam, 2005). Arizona Department of Transportation has been applying herbicides to an 

infestation in Chandler for some years. They have also worked for several years on a small 

infestation along Highway 60 a few miles north of Globe (Horsley, 2005). Other camelthorn 

infestations farther north along Highway 60, north of the Salt River, are also very close to the 

Tonto NF; there could easily be camelthorn growing along the Upper Salt River that have spread 

from these infestations. Surveys of the Upper Salt River during the spring of 2005 did not find 

camelthorn from Cibecue Canyon to the take-out point above the Diversion Dam. The first seven 

miles below the Highway 60 bridge were not surveyed (Fenner, 2005a).

Giant reed 

Arundo donax

Giant reed, also known as wild cane, is a tall, perennial grass that can grow to over 20 feet in 

height. Its fleshy, creeping rootstocks form compact masses from which tough, fibrous roots 

emerge that penetrate deeply into the soil. Leaves are elongate, 1 to 2 inches wide and a foot long. 

The flowers are borne in 2-foot long, dense, plume-like panicles from August through October.

Reproduction of giant reed is primarily vegetative, through rhizomes, which root and sprout 

readily. Little is known about the importance of sexual reproduction in giant reed, or about its 

seed viability, dormancy, germination, and seedling establishment (Benton, et. al., 2005). It does 

not produce viable seeds even in most areas where it appears to be well-adapted (Perdue, 1958). 

Giant reed becomes established in moist places such as ditches, streams, and riverbanks, growing 

best in well drained soils where abundant moisture is available. It tolerates a wide variety of 
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4 EA for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest

conditions, including high salinity, and can flourish in many soil types from heavy clays to loose 

sands.

Giant reed is widely dispersed into all of the subtropical and warm temperate areas of the world, 

mostly through intentional human introductions. It was probably first introduced into the United 

States at Los Angeles, California in the early 1800s. Today, giant reed is widely planted 

throughout the warmer areas of the United States as an ornamental and in the Southwest, where it 

is used along ditches for erosion control (Benton, et al., 2005).

Arundo chokes stream channels, crowds out native plants, interferes with flood control, and 

increases fire potential. The long, fibrous, interconnecting root mats of giant reed form a 

framework for debris dams behind bridges, culverts, and other structures, which leads to damage. 

It ignites easily and can create intense fires. It can float miles downstream where root and stem 

fragments may take root and initiate new infestations. Due to its rapid growth rate and vegetative 

reproduction, it is able to quickly invade new areas and form pure stands at the expense of other 

species. Once established, giant reed has the ability to out-compete and completely suppress 

native vegetation (Hoshovsky, 1986).

This species has been planted in many rural communities throughout the state. It grows near the 

headwaters of the Verde River at Dead Horse State Park, near the Irving Power Plant on Fossil 

Creek, and is common in the towns of Camp Verde, Globe and Superior. It can be difficult to 

distinguish from common reed (Phragmites australis), which grows on every continent except 

Antarctica, and is probably the most widespread flowering plant in the world (Tucker, 1990).

Because Phragmites has invaded and formed near-monotypic stands in some North American 

wetlands, only in recent decades there has been some debate as to whether or not it is indigenous 

to this continent. Convincing evidence that it grew in the western U.S. long before European 

contact is now available. Archaeological reports document preserved Phragmites remains in the 

southwestern U.S. dating back 40,000 years (Saltonstall, 2005).

Phragmites grows along the Verde River, and has increased in density during the recent drought 

(Fenner, 2003). Arundo has been identified at several sites along the Verde River, growing in 

association with Phragmites. Arundo is capable of also growing on xeric sites outside of the 

floodplain, while Phragmites is not. If a large river flow were to scour the river channel and 

floodplains, they could be opened up to replacement of Phragmites by Arundo.

Onionweed 

Asphodelus fistulosus

Onionweed is an herbaceous perennial in the lily family (Liliaceae). It grows to about a foot tall 

and almost as wide. Clusters of long, tapering, round, hollow leaves very much resemble chives 

or scallions. Leaves sprout after winter rains, with flowers appearing in spring. Plants die to the 

ground during dry seasons. Fruits are 1/8-inch round capsules. 

Onionweed might be confused with some native onions (Allium spp.). Allium macropetalum

(desert onion) is a much shorter plant with leaves rarely more than four inches tall. Taller native 

onions grow in different habitats than onionweed. Onionweed is known to grow in very dry sites 

where native onions would not grow.
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EA for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest 5

Onionweed is an aggressive invasive species. Introduced as an ornamental, it easily escapes 

cultivation into surrounding un-irrigated land. It seeds prolifically (2 to 13,000 seeds per plant 

annually) and can establish large populations quickly (Fox, 2004). Seeds remain viable in the soil 

for many years. Onionweed is unpalatable to cattle and apparently to most wildlife, so it is very 

persistent once established. To date it tends to invade disturbed ground, so it is unclear if it will 

be a threat to natural communities.

This plant is native to southern Europe, Mediterranean Africa, and western Asia. In the United 

States onionweed occurs in California (in several coastal southern counties), Arizona, New 

Mexico, and Texas. Onionweed is also known to be in Mexico. Plants introduced into the United 

States in the 1980s may be the progenitors of the Arizona population. They were offered for sale 

in Alpine, Texas and Phoenix, Arizona as early as 1984. Some of the original U.S. plants were 

collected from a naturalized population near Saltillo, Coahuila, Mexico, where the species was 

documented in 1930 (Arizona-Sonora Desert Museum, 2005).

Some nurseries offer onionweed as an ornamental, even though it is a prohibited noxious weed in 

many states as well as a federally-listed noxious weed. Plants have been found in Arizona from 

about 2,000 feet elevation to at least 4,500 feet (Arizona-Sonora Desert Museum, 2005). Arizona 

infestations are primarily in the southeastern corner of the state, in areas above the desert that 

receive moderate winter rainfall. A few small infestations have been found in Tucson. An 

infestation was discovered in Ajo in 1989 by an Arizona Department of Agriculture employee, 

who eradicated it by hand pulling all of the plants. In 1994, it was discovered in a demonstration 

plot at a botanical garden in Tucson. That infestation was also eradicated by hand removal. It has 

been discovered in several sites in Tucson and southeastern Arizona, including the Audubon 

Research Ranch, plant nurseries, and residential yards. The most recently identified infestations 

are near Tombstone, Arizona along Highway 80 (Northam, 2005) and in Sedona (Moser, 2005).

A well-established population in suburban Tucson was reduced to only two plants after the severe 

drought of 2002. Germination and plant establishment seem to be enhanced by fire, as observed 

after fires burned over an infestation near Elgin in 2002 and 2003 (Northam, 2005). Onionweed 

has not been documented on the Tonto NF.

Wild oats 

Avena fatua

Wild oats is a cool season, annual grass that originated in the Mediterranean area, and has 

naturalized throughout the world everywhere cereal grains are grown. Besides being an 

agricultural weed, it has become a common weed of roadsides and undisturbed wildlands in the 

western U.S. It was well established in California by the late 1700s.

It is a tall grass, growing up to 4 feet tall, but usually 2 to 3 feet tall. Fields of wild oats can 

produce up to 10,000 seeds per square meter (Brusati, 2004). Seeds can survive 4 to 7 years, but 

99 percent of seeds germinate before 4 years. Seedbank half-life is estimated to be 6 months 

(Murrumbidgee Catchment Authority, 2010). 

It has been used in Arizona to revegetate disturbed areas near highways, and has spread into lowelevation vegetation types from juniper grassland to the Sonoran Desert. It is found along most 

highways on the Tonto NF. It dries out by late spring, providing a source of dry standing fuel to 

carry desert fires from the highway into adjacent uplands. 
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6 EA for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest

Black mustard 

Brassica nigra

Black mustard is an annual cool-season forb that grows 2 to 8 feet tall. Stems are erect, with some 

dense hairs on lower portions, and upper stems usually smooth. Leaves vary from 2 to 10 inches 

long, and 1 to 6 inches wide. Leaves are stalked and deeply lobed. Flowers are larger and brighter 

yellow than those of Asian mustard. This species can be easily differentiated from wild and Asian 

mustard in that its seed pods are closely appressed to the stem at maturity (Whitson, 2003).

Mustard seed can remain viable in the soil for over five years.

This plant has been reported to have an allelopathic substance in its leaves (Munir, et al., 2002).

While it tends to grow in clumps that crowd out native plants, it has been considered to have a 

low invasive potential by other states in the West.

Black mustard was introduced to the U.S. from the Mediterranean area, possibly as a seed grain 

contaminant. It now grows in nearly every state (Ewing, 1999). It is increasing in abundance in 

Arizona. On the Tonto NF it has been identified growing along Highway 188 through Tonto 

Basin, and in revegetation sites along Highway 87and in the Cave Creek Complex Fire area. It 

was apparently also a contaminant in seed used for revegetation of safety zones created during 

suppression of the Willow Fire in 2004; because inspections in 2005 found black mustard plants 

in nearly every safety zone that was seeded. An infestation covering many acres has developed 

over the last several years on the Agua Fria National Monument, starting at I-17 and extending 

along the mesa tops to the Agua Fria River.

Asian mustard 

Brassica tournefortii

This cool-season annual forb germinates in the late fall to winter, and grows very rapidly, seeding 

out as early as February of the following year. One mature plant can produce as many as 9,000 

seeds. Seed longevity is unknown, but based upon observations of other Brassica species, is 

probably several years (Sanders & Minnich, undated).

Asian mustard replaces other native and invasive species by growing in high densities, using soil 

nutrients and moisture before other plants. It often causes native annuals to die early in the spring, 

due to lack of available soil moisture (Brooks, 2003). It may have an adverse effect on desert 

tortoise by reducing biomass of native annual forbs and grasses that have palatable leaves and 

stems close to the ground at the time of year when tortoises are coming out of their dormant 

period and foraging for food (Brooks, 2003).

Asian mustard is native to the deserts of North Africa, the Middle East, and Mediterranean lands 

of southern Europe. It was probably introduced to this country with date palms brought from the 

Middle East in the early 20th century to Coachella Valley. It experienced population explosions

during above-normal winter/spring precipitation years of 1977 to 1983 (Sanders & Minnich,

undated) and again in 2004.

Asian mustard may have been classified as a “B” species prior to the winter/spring of 2004 to 

2005. Higher than normal precipitation following years of drought that had removed ground 

cover at lower elevations, resulted in the 2004 population explosion of Asian mustard. After that

wet winter/spring, Asian mustard quickly proliferated to occupy roadside and field disturbed 
Appendix A

EA for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest 7

areas from southern Arizona to Kingman and the Arizona Strip, into western New Mexico and the 

deserts of eastern California. It had been present in low numbers before 2004, but seemed to take 

advantage of abundant cool season precipitation to extend its range dramatically. Mature plants 

break off and tumble, scattering seed from pods. Asian mustard plants have moved from the 

right-of-way along Highway 87 to distances of a quarter mile or more into undisturbed desert, 

where tumbling plants have hung up under mesquite, palo verde and catclaw, or along minor 

drainages (Fenner, 2005b). A Plant Assessment Form for this species, completed by the 

California Exotic Pest Plant Council reports that it has spread rapidly from the Sonoran Desert to 

the Mojave Desert during the 1980s and 1990s (Brooks, 2003).

It is now widespread through the Tonto NF, from Cave Creek Road, to the lower Salt River, 

Highway 60, Highway 87 to Sunflower, Highway 188 (mostly near new construction at the south 

end) and roads and drainages through the Mesa, Globe, and Tonto Basin ranger districts.

This species appears to progress in waves, after extremely wet years. It may not be a dominant 

weed in years following the wet winter of 2004 to 2005, but its seed is now in the soil on many 

acres of National Forest, waiting for another wet winter.

In addition to replacing native annual species, Asian mustard matures very early in the spring, 

leaving a thoroughly dried, often large quantity of biomass along roadsides that can easily carry 

fire into the desert. Its spreading panicle and growth habit of leafless stems with a rosette of large 

leaves at the base may prevent it from carrying fire on its own, unless it is growing on a steep 

slope. But presence of dried annual grasses can serve to carry the fire, which is fueled by Asian 

mustard, for long distances.

Red brome, rescuegrass, downy brome, Japanese brome, ripgut brome 

Bromus rubens, B. catharticus, B. tectorum, B. japonicus, B. diandrus

Red brome is native to Europe. It was introduced to the U.S. in the 1800s. By 1870 it had 

overtaken California’s overgrazed rangelands. Its range in the west is similar to that of downy 

brome (cheatgrass), except downy brome grows at higher elevations, as it is better able to 

withstand frost (Newman, 2004). Temperatures below freezing kill red brome. Downy brome is 

native to Eurasia and the Mediterranean area. It was brought to this country and had extensively 

invaded the Great Basin and other parts of the west by the late 1800s (Carpenter and Murray,

1999). Japanese brome was brought into the U.S. from Europe. It was intentionally planted in 

some areas in the Midwest, for rangeland improvement. Unlike other bromes, it is not adapted to 

survive frequent fires, but prefers a layer of litter for maximum germination.. Rescuegrass was 

introduced to the U.S. from South America. It is cultivated as winter forage in southern states. It 

is an annual or short-lived perennial cool-season grower. Originating in the Mediterranean area, 

ripgut brome was first reported in the San Francisco area by Watson (1880). It became widely 

established throughout California before the end of the 19th century (Parish, 1920).

These cool-season annual grasses are all classified as “C” species on the Tonto National Forest.

This means they are so abundant and widespread that eradication is not a realistic goal. They are 

included in this analysis for treatment, so that they can be removed from strategic sites. Brome

grasses created a continuous fuel source that carried desert fires to engulf unprecedented acreages 

in the summer of 2005. Seven years of drought, followed by an exceptionally wet winter and 

spring created a landscape where native perennials had died and been replaced by lush annual 

growth for a few months during the spring months. When early lightning struck in the desert, it 
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8 EA for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest

ignited the continuous groundcover of red brome that carried fast-moving fires that could not be 

contained for weeks (Fenner, 2005b). The Cave Creek Complex Fire, second largest fire in the 

state, and the largest ever to burn in the Arizona desert, was fueled by red brome. Nearly 250,000 

acres burned – 20 percent of which were classified Sonoran Desert scrub. A significant part of the 

cactus/succulent component of the vegetation was killed. Deserts did not evolve to withstand fire 

– their normal community structure is widely-spaced plants with cryptogamic soils between the 

plants.

Downy and Japanese bromes grow at higher elevations. The fire hazard they create is not as 

significant an effect to the vegetative types in which they grow, which are typically adapted to 

fire frequencies of 5 to 7 years. However, they move into forests and rangelands where grazing or 

other disturbance has reduced the competitiveness of native grasses, and replace them, thus 

changing perennial grasslands to annual grasslands. In a dense stand, the extensive, fibrous root 

system can extract all the available moisture from the upper soil profile, so there is none available 

for slower growing native species.

Downy brome, or cheatgrass seedlings germinate with fall precipitation. Roots can grow 

throughout most of the winter at soil temperatures as low as 37°F, and can reach a maximum 

depth of 3 to 4 feet as plants mature. Under ideal conditions, a dense infestation of downy brome 

can produce over 500 pounds of seed per acre (1 pound of seed contains approximately 250,000 

seeds). Dry matter production of downy brome on rangeland sites can vary from less than 100 

lb./acre on the poorest sites to more than 2,000 lb./acre on the better sites. The brome is of little 

forage value because it dries quickly, leaving dried awns that can create serious sores in mouths 

of livestock.

Rescuegrass grows from 140 to 7,000 feet elevation. It is reported to compete with and displace 

native plants, especially on riparian sites (Marshall, et al., 2000 & Northam, 2009).

Ripgut brome grows early, creating a continuous fine fuel as do other bromes, but does not tend 

to grow in monotypic stands as other bromes do. It is a prolific seed producer (over 1,000 

seeds/square foot), but seeds have a short soil viability (under 3 years). Infestations typically start 

in disturbed areas, but can move into openings in wildlands. Florets have sharp awns and can 

wedge into clothing, fur, and machinery. It can also spread as a contaminant in grain seed (Kyser,

2004). Ripgut brome plants germinate, grow and produce seeds during the winter, spring and 

early summer. Seed production can range from 600 to over 3,000 per plant.

Bromus species are contaminants of grain and wool, damage animal hides and host a range of 

serious cereal diseases. In pastures the seeds penetrate eyes, mouths, and feet of grazing animals.

Rescuegrass has been identified growing in Yavapai County at Montezuma Castle National 

Monument, not far from the Tonto NF’s western boundary (Guertin, 2003). It probably grows on 

the Tonto NF as well. Both ripgut brome and rescuegrass grow in the Tucson Mountains in 

southern Arizona (Rondeau, et al., 2000). Ripgut brome has been identified growing on these 

National Monuments that neighbor the Tonto NF: Tuzigoot, Montezuma Castle, and Tonto 

National Monuments (Guertin, 2003), and at the Hassayampa River Preserve (Drezner, et al.,

2001). It has also been identified on the Verde River where Highway 260 crosses, near the town 

of Strawberry, in the area of the Willow Fire of 2004 west of Rye, and at Sycamore Creek along 

the Beeline Highway (Northam, 2005). It grows in riparian areas from below 2,000 feet up to 

about 5,000 feet on the Tonto NF (Northam, 2005). 
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EA for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest 9

Globe-podded hoary cress, hairy white-top 

Cardaria draba, C. pubescens

Whitetop is a deep-rooted perennial in the mustard family, native to Russia. It was first brought to 

the U.S. in the late 1800s. It often grows up to 2 feet tall, with roots going 12 to 30 feet deep. It 

can produce 50 shoots in a square yard. With no competition, one plant can spread to cover an 

area 12 feet in diameter in its first year. It reproduces by seed and by root segments. An extensive 

root system is established early in the life of a seedling – a 25-day old plant can have a taproot 

10 inches deep, with 5 to 6 lateral roots with vegetative buds. One plant can produce up to 4,800 

seeds at maturity. The seeds are relatively short-lived, retaining viability for only up to 3 years in 

the soil (CNAP, 2000).

This plant is found on alkaline, disturbed soils and is highly competitive once it becomes 

established (Whitson, 2002).

Hoary cress may be at least mildly toxic to livestock. The plant contains glucosinolates, which are 

sulfur-containing compounds that can form toxic compounds in the digestive tracts of animals. 

These compounds are generally present at low levels, which are normally tolerated by livestock 

and wildlife. While hoary cress has some forage value, managers should use caution when 

allowing animals to graze hoary cress-infested rangelands (McInnis, et al., 1993).

Populations have been recorded in Prescott, Camp Verde, Flagstaff, and Cottonwood, and on the 

upper Verde River near Perkinsville (USFS, 2004, Feb.; Northam, 2005). It has been documented 

on the Tonto NF, growing on the Pleasant Valley Ranger District (SWEPIC, 2005; Northam,

2005).

Plumeless thistle 

Carduus acanthoides

Members of the genus Carduus are native to Europe and Asia. Plumeless thistle is an erect 4 to 5 

foot tall purple-flowered biennial. Leaves are pinnately-lobed and slightly hairy, extending down 

the stem to form spiny wings. Flowering is induced by a cold period, thus it may not be adapted 

to invading lower elevations on the Tonto NF. First flower heads produce up to 1,500 seeds, with 

later flower heads producing only about 25. About 99 percent of seeds fall within 150 feet of the 

adult plant, and are viable for a short time. A study of plumeless thistle suggested that viable 

seeds of this species rarely persist in the soil seedbank due to decomposition and seed predation 

by insects, mammals, and birds (CDFA, 2005). Competition by perennial grasses suppresses 

growth of this thistle.

This species has not been documented on the Tonto NF. The closest population to the Tonto NF

is at the Petrified Forest National Park 

Musk thistle 

Carduus nutans

Musk thistle is an aggressive, biennial herb with showy red-purple flowers and spiny stems and 

leaves. Mature plants range in height from 11⁄2 to 6 feet tall, and have multi-branched stems.

Leaves are dark green, coarsely lobed, with a smooth waxy surface and a yellowish to white spine 
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10 EA for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest

at the tip. The large disk-shaped flower heads, containing hundreds of tiny individual flowers, are 

11⁄2 to 31⁄2 inches in length and occur at the tips of stems. Flower heads will droop to a 90-degree 

angle from the stem when mature, hence its alternate name, nodding thistle. The number of 

seedheads per plant is site-dependent and ranges from about 24 to 56 on favorable sites and 1 to 

18 on less favorable sites. Flowers emerge in early May to August and seed dissemination occurs 

approximately one month after the flowers form. A single flower head may produce 1,200 seeds 

and a single plant up to 120,000 seeds, which may be wind-blown for miles. Seed may remain 

viable in the soil for over ten years, making it a difficult plant to control.

It is unpalatable to wildlife or livestock, and establishes easily in areas opened up by disturbance, 

such as fire or overgrazed rangelands (Remaley, 2005b). In piñyon-juniper communities, 

cheatgrass and musk thistle (among other invasive plants) tend to establish and dominate, 

replacing native grasses and forbs, following fires (Zouhar, 2002). When musk thistle plants bolt, 

older rosette leaves begin to decompose, releasing allelopathic chemicals into the surrounding 

soil (Duncan, 2005).

Musk thistle is a native of eastern Europe, and was introduced to the eastern U.S. in the mid1800s (Duncan, 2005). It is now found in nearly every state, from sea level to 8,000 feet 

elevation. Musk thistle is very common in the Four Corners area (SWEPIC, 2005), and has been 

documented at several locations on the Coconino and Kaibab national forests in northern Arizona 

(USFS, 2004, Feb.). The species has not been documented on the Tonto NF.

Southern & Field sandbur 

Cenchrus echinatus, C. spinifex

Southern sandbur, although a native grass, is on the Arizona prohibited and regulated weed lists. 

Both species are summer annuals that aggressively colonize open disturbed sites such as 

roadsides and ditch banks. They compete poorly with dense vegetation and rarely become 

established where there is a good ground cover of native species (CDFA, 2005).

Spikelets are enclosed by fused spiny bracts that form a bur. Burs disperse by clinging to skin and 

fur of animals, shoes and clothing of humans, vehicles, and by floating on water. Seed from upper 

spikelets normally germinate within one year; those from lower spikelets may remain dormant for 

up to five years. One plant can produce up to 1,000 seeds (SWEPIC, 2005).

Bur spines are stiff and can injure the mouths of grazing animals.

Sandbur grows along the right-of-way of Highway 60 east of the Tonto National Forest, on the 

Fort Apache Reservation. It has also been identified on the Tonto NF, on the right-of-way of 

Highway 188 a few miles north of Globe, and within the town of Globe.

Spotted knapweed 

Centaurea biebersteinii

Spotted knapweed is a biennial or short-lived perennial. Its name is derived from the spots formed 

by black margins on the flower bract tips. Spotted knapweed typically forms a basal rosette of 

leaves in its first year and flowers in subsequent years. Rosette leaves are approximately 8 inches 

long by 2 inches wide, borne on short stalks, and deeply lobed once or twice on both sides of the 
Appendix A

EA for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest 11

center vein, with lobes oblong and wider toward the tip. The taproot is stout and deep. Flowers 

are purple to pink, rarely white, with 25 to 35 flowers per head. Plants bloom from June to 

October, and flower heads usually remain on the plant (Carpinelli, 2005).

It is native to Central Europe, east to central Russia, and western Siberia. Spotted knapweed was 

introduced to North America from Eurasia as a contaminant in alfalfa and possibly clover seed, 

and through discarded soil used as ship ballast. It was first recorded in Victoria, British Columbia 

in 1883 and spread further in domestic alfalfa seeds and hay, before it was recognized as a serious 

problem. Today it is widely distributed in Canada and nearly every state in the U.S. 

Spotted knapweed plants in North America generally live 3 to 7 years, but can live nine years or 

longer. Plants can sprout from buds on the root crown. Reproduction is by seed only, and plants 

are capable of producing 500 to 4,000 seeds per square foot per year. About 90 percent of the 

seeds are viable at the time of dispersal, and they can remain viable in the soil for 5 to 8 years. 

Most seeds are dispersed near the parent plant but can be transported by people, wildlife, 

livestock, vehicles, and in soil, crop seed, and contaminated hay. Gravel pits, soil stockpiles, 

powerlines, grain elevators, railroad and equipment yards are important seed distribution points.

This species infests meadows, forests, and lower elevation rangelands, where it out-competes 

native plant species. It is capable of invading well-managed rangeland. Forage production for 

livestock and wildlife is decreased, erosion is increased, and stream sedimentation is increased 

(Carpinelli 2005). Spotted knapweed impacts native vegetation through a combination of resource 

competition and allelopathy, although recent research may be beginning to demonstrate that 

allelopathy is not as strong as was previously reported (Duke, et al., 2009).

Repin, a compound that is neurotoxic, damages the brains of horses that graze this species (TNC,

2005). It is not toxic to sheep, goats, or cattle.

A report by an employee of the Idaho Panhandle National Forest in 1997 raised the question of 

carcinogenicity of spotted knapweed sap. One day was spent pulling this plant bare-handed; after 

several months aggressive tumors developed that required amputation of two fingers. This case 

was followed up with the doctor at the University of Washington, who believed there is a 

compound in knapweed that causes cancer. This compound may also exist in diffuse knapweed 

(TNC, 2005; Carpenter & Murray, undated b).

In Arizona, there are infestations along Highways 89A and 179 in Sedona, on Northern Arizona 

University campus, along Lake Mary Road, and in the vicinity of Prescott (USFS, 2004, Feb.). It 

also occurs north of the Grand Canyon in the Arizona Strip, and not far north of the Tonto NF

above the Mogollon Rim (CRISIS, 2005). There is an unconfirmed report of spotted knapweed 

growing on the Pleasant Valley Ranger District.

Diffuse knapweed 

Centaurea diffusa

The origin of diffuse knapweed is the Mediterranean region of Europe. It was probably 

introduced to North America as a contaminant in alfalfa seed from the Middle East or in hybrid 

alfalfa seed from Germany (Maddox, 1979). It is one of the dominant rangeland weeds in North 

America, infesting over 3 million acres of rangeland in the western United States, with the area 

infested increasing at a rate of 18 percent a year (Carpenter & Murray, undated b). It often 
Appendix A

12 EA for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest

invades disturbed areas, but is able to compete easily in well-managed rangelands (Duncan,

2005).

Diffuse knapweed is a many-branched annual or short-lived simple perennial ranging in height 

from 1 to 2 feet at maturity. Basal leaves are finely divided; stem leaves are entire and smaller 

than basal leaves. It flowers from June through September with a white to purple flower.

Characteristic floral bracts are yellowish green with a light brown, comblike margin. These bracts 

are tipped with a definite slender spine (Roche & Roche, 1999).

Spotted and diffuse knapweed seeds exhibit three germination patterns: non-dormant seeds that 

germinate with or without light exposure, dormant seeds that germinate in response to red light, 

and dormant seeds that are not light sensitive. All germination types occur on each plant. Seeds 

often disperse when stems break off near the ground and the entire plant tumbles along with 

wind.

There is some disagreement in the scientific community if diffuse knapweed produces an 

allelopathic chemical that efficiently suppresses growth of other species) (Roche and Roche 

1999). Diffuse knapweed does tend to grow in monotypic stands; whether this is due to 

allelopathy or its unpalatability is a subject of discussion. Its spines can cause injury to grazing 

animals that happen to ingest it. It also causes increased soil erosion and reductions in wildlife 

populations (Roche & Roche, 1988). 

On the Tonto NF, this species has been documented growing at the Pleasant Valley Airport, the 

Pleasant Valley Ranger Station, along Cherry Creek, and along Highway 288 at Board Tree 

Saddle south of Young. There are many small infestations on the Pleasant Valley Ranger District.

Diffuse knapweed is common on private lands in Young.

Malta starthistle

Centaurea melitensis

Malta starthistle was introduced to the southwestern U.S. from Europe as a seed contaminant. It is 

very similar to yellow starthistle in appearance, and is often mistaken for it. Like yellow 

starthistle, leaves extend down the stems, giving the stem a winged appearance. A major 

difference between the two starthistles is length of spines on the flower bracts: those of yellow 

starthistle are usually approximately an inch in length, while Malta starthistle spines are normally 

less than 1/2 inch long. Unlike yellow starthistle also, Malta starthistle seeds appear to have 

longer longevity in the soil: Malta starthistle seed lives for over 3 years in the soil, making it 

potentially more difficult to eradicate.

Malta starthistle has been implicated in case reports of “chewing disease” of horses. Ingestion of 

significant quantities can cause this disease, which is characterized by fatigue, lowered head, an 

uncontrolled rapid twitching of the lower lip, tongue-flicking, involuntary chewing movements, 

and an unnatural open position of the mouth. Poisoning occurs after a horse has ingested 60 to 

160 percent of its body weight over a two-month period (Panter, 1990, 1991). Toxicity effects are 

cumulative and irreversible. In most cases, poisoning occurs where horses had little or no other 

palatable feed available to them (Schalau, 2005; UNCE, 2004).

Malta starthistle is rapidly expanding its range in Arizona. In 1972, it was already reported in 

Apache, Yavapai, Maricopa, Pinal, Graham, Pima, and Cochise counties, but was not so serious 
Appendix A

EA for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest 13

as to be declared a noxious weed (Parker, 1972). It is becoming very common in urban settings in 

central Arizona, is now found in the far eastern portion of the state, south of Duncan, and in the 

Tucson area. This plant is also very widespread and spreading rapidly at low elevations on the 

Tonto NF. To date, it has been documented below 3,000 feet elevation, with a few exceptions. It 

grows densely along Highway 188 from Highway 87 through Punkin Center to Roosevelt Lake. It 

has spread to the east side of Roosevelt Lake to the A-Cross Road, west to Camp Reno, and many 

other sites in Tonto Basin. Patches can be found along Highway 60 from Apache Junction to 

Florence and Oak Flat east of Superior. In the spring of 2005 it was pulled from a small site at the 

Cave Creek Ranger Station horse pasture and at Bartlett Lake. It has spread from the Horseshoe 

Recreation Area to endangered Arizona cliffrose habitat near Lime Creek. Other mapped 

locations on the Cave Creek Ranger District include Cartwright Basin and along Forest Road 41.

Forest Road 41 is a major access point to the Forest’s west side from the northwest Phoenix 

metro area. Malta starthistle was recently identified growing in abundance on state land west of 

the Forest’s boundary on FR41, on the west end of FR41 on the Tonto NF, and in the private 

landowner’s pastures and corrals in that same area. This infestation was treated with aminopyralid 

by the State Land Department soon after it was discovered. Infestations on adjacent Forest 

Service land have not been treated. 

Malta starthistle is common throughout the entire Phoenix metropolitan area, and in Cave Creek 

and Carefree. The farthest north and highest elevation site on the Tonto NF is at Shumway 

Millsite (4,780 feet), where it grows next to yellow starthistle (Fenner, 2005b). It has also been 

documented near Young, Arizona (SWEPIC, 2005).

Yellow starthistle 

Centaurea solstitialis

Yellow starthistle originated from southern Europe, and first entered the United States shortly 

after the 1849 gold rush. It was imported as a contaminant in alfalfa hay. At that time, the only 

place California imported alfalfa from was Chile. It had been spread to Chile in the 1600s from 

Spain. By 1958, it infested over a million acres in California. Today, there are an estimated 

16 million acres of yellow starthistle in California, and a couple of additional million acres in 

other western states. It has spread to 23 of the 48 contiguous states, as far east as New York 

(DiTomaso, 2001).

Yellow starthistle is a winter annual that is a member of the knapweed complex in the sunflower 

family. It grows about 2 to 3 feet tall and has yellow flowers. Leaves extend down the edges of 

the stems, giving the stems a winged appearance. Inflorescences have bracts with stiff, sharp 

spines that are about an inch long. A single starthistle plant has the potential to produce up to 

150,000 seeds. Germination occurs either in the fall or spring; the young plant has a rosette 

growth form. As plants mature, a flower stalk elongates from the center of the rosette.

Although studies show that some seeds can remain viable for up to 10 years (Callihan, et al.,

1993), studies done in California under natural conditions demonstrated that 95 percent of the 

seeds had either germinated or were damaged after only 2 to 3 years in the soil (Joley, et al.,

1992).

This plant has the ability to invade rangelands, pastures, croplands, and roadsides throughout the 

West, especially those with deep, loamy soils. The competitive success of yellow starthistle is 

directly related to its ability for rapid growth and capture of water, nutrients, light, and space.
Appendix A

14 EA for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest

This species displaces native plant communities, reduces plant diversity, and accelerates soil 

erosion and surface runoff. It can form solid stands that drastically reduce forage production for 

livestock and wildlife. Its ability to deplete soil moisture has been compared to a loss of 15 to 25

percent of annual precipitation (Jetter, et al., 2003).

Yellow starthistle is poisonous to horses, causing the same nervous disorder that Malta starthistle 

causes. Livestock can be injured eating even small amounts of yellow starthistle, if forced to feed 

on the spiny portions of the plant. Animals and humans normally avoid heavily-infested sites due 

to the spiny nature of the mature plants.

Human activities are the primary mechanisms for the long distance movement of yellow 

starthistle seed. Seed is transported in large amounts by road maintenance equipment and on the 

undercarriage of vehicles. The movement of contaminated hay and uncertified seed are also 

important long distance transportation mechanisms. Once at a new location, seed is transported in 

lesser amounts and over short to medium distances by animals and humans.

A 1972 publication entitled “An Illustrated Guide to Arizona Weeds” states that yellow starthistle 

was unknown in Arizona (Parker, 1972). Since that time, it has become well-established in 

central Arizona, with hundreds of acres of dense infestations in the communities of Flagstaff, 

Camp Verde, Payson, Star Valley, and Young.

On the Tonto National Forest, this plant currently grows mainly on the higher elevation ranger 

districts – Payson and Pleasant Valley. Infestations have also been documented in Tonto Basin at 

elevations below 3,000 feet.

Rush skeletonweed 

Chondrilla juncea

Rush skeletonweed is native to Europe, northern Africa, and central Asia. It was first introduced 

to eastern North America through contaminated seed, animal bedding or fodder, in 1872. It was 

first detected on the west coast in 1938. Today it infests an estimated 8.4 million acres in the 

United States. It invades ponderosa pine, chaparral, piñyon-juniper, and mountain grassland 

habitats.

Rush skeletonweed is a perennial or biennial herbaceous plant, growing to 16 to 60 inches tall.

Plants exist as basal rosettes until flowering. The leaves, stem and roots exude a milky sap when 

cut. The plant grows a long slender taproot that can extend over 6 feet into the soil, reaching into 

fissures in bedrock. Lateral roots may produce buds and rosettes. Rush skeletonweed exhibits 

obligate apomyxis (reproducing without pollination), so that populations are normally not 

genetically diverse. Infestations can be dense, with 2 to 6 rosettes per square foot measured on 

dry sites in the western U.S. While a single plant can produce 10,000 to 20,000 seeds in a season, 

drought severely limits seed production and viability of seeds. Some experiments have 

demonstrated seed to be viable under certain optimum conditions for up to 5 years; however, 

most seeds exhibit no dormancy and generally survive for less than 6 to 18 months in the field.

Seeds are adapted to both wind dispersal and dispersal through attachment to moving objects.

This species has not been documented on the Tonto NF. The only documented population in 

Arizona is at Grand Canyon National Park (CRISIS, 2005). This identification of this population 

may still need to be verified.
Appendix A

EA for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest 15

Blue mustard

Chorispora tenella

Blue mustard is a native of Russia and southwest Asia (Whitson, 2002). It was introduced to the 

U.S. in 1929, in contaminated grain seed. It infests winter annual crop fields, roadsides, and 

disturbed rangeland.

It is a leafy annual, 6 to 18 inches tall, with purple flowers. Stems and leaves are covered with 

gland-tipped hairs. Flowers, which occur in early spring are showy pale purple to bluish purple.

Viable seed can be produced as soon as 10 days after flowering begins.

In the spring of 2005, a dense patch several acres in size was observed along Highway 69 

between Cordes Junction and Prescott. CRISIS regional maps show it as growing in Prescott and 

also north of Holbrook (CRISIS, 2005). In 2008 many small infestations of this weed were noted 

in the Payson area and north along State Route 87.

Canada thistle 

Cirsium arvense

Canada thistle was first introduced to the U.S. in the early 1600s. By 1954, it was declared a 

noxious weed in 43 states. It has long been recognized as an agricultural weed. Only recently has 

it become a problem in wildlands.

It is an herbaceous perennial with an erect stem and creeping rootstock. It produces an abundance 

of bristly-plumed seed that are wind-dispersed. Most of these germinate within a year, but some 

many remain dormant in the soil for over 20 years (CDFA, 2001; Thunhorst & Swearingen,

2005a). The taproot sends out lateral roots as deep as three feet underground, which produce 

above-ground shoots. It can regenerate from root fragments less than an inch in length (Thunhorst 

& Swearingen, 2005a).

Several varieties of Canada thistle have been identified, which differ in their leaf form, growth, 

photoperiodism and susceptibility to herbicides (Hodgson, 1970).

Canada thistle is found in the northeast part of Arizona. It is very common in northern New 

Mexico. One site has been documented on the Tonto NF, near the OW Ranch, west of Canyon 

Creek, on the Pleasant Valley Ranger District. It has been treated by grubbing in 2004 and 2005, 

and the infestation is expanding.

Bull thistle 

Cirsium vulgare

Bull thistle was brought to this country from Europe and Asia, as a seed contaminant. Bull thistle 

is a biennial growing 2 to 5 feet tall. It has a short, fleshy taproot. Stems are very pubescent and 

have dark purple veins. The first year's leaves form a rosette. Second-year leaves are doubletoothed ending in a spine; are wavy; have prickles on the surface; and are pubescent on the 

underside. Stem leaves are similar to rosette leaves, but they are smaller and have longer spines. 

The tapering pointed ends of the leaves give this thistle its other common name, spear thistle.

Flower heads, made up of dark purple flowers, are 1.5 to 2.0 inches wide. Bracts surrounding the 

receptacle are narrow and spine-tipped (Zouhar, 2002b).
Appendix A

16 EA for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest

Bull thistle has been mapped in northeastern Arizona, northwestern New Mexico, and is common 

from Flagstaff south to the Mogollon Rim (CRISIS, 2005). Bull thistle is probably the least 

aggressive non-native thistle in the state. It typically appears as a few scattered individuals plants 

or populations, primarily at higher, moister sites. These individuals proliferate by shedding seed 

that mostly lands near the parent plant, but can also be wind- or air-borne. It does not compete 

well with native vegetation where the existing vegetation forms a good ground cover. Small 

infestations spread opportunistically, taking advantage of scouring floods, periodic heavy grazing, 

fires, and other soil disturbances that leave openings for seeds to land and germinate.

Seed that is located on or near the soil surface has a very short life; however, seed that is buried at 

least 6 inches may have over 50 percent viability after 3 years (Zouhar, 2002b). This induced 

dormancy at this depth could account for bull thistle infestations emerging after disturbance in 

previously uninfested sites. Bull thistle has evolved a system to encourage seed burial. Seeds have 

a nutrient-rich “peg” called an elaiosome. This external part of the seed induces ants to transport 

the seed to their underground nests, in order to feed on the elaiosome. After this part is eaten, the 

seed is discarded in another part of the underground ant nest. When the site becomes disturbed so 

that the seed is exposed to light, the induced dormant period is broken and a new infestation is 

started. Bull thistle plants in dry Canadian grasslands are often associated with ant nests (Zouhar,

2002b).

A major infestation began in Canyon Creek in the wake of the Rodeo-Chediski Fire of 2002. The 

infestation extends from the headwaters of Canyon Creek below the Mogollon Rim to the Fort 

Apache Reservation. It grows along Canyon Creek and also on forested slopes. Small infestations 

have been reported in various sites on the Payson Ranger District, many associated with burn 

piles. The Tonto NF has used both volunteer and contract crews to manually remove the Canyon 

Creek area bull thistle infestation, for the last four years.

Field bindweed 

Convolvulus arvensis

Field bindweed originated in Eurasia but has spread across the world to become a cosmopolitan 

species growing between 60o

N and 45oS latitudes. It was introduced to the eastern U.S. in the 

1700s and spread westward rapidly with construction of the railroads. It was established in the 

western U.S. by the early 1900s (Weaver & Riley, 1982).

It is a persistent, perennial vine of the morning-glory family, which spreads rhizomatously and by 

seed. An extensive root system makes total eradication nearly impossible. Lateral root growth in 

one year has been measured to average 15 feet. Lateral roots are generally within the top foot of 

soil, but one-third of the total root system grows below 2 feet. Field bindweed also produces 

extremely persistent seed. In one experiment with 55 year-old seed, 65 percent were found to be 

still viable (Brown & Porter, 1942). Seed can remain viable in the stomachs of migrating birds for 

up to 6 days, dispersing it over a distance of many miles (Lyons, 1998).

Relatively little is known of the impact of this plant on natural areas. Its extensive root system can 

deplete the top foot of soil of water to below wilting point for most species. It can choke out 

native grasses and forbs, especially in riparian areas.

Foliage contains alkaloids that can cause intestinal problems in horses grazing on heavily infested 

pastures (CDFA, 2005).
Appendix A

EA for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest 17

This plant has mainly been found on roads, near fields and other disturbed areas within the Tonto 

National Forest, on the Payson and Pleasant Valley ranger districts.

White bietou

Dimorphotheca cuneata

This plant is a perennial half-shrub, native to South Africa, but can be easily purchased in seed 

form from anywhere in the world. There are no records regarding this plant as an invasive species 

in the U.S. A related species, D. sinuata, is documented as occurring in California as an invasive 

plant (Skurka, 2005a). This species is an annual, commonly called an African daisy.

The Tonto NF has two populations of this plant; one that has spread from an ornamental planting 

approximately 20 years ago on private lands south of the Globe Ranger Station, and another mile

to the east, along a system road. This plant currently occupies 40 acres of the National Forest.

This half-shrub, with extremely attractive large white flowers, is widespread in yards and canyons 

between Six Shooter Canyon and National Forest lands to the west.

Common teasel 

Dipsacus fullonum

Teasel is a European plant introduced to the U.S. in the 1700s (WDNR, 2004). It is commonly 

used, and spread, in dried flower arrangements. It is also sold by nurseries as a flowering plant.

It grows as a short-lived perennial or biennial. It spends one or more years as a rosette before 

sending up a flower stalk. Teasel's unique inflorescence makes the plant readily identifiable when 

flowers or seedheads are present. Tiny purple flowers in an ovoid inflorescence are each 

subtended by a long spiny bract. Infestations occur in sunny riparian areas.

Teasel produces an abundance of seeds. A single teasel plant can produce over 2,000 seeds; up to 

30 to 80 percent of the seeds may germinate. Seeds may remain viable for at least 2 years. Seeds 

typically don't disperse far; most seedlings will be located near the parent plant. Streamflow in 

riparian areas can carry them some distance from the original infestation.

There are only a few known isolated populations of teasel in northern Arizona. One patch is at 

Watson Woods on Granite Creek in the Prescott area (USFS, 2004, Feb.). CRISIS maps show 

another infestation elsewhere in Yavapai County. Teasel has been documented on the Tonto NF

at Shumway Millsite, south of Payson, on the Payson Ranger District. Employees at Payson 

Ranger District have reported seeing it in the vicinity of Sharp Creek Campground. These 

infestations are all associated with riparian areas.

Russian olive 

Eleagnus angustifolia

Russian olive is a fast-growing tree, reaching a height of 10 to 25 feet at maturity (Whitson,

2002). Trunks and branches are covered with 1 to 2 inch thorns. Leaves are narrow, 2 to 3 inches 

long. Clusters of yellow flowers bloom in early summer; fruit resembles small reddish-brown 

olives. Birds and small animals eat the fruits, which aids in dispersal of the seeds. Its large seeds 

remain viable for up to 3 years and are capable of germinating over a broad range of conditions 
Appendix A

18 EA for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest

(Shafroth, et al., 1995). Also, seeds germinate anytime from fall to spring, giving Russian olive a 

competitive advantage over native riparian trees. Russian olive also spreads vegetatively (Tu,

2003).

It was introduced from Europe in the early 1800s as a desirable ornamental shade tree. It is now 

invasive in 17 western states. It is especially invasive in riparian woodlands, taking advantage of 

scouring events to replace cottonwood and willow trees (Tu, 2003). It has nitrogen-fixing roots, 

which enable it to grow on bare mineral substrates and dominate riparian vegetation where 

overstory cottonwoods have died. Bird species richness is higher in native riparian vegetation 

than where Russian olive dominates (Muzika & Swearingen, 2005a).

It can survive drought conditions, so is adapted to ephemeral riparian drainages that are common 

on the Tonto NF. Dense thickets of Russian olive increase the occurrence of catastrophic 

wildfires in riparian areas, due to their heavy fuel-loading (Caplan, 2002).

Russian olive has been found in the northeast quadrant of Arizona (CRISIS, 2005), and also in 

Prescott Valley, Chino, Camp Verde, and east of Flagstaff (USFS, 2004, Feb.). It has been 

documented very near the Tonto NF, on private land in Houston Creek in Star Valley.

Quackgrass 

Elymus repens

Quackgrass is a cool-season, exotic, perennial, rhizomatous graminoid. Its stems are erect 

growing to 1 to 3 feet in height. Rhizomes can grow 23 inches or more from the main shoot 

before sending out stems (Batcher, 2002). Quackgrass propagates mainly by rhizomes, but also 

reproduces by seed. Seed production, however, is reported to be as low as 25 viable seeds per 

plant per season. The seeds can remain viable for 1 to 6 years. Viability can be maintained even 

after passing through the digestive tract of most farm animals (Reidy & Swanton, 2001).

Quackgrass is native to Europe and western Asia. It has been reported growing in every state of 

the United States (Batcher, 2002).

Quackgrass produces chemicals that inhibit nearby plant growth. As a cool-season grower, it can 

usurp water and soil nutrients through the soil profile, thus suppressing growth of later, warmseason grasses. 

To date, this is an uncommon weed in Arizona. It has only been documented near Flagstaff, and 

in the Grand Canyon National Park. It has been found on one site on the Tonto National Forest, 

on the Pleasant Valley Ranger District.

Weeping and Lehmann’s lovegrass 

Eragrostis curvula & E. Lehmanniana

Although there is a native lovegrass species in Arizona (E. intermedia), these 2 species of 

Eragrostis are introduced from South Africa.

These plants were introduced as part of range restoration/soil conservation programs in the 

Southwest, and thousands of acres were planted with them in the 1930s (Moser & Crisp, 2003).

In the mid-to-late 1900s, these species were commonly included in seed mixes used after fires, 
Appendix A

EA for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest 19

highway construction/reconstruction, and other ground-disturbing activities, such as powerline 

road construction. Lehmann’s lovegrass thrives best at elevations from 3,000 to 4,500 feet;

weeping lovegrass grows in Arizona from 4,900 to 6,500 feet. They were planted with forage 

value in mind; however, they are not as palatable as native perennial grasses, and tend to outcompete them. Although they are classified as warm-season growers, they produce more green 

herbage in the winter and early spring than native grasses. This active growth during a time when 

native warm-season grasses are still dormant is key to their dominance in a grassland community 

years after planting (Moser & Crisp, 2003; Uchytil, 1992; & Gucker 2009a).

When native grassland and pastures seeded to Lehmann’s and weeping lovegrass were compared, 

the two site types differed consistently in that the planted exotics grew in monospecific stands 

and native grasses did not. Total native herbaceous canopy, species richness, shrub density and 

shrub canopy were significantly reduced on plots seeded to the lovegrasses. Small birds that nest 

in grasslands will use Lehmann’s lovegrass, but nest more frequently in native grassland if it is 

available (Uchytil, 1992).

Lehmann’s lovegrass reseeds itself quickly after disturbance, and tends to replace native grasses 

where it has been planted. It has replaced Arizona cottontop, threeawn grasses, and grama grasses 

over much of the Santa Rita Experimental Range in Arizona (Cable, 1971). Weeping lovegrass 

produces up to 1,000 seeds per seedhead, but rate of spread by seeds is very slow, and this plant 

does not actively colonize adjacent nonplanted sites. Weeping lovegrass should not be planted 

after wildfires for restoration, if management objectives are to maintain native plant communities.

Although weeping lovegrass is not particularly invasive, once it is planted, it remains in place for 

a very long time (Gucker, 2009a).

Desert shrublands that have been invaded by Lehmann’s lovegrass experience much more intense 

burning during wildfires. Most native desert plants and cryptogams are not adapted to intense and 

frequent fires; species composition changes over time in sites that have been invaded by this and 

other exotic perennial grasses such as buffelgrass.

Lehmann’s lovegrass seeds are initially dormant, requiring 6 to 9 months of afterripening. They 

need some type of dry heat to scarify their seedcoat and increase water uptake by the seed to be 

able to germinate. Shading inhibits germination, as the seeds also require exposure to red light to 

germinate (Uchytil, 1992). Weeping lovegrass exhibits facultative apomyxis; that is, seeds do not 

have to be fertilized to grow into new plants. Weeping lovegrass seedlings must have dependable 

moisture after they germinate. Less than 20 percent of newly germinated seedlings survived one 

day of dessication and none survived 3 days of dessication (Uchytil, 1992).

On the Tonto NF, these grasses have been extensively seeded along highways, powerline 

corridors, and aerially seeded after fires. In 1951, weeping lovegrass was aerially seeded in the 

Pinal Mountains after a wildfire (Gucker, 2009a). In 1990, it was included in the seed mix that 

was applied to the entire area of the Dude Fire, a 28,000 acre fire that burned a swath about 3 

miles wide and 14 miles long across the face of the Mogollon Rim on the Payson Ranger District.

Leafy spurge 

Euphorbia esula

Leafy spurge was transported to the U.S. possibly as a seed impurity in the early 1800s. First 

recorded from Massachusetts in 1827, leafy spurge spread quickly and now occurs across much 
Appendix A

20 EA for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest

of the northern U.S., with the most extensive infestations reported in Montana, North Dakota, 

Nebraska, South Dakota, and Wyoming (Thunhorst & Swearingen, 2005b). In 1996 there were 

2.5 million acres infested with leafy spurge in the U.S. and Canada (Biesboer, 1996).

Leafy spurge is an erect, branching, perennial herb 2 to 31⁄2 feet tall, with smooth stems and 

showy yellow flower bracts. Stems frequently occur in clusters from a vertical root that can 

extend many feet underground. Stems and leaves have a white milky sap that is a skin irritant.

The leaves are small, oval to lance-shaped, somewhat frosted and slightly wavy along the margin. 

The flowers of leafy spurge are very small and are borne in greenish-yellow structures surrounded 

by yellow bracts.

Leafy spurge reproduces by seeds that have a high germination rate and may remain viable in the 

soil for at least seven years. Its seed capsules open explosively, dispersing seed up to 15 feet from 

the parent plant and may be carried further by water and wildlife. Approximately 99 percent of 

seeds germinate within two years (Biesboer, 1996). Most seeds germinate in the spring, but 

germination and establishment does occur throughout the growing season. Leafy spurge also 

spreads vegetatively at a rate of several feet per year. The root system can reach 15 or more feet 

deep and may have numerous buds.

The milky sap produced by leafy spurge will cause a severe skin rash in humans. This weed is 

also poisonous to most livestock, with the exception of sheep, which can be used to control it. If 

horses are permitted to walk in areas with leafy spurge, the sap will cause severe blistering and 

hair loss on their feet (Nova Scotia Department of Agriculture and Fisheries, 2003). It is reported 

to cause severe irritation of the mouth and digestive tract in cattle, which may result in death 

(Whitson, 2002).

When leafy spurge infests pastures, herbage production can be reduced by as much as 75 percent

(Lym & Messersmith, 1985). Cattle will avoid grazing an area with as little as 10 percent cover of 

leafy spurge (Hein & Miller, 1992).

Extracts from the roots of leafy spurge are leached into the soil wherever the weed grows. These 

extracts inhibit the germination and growth of other plants in the surrounding area (Nova Scotia 

Department of Agriculture and Fisheries, 2003).

Leafy spurge is an aggressive invader and, once present, can completely overtake large areas of 

open land. Because of its persistent nature and ability to regenerate from small pieces of root, 

leafy spurge is extremely difficult to eradicate (Thurhorst & Swearingen, 2005b).

The Environmental Impact Statement for treatment of invasive plants on the three northern 

Forests in Arizona cites one infestation on the Coconino National Forest and two on the Kaibab 

National Forest (USFS, 2004, Feb.). This plant has not been documented on the Tonto NF.

Sweet resinbush 

Euryops subcarnosus ssp. vulgaris

Sweet resinbush is a perennial shrub, growing up to 3 feet in height, native to South Africa. It was 

collected by SCS Regional Director F.J. Crider in 1934 for introduction to the Southwest to 

control high erosion that was occurring during the 1930s (Pierson & McAuliffe, 1995). A 1928 

publication, The Flowering Plants of South Africa, claimed sweet resinbush to have good forage 
Appendix A

EA for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest 21

value, especially for sheep, to be drought-resistant, and to propagate easily. Two out of three 

claims were correct. Recent research has shown that most species of Euryops contain noxious 

chemicals so that they are not only unpalatable, but toxic to wildlife and livestock (Schalau,

2001).

Resinbush was planted in many locations throughout the Southwest by Civilian Conservation 

Corps crews doing erosion control projects. Seeds and young plants were also made available by 

SCS to anyone who would plant them (Pierson & McAuliffe, 1995).

The largest population today in Arizona (over 5,000 acres) is on Fry Mesa south of Safford 

(Henson, 2006). In 1998 it was discovered growing on the Santa Rita Experimental Range in 

southern Arizona (Howery, et al., 2003).

Small (less than 1 acre in size) patches of sweet resinbush, remnants of CCC erosion-control 

plantings, have been mapped south of the Globe Ranger Station, in the same area as the 

Dimorphotheca population. One infestation of about 3 acres remains in Tonto Basin west of 

Highway 188; the largest population on the Tonto NF is 22 acres on the north side of 

Highway 60, north of the Miami cemetery. Plant density at this site averages nearly 3,400 plants 

per acre. In some patches it has crowded out all other plants (Brock, 2008). This site has remained 

the same size for four years, but seems to have increased in density (Fenner, 2008). It also grows 

east of the cemetery on slopes and two miles down Bloody Tanks Wash toward Miami. All of 

these populations are associated with CCC civil works projects of the 1930s. Many of the 

checkdams constructed by the CCC are still functioning, including some very impressive ones in 

Bloody Tanks Wash west of Globe/Miami. The Tonto NF is working to manually remove all of 

its resinbush infestations.

Invasion by sweet resinbush has produced dramatic changes in some of the semi-arid grasslands 

and shrublands where it was planted. It creates monocultures, excluding normally prevalent halfshrubs like Calliandra, shrubby buckwheat, and even snakeweed. Elimination of grasses leads to 

a dramatic increase in exposure of bare soil, and increased soil erosion (Pierson & McAuliffe,

1995). In a sweet resinbush site in Marijilda Canyon, the bare soil created by the dominance of 

this species resulted in soil that moved more easily. Exposed roots and soil pedestals around bases 

of the few remaining native grasses were evident in the zone just ahead of resinbush dominance.

A sharp demarcation zone at the front of the resinbush infestation was not due to allelopathy, but 

to extremely efficient uptake of water by the resinbush, leaving none for the native plants 

(Pierson & McAuliffe, 1995).

Little is known of seed dormancy patterns, production, or longevity in the soil. Most seed falls 

underneath the parent plant and germinates there. Seed is also transported by adhering to fur or 

clothing, or by floating in streams or ephemeral washes.

Dyer’s woad 

Isatis tinctoria

Dyer’s Woad was introduced into North America from Europe late in the 17th century. It was 

cultivated as a source of blue dye (Callihan & Miller, 1999). It is a perennial or biennial herb in 

the mustard family.
Appendix A

22 EA for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest

It reproduces by seed, with most seeds falling near the parent plant. An average of 383 oneseeded pods is produced per plant (CDFA, 2005). These pods do not open, and contain watersoluble inhibitors that prevent seeds from germinating until thorough leaching occurs. Seed 

longevity has not been studied.

Dyer’s woad invades both disturbed and undisturbed areas, and seems to prefer open dry rocky 

soils. It also invades stands of other invasive plants, such as cheatgrass. It reduces forage 

availability by suppressing growth of grasses, and it is low in palatability to grazing animals. It is 

frequently spread through contaminated hay, as it grows as a weed in alfalfa fields. It is also 

moved about on contaminated equipment.

This species has not been documented on the Tonto NF, and there are no documented records for 

this species in either the CRISIS or SWEMP databases. It is known mainly in the Intermountain 

West and the northwest U.S.

Kochia

Kochia scoparia

Kochia is an annual forb brought to North America from Europe. It is now common across the 

northern U.S, and is working its way southward. In Arizona there are many documented 

observations in the northeast quadrant of the state. It was observed on the Fort Apache 

Reservation north of the Salt River during a weed survey of the river in the spring of 2005 

(Fenner, 2005).

It has a thick taproot, from which it breaks off when the plant is mature. It disperses seeds by 

tumbling like Russian thistle. One plant typically produces nearly 15,000 seeds (WSNWCB,

2005). Seeds on the soil surface typically survive 1 to 2 years, but buried seeds may remain viable 

for over 3 years (Zorner, et al., 1984).

It withstands drought well, becoming a dominant plant in the Midwest during the dust bowl years.

It is documented to possess allelopathic properties that affect even its own seedlings (Wali, 1999). 

Kochia scoparia causes hepatotoxicity with photosensitization, renal disease and 

polioencephalomalacia to livestock. Another species of kochia, K. prostrata, is sold as a forage 

crop for livestock. K. prostrata is a drought-tolerant perennial sub-shrub. Both species have been 

used for livestock forage (kochiaseed.com, 2003).

Oxeye daisy

Leucanthemum vulgare

Oxeye daisy is a perennial forb in the sunflower family that has naturalized from Europe into all 

50 states (USDA NRCS, 2004). Spread is assisted by seed companies, who sell seed packets even 

in states where the plant is listed as a noxious weed (WSNWCB, 2000). It also spreads 

vegetatively by rhizomes (Alvarez, undated).

Oxeye daisy is able to produce seed its first summer of growth. It is a prolific seed producer when 

it is growing in moist soil. Most oxeye daisy seed remain viable for 20 years in the soil, and 

remain viable after passing through the digestive tracts of animals (Alvarez, undated).
Appendix A

EA for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest 23

Oxeye daisy has a white flower with a yellow center, and grows to a height of 30 inches. It often 

invades overgrazed or otherwise disturbed ground. It can tolerate drought and frost, but prefers 

moist, unshaded sites.

In areas of heavy infestations, there is more bare soil than adjacent native meadows, which 

increases the potential for soil erosion (Olson & Wallander, 1999). Plants are resistant to grazing, 

and since cattle normally avoid eating oxeye daisy, pastures with this species tend to deteriorate 

in range capacity through time (WSNWCB, 2000).

It has not been documented on the northern three National Forests in Arizona, but does grow in 

Flagstaff and Kachina Village south of Flagstaff (USFS, 2004, Feb.). It was recently identified 

growing inside an elk exclosure along Canyon Creek, on the Pleasant Valley Ranger District 

(Fenner, 2005). The exclosure fence was recently constructed by the Arizona Game & Fish 

Department to control overgrazing by elk in this popular fishing area. 

Dalmatian toadflax, Yellow toadflax 

Linaria dalmatica, Linaria vulgaris

Both toadflaxes are native to the Mediterranean region. Dalmatian toadflax was introduced to the 

west coast of the U.S. in 1874 for use as an ornamental. Yellow toadflax was brought to New 

England from its native south-central Eurasia in the late 1600s as an ornamental and medicinal 

plant. Today it is still sold as “butter and eggs,” “Jacob’s Ladder,” or “wild snapdragon.” Seed of 

Dalmatian toadflax is also sold by garden catalogs and nurseries.

Dalmatian toadflax is a creeping perennial herb that grows up to three feet tall. It has grayishgreen alternate leaves that clasp the stem. Flowers are yellow and very similar to snapdragon 

flowers. This plant reproduces by root sprouts and an enormous number of seeds. While it is 

attractive and not thorny, it does tend to take over wildlands, replacing other species of more 

value to wildlife, livestock, and erosion control. A single Dalmatian toadflax plant can produce 

up to 500,000 seeds in one growing season (Robocker, 1970). Seed of both toadflaxes can remain 

viable in the soil for over 10 years. Dalmatian toadflax patches can totally disappear, only to 

reestablish after several years, from either buried seeds or vegetative buds on the roots (Robocker,

1974).

Yellow toadflax is also a perennial forb with a woody base. Leave are narrower than those of 

Dalmatian toadflax. Flowers are borne in axils of upper leaves, as in Dalmatian toadflax;

however, flowers of yellow toadflax have a longer spur.

Both toadflaxes have adapted through centuries of grazing in Europe, to survive highly disturbed 

habitats. They will move from small sites of natural disturbance into pristine rangeland. Once 

toadflax invades native rangeland, it is very difficult to stop its spread. Toadflaxes commonly 

displace existing plant communities and associated animal life. Consequent loss of forage 

adversely impacts livestock and wildlife. Where it replaces sod-forming or bunch grasses, erosion 

increases.

Yellow toadflax has been reported to be toxic to cattle, but this is rare, since cattle normally avoid 

it (Lajeunesse, 1999). All Linaria species are toxic to livestock because they contain a glucoside 

antirrhinoside, a quinoline alkaloid, and peganine (Jeanneret & Schroeder, 1992).
Appendix A

24 EA for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest

Dalmatian toadflax is very common around Flagstaff. It is widespread in ponderosa pine forests 

on the Kaibab, Coconino, and Prescott national forests (USFS, 2004, Feb.). On the Tonto NF, it 

grows at the Payson Ranger District Hot Shot Base and along Highway 87 between Payson and 

Rye (Fenner, 2005b). Arizona Department of Transportation treated the infestation on Highway 

87 with herbicides for several years, until recently. It was nearly eradicated, but is now returning.

In 2003, a small infestation was discovered growing on a low rocky terrace above the Verde 

River, one mile downstream from Childs, on the Cave Creek Ranger District. It appeared to be 

associated with a trespass road into the Mazatzal Wilderness. This is the lowest elevation where 

Dalmatian toadflax has been documented in Arizona (Northam, 2004). Yellow toadflax has not 

been documented on the Tonto NF.

Purple loosestrife 

Lythrum salicaria

Purple loosestrife is native to Eurasia and was first reported from the northeastern coast of North 

America in 1814 (Bender, 2001).

Lythrum salicaria is a stout, erect perennial herb with a strongly developed taproot. The plant 

ranges in height from 11⁄2 to 8 feet (Bender, 2001; Whitson, 2002). The inflorescence is spikelike, 4 to 16 inches long. Petals are usually magenta, but white or light pink flowers are common 

(Bender, 2001). It is usually associated with riparian areas. The semi-woody aerial shoots die in 

the fall, but persist for one to two years making stands of purple loosestrife very dense. New 

shoots arise the following spring from buds at the top of the rootstocks (Bender, 2001).

The seeds are small, weighing 0.06 mg each. Dispersal is mainly by wind, but seeds can also be 

transported on the feet of waterfowl or other wetland animals. Red-winged blackbirds have been 

observed eating the seeds. Humans carry seeds inadvertently on clothing and shoes. The seeds 

and cotyledon stage seedlings are buoyant and can be dispersed by water currents. The seed bank 

potential is enhanced by the high viability of the seeds. After two years in a lake, 80 percent of 

seed viability was retained (Bender, 2001). Purple loosestrife seed germinates in such high 

densities that it out-competes native seedlings. It tends to build up biomass from year to year, 

enabling it to move into open water.

Purple loosestrife is considered an important weed of wetlands in most of North America. 

Reservoirs with widely fluctuating water levels provide excellent habitat for it (Rawinski & 

Malecki, 1984).

The only known populations of purple loosestrife in Arizona are on the Apache-Sitgreaves 

national forests (Crisp, 2000).

Yellow sweetclover 

Melilotus officinalis

Melilotus species are native to the Mediterranean area through central Europe to Tibet. They were 

reported in North America as early as 1664 and have been extensively used by agriculturalists as 

forage crops, soil builders (they are in the legume family, that fix nitrogen in the soil), and as a 

nectar source for honey bees. The sweetclovers have spread from cultivation and thrive in waste 
Appendix A

EA for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest 25

places and roadsides throughout the U.S. and Canada (Eckardt, 1987). Yellow sweetclover can 

act as a winter annual or a biennial (Whitson, 2002).

Rainwater runoff and stream flow are probably the most important means of seed dispersal, 

although wind can blow seeds several feet. Newly mature seeds will be soft, but as they dehydrate 

they become temporarily "hard" or impermeable, and can remain viable in this state for many 

years. Hard sweetclover seeds can remain viable in the soil for over 20 years (Eckardt, 1987).

Other sources state seeds could remain viable in the soil up to 50 years (USGS, undated). Each 

plant can produce 14,000 to 350,000 seeds. Yellow sweetclover does not reproduce vegetatively.

Yellow sweetclover has a bitter taste, making it less palatable to cattle than other legumes. It is 

more palatable in early spring and summer, becoming woody in late summer and fall (Gucker,

2009b).

This plant is fairly widespread through Arizona – it has been documented at the Grand Canyon, 

and in Cochise, Pinal, Maricopa, Apache, and Yavapai counties (Litzinger, et al., 2004). On the 

Tonto NF, it has been used in seed mixes, and has lingered on in wetter sites. It is very common 

in the riparian zone along the Verde River, on the Cave Creek Ranger District.

Oleander 

Nerium oleander

This is a very commonly used landscaping plant in the Phoenix urban area. There are two sites 

where it has naturalized on the Tonto National Forest. Several clumps of it have attained great 

height, growing in Arnett and Telegraph Canyons, near Boyce Thompson Arboretum (Grove,

2004). Another large individual plant was found growing in Camp Creek, on the Cave Creek 

Ranger District, apparently naturalized from a nearby recreational residence (Loomis, 2006;

Nelson, 2006; & Fenner, 2005b). There is an as-yet unconfirmed report of oleander growing 

along the shore of Canyon Lake near Horse Mesa Dam.

Oleander has not been considered to have invasive potential until recently. A Red Alert was 

issued by the California Invasive Species Council for this plant in 2000. It had been found along 

the Sacramento floodplain near Redding, and riparian zones in southern California (Tu &

Randall, 2000). 

The Arizona Daily Star included oleander in a list of ornamental plants that were becoming 

invasive in Saguaro National Park (McKernan, 2005).

Oleander is native to the Mediterranean region, where it grows in ephemeral washes. Its pods 

contain seeds that have plumes of hairs for wind dispersal.

All parts of the plant are extremely poisonous, containing 10 different cardiac glycosides. These 

compounds induce cardiac arrhythmia and eventual death. The lethal dose of green oleander 

leaves for cattle and horses is 0.005 percent of the animal’s body weight. Inhalation of smoke 

from a burning oleander also can cause poisoning (Skurka, 2005b).
Appendix A

26 EA for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest

Globe chamomile

Oncosiphon piluliferum

This plant is a close relative of Pentzia incana, another introduction from South Africa. It is an 

annual plant, which has escaped cultivation in the U.S. and also in western Australia (Rayner, 

2009). Beginning in 2005, it was observed at several different places in Arizona, possibly 

naturalized from plantings. To date, it has been documented growing in abundance along I-17 

from north Phoenix to the New River crossing, spreading up to 3⁄4 mile into the desert on both 

sides of the Interstate (Fenner, 2008; Northam, 2005). By 2008, it has spread throughout the town 

of Cave Creek. Isolated patches of globe chamomile have also recently been identified near 

Skunk Tank Ridge south of Cave Creek on the Cave Creek Ranger District, at the Cave Creek 

Ranger Station, at the Sonora Desert National Monument, at Pinal City near Superior, along 

Highway 84 west of Casa Grande, at the Extension Service demonstration garden on east 

Broadway in Phoenix, on a disturbed site four miles east of I-17 on Carefree Highway, at Ben 

Avery Shooting Range on Carefree Highway west of I-17, and growing in cultivation at the 

Desert Botanical Garden and Boyce Thompson Arboretum (Trask, 2004; Northam, 2005).

Scotch thistle 

Onopordum acanthium

Scotch thistle is native to Europe and Asia. It was introduced to the eastern U.S. in the late 1800s.

Today it can be found in most western states. It prefers moist sites, and has the potential to invade 

riparian areas. It also has been documented to replace native bunchgrasses and sod-forming 

grasses (Beck, 1999). 

It is normally a biennial, but can also grow as an annual or a short-lived perennial plant (Young &

Evans, 1969). This is a large thistle, growing to a height of up to 8 feet, with basal leaves 2 feet 

long. Leaves are spiny and covered with fine dense hairs on both sides. Flowers are 1 to 2 inches 

in diameter, pale purple to red, and flat-topped. Below the flower are spiny bracts (Beck, 1999).

Up to 90 percent of seeds are dormant when mature. A water-soluble germination inhibitor in the 

seeds ensures the plant will grow in moist sites, and prolongs the seed’s life in the soil. Most 

seeds germinate near the parent plant, although transport by human activities and animals does 

occur. 

This plant can create a tall, dense, spiny obstruction to human and animal movements.

Scotch thistle is common in the Four Corners area, the Arizona Strip, and along the interstate 

system around Flagstaff. There is one known population on the Prescott National Forest 

(SWEPIC, 2005; USFS, 2004, Feb.). In 2004, the first infestation of this plant was documented 

on the Tonto NF, growing in Strawberry at the Highway 87 bridge.

African rue 

Peganum harmala

African rue is a many-branched perennial that has an aggressive, woody root system. Height 

rarely exceeds 1 to 1.5 feet. Stems are fleshy. When crunched, the stems have a bitter, acrid taste 

and a disagreeable odor. Leaves are alternate, smooth, and divided into linear segments. Flowers 

consisting of five white petals are borne singly in leaf axils along the stems.
Appendix A

EA for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest 27

African rue’s origin is North Africa. The first reported infestation in the United States was near 

Deming, New Mexico, in the 1920s (Texasinvasives.org, 2008). It was brought in by a farmer,

who wanted a new plant that would yield a red dye for wool yarn (Davison & Wargo, 2001).

African rue is poisonous to cattle, sheep, horses, and humans. Other species may be vulnerable as 

well. The seeds, fruit and young leaves are the most poisonous plant parts. Rue is an extremely 

unpalatable plant and livestock consume it only when starving or under a severe mineral 

deficiency. The early symptoms of poisoning include weakness in the hind legs, listlessness, 

salivation, and anorexia. In humans, the alkaloids present in the plant cause hallucinations and 

severe vomiting (Davison & Wargo, 2001).

The Arizona Department of Transportation recently confirmed a small infestation of African rue 

growing in Pima County along I-10 near the town of Vail. It also occurs in northwestern and 

southwestern New Mexico, California, Colorado, Nevada, and Oregon (USDA NRCS, 2011).

This species has not been documented on the Tonto NF.

Buffelgrass 

Pennisetum ciliare

Buffelgrass is native to arid regions of Africa, Asia, and the Middle East. It was introduced to 

Texas as early as 1917, but the most common variety in this country was brought to San Antonio, 

Texas, California, Arizona, and New Mexico from Kenya by the Soil Conservation Service in the 

1940s. In Tucson, it was studied at the place now known as the Natural Resource Conservation 

Service – Tucson Plant Materials Center. It was planted from the 1970s through the 1980s at sites 

around Tucson, including the Santa Rita Experimental Range, where it still grows (Yetman & 

Burquez, 1994).

It has a sprawling growth habit, with stems that can grow to four feet long, and a mass of tough 

roots that can penetrate the ground to four feet deep (Douglas King Co., 1999).

Buffelgrass is adapted to survive frequent fire. It will burn while still green, and forms new 

sprouts immediately after the fire has died. This perennial grass crowds out other desert 

vegetation or grows in areas that are normally occupied only by ephemeral spring or fall 

vegetation. It provides a continuous fuel that carries fire into the Sonoran Desert, which is not 

adapted to frequent fire.

Extensive buffelgrass invasions with their consequent frequent fire, have converted desert scrub 

communities into non-native grassland in Mexico (Burquez, et al., 2002).

This perennial warm-season grass is common in Phoenix. It is spreading onto the Tonto NF along 

Highways 60 and 87, Pima Road in Scottsdale, Cave Creek Road, and other roads. Its spread 

northward has been limited by its sensitivity to frost. In 1999 the USDA, Agricultural Research 

Service and Texas Agricultural Experiment Station registered a new cultivar they named “Frio” 

that is able to withstand and thrive in colder temperatures (Hussey & Burson, 2005). This 

development could lead to much greater spread of buffelgrass on the Tonto NF and colder areas 

to the north and west.
Appendix A

28 EA for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest

Fountain grass 

Pennisetum setaceum

Originally native to Africa and the Middle East, fountain grass has been introduced to many parts 

of the world as an ornamental grass (Benton, 2005). It is popular in many countries as an 

ornamental plant and has dispersed into wildlands across Arizona, California, Florida, Hawaii, 

Fiji, South Africa, and Australia because of sales in nurseries (Lovich, undated). 

Fountain grass is an attractive perennial grass with a densely-clumped growth form and erect 

stems that grow 2 to 3 feet high. The small flowers of fountain grass are grouped in pink or 

purple, bristly, upright inflorescences 6 to 15 inches long. Fruits are small, dry achenes with long 

bristles. Seed are wind-dispersed, and remain viable in the soil for 7 years or longer. Seeds may 

be dispersed greater distances by water, vehicles, livestock, and humans (Cal IPC, undated). The 

long-lived seeds of fountain grass make its control extremely difficult. Fountain grass is 

apomictic, which means it can reproduce by either fertilized or unfertilized seeds (Simpson & 

Bashaw, 1969).

Fountain grass is a highly aggressive, fire-adapted colonizer that readily out-competes native 

plants and rapidly re-establishes after burning. Fountain grass raises fuel loads, which increases 

the intensity and spread of a fire, and results in severe damage to native desert species including 

all species of cactus.

Fountain grass has been documented on the Tonto NF on all desert ranger districts. It grows 

profusely along Highway 60 east of Superior. It also grows along Highway 87, along the road to 

Bartlett and Horseshoe Reservoirs, and in the Salt River Recreation Area. It is commonly used for 

landscaping, and is an escaped ornamental throughout the greater Phoenix area. 

Karoo bush 

Pentzia incana

Pentzia incana was first introduced from South Africa to Arizona by the Soil Conservation 

Service, working with the Civilian Conservation Corps, in the 1930s. It was selected for its 

drought tolerance, and intended to prevent soil erosion, which was rampant during the drought of 

the 1930s. Karoo bush was planted as late as 1946 in plant trials at the Santa Rita Experimental 

Range in southeastern Arizona (Munda & Pater, 2003).

It is a small shrub in the sunflower family. Its yellow ball-like flowers appear during the 

winter/early spring. It has not exhibited a great deal of invasiveness in either of the two sites it 

has been documented on the Tonto NF, north of Oak Flat Campground on the Globe Ranger 

District, and growing in association with sweet resinbush at the Miami cemetery site. Soils in the 

site it inhabits have been severely disturbed. Both sites are associated with checkdams 

constructed by CCC crews in the 1930s.

Pentzia is advertised on some landscaping websites as a desirable plant; The State Department of 

Water Resources recommends it as a low water-use plant (Arizona Dept. of Water Resources,

2004), as does the University of Arizona’s Office of Arid Land Studies.
Appendix A

EA for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest 29

Japanese knotweed 

Polygonum cuspidatum

Japanese knotweed is an herbaceous perennial that can grow to over 10 feet in height. Stems of 

Japanese knotweed are smooth, stout and swollen at joints where the leaf meets the stem. Leaves 

are about 6 inches long by 3 to 4 inches wide, broadly oval to somewhat triangular, and pointed at 

the tip. Small greenish-white flowers bloom in the summer. Small winged fruits contain 

triangular, shiny, one-tenth-inch long seeds.

Japanese knotweed spreads quickly to form dense thickets that exclude native vegetation and 

greatly alter natural ecosystems. It poses a significant threat to riparian areas, where it is able to 

rapidly colonize after scouring floods. Once established, populations are extremely persistent.

Japanese knotweed spreads primarily by vegetative means. It may also be transported by water, 

and the tiny seeds may be wind-dispersed. It naturalizes easily from gardens; discarded cuttings 

are common routes of dispersal from urban areas.

This invasive species can tolerate a variety of adverse conditions including full shade, high 

temperatures, high salinity, and drought. It is found near water sources, such as along streams and 

rivers, in low-lying areas, waste places, utility rights-of-way, and around old homesites. It can 

quickly become an invasive pest in natural areas after escaping from cultivated gardens. 

Japanese knotweed was probably introduced to the U.S. in the late 1800s. Also known as crimson 

beauty, Mexican bamboo, Japanese fleece flower, or Reynoutria, it was first introduced as an 

ornamental and has also been used for erosion control and for landscape screening. It is now 

found throughout the eastern U.S., in several western states, and Alaska. 

This plant was recently discovered for sale at a nursery in Star Valley, east of Payson (Brock,

2004).

Sulfur cinquefoil

Potentilla recta

Sulfur cinquefoil is a perennial shrub of the rose family, native to Eurasia and North Africa. It 

grows to a height of 1 to 11⁄2 feet, with 1 to 8 unbranching stems. The entire plant is covered with 

shiny, erect hairs. A single plant can live up to 30 years. The plant has a single taproot, and may 

have several spreading branch roots. Flowers are pale yellow with petals up to 1 inch in length.

It can grow in biomes that range from coniferous forests to piñyon-juniper to grassland. It is a 

very competitive plant – it has been reported to replace spotted knapweed in Montana (Rice,

1991). It is a prolific seed producer, averaging up to 5,600 seeds per plant. Seeds are winddispersed, but typically falling within a foot of the parent plant. Long-distance dispersal can use 

several vectors, as seeds become easily attached to anything passing by. Research indicates seed 

may remain viable in the soil for more than 4 years (Endress & Parks, 2004).

Sulfur cinquefoil is an aggressive invader, causing a decrease in biodiversity of native plant 

communities, and altering natural successional processes. Potentilla recta has been known to 

hybridize with other species of the same genus under natural conditions, thus causing reduced 

reproductive success of native Potentilla species (Endress & Parks, 2004).
Appendix A

30 EA for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest

In northern Arizona, it has been documented along the Rio de Flag and on the Lake Mary Road 

on the Coconino National Forest. It has not been found on the Tonto NF.

Pyracantha 

Pyracantha

Pyracantha is a commonly-used landscaping shrub in the rose family that has small, shiny green 

leaves, spiny stems, and small clusters of white flowers in the spring that mature to red berries. It 

was introduced from China as an ornamental plant. Seeds spread by either water or bird 

distribution.

It is uncommon for this plant to be invasive in the Southwest. There is one site that has been 

identified on the Tonto NF, where plants probably originated from nearby ornamental plantings, 

along Camp Creek at the recreational residences. It was removed by the Cave Creek Complex 

Fire in July 2005; further observations will be made to assess if it will return after being burned.

African sumac 

Rhus lancea

This species is recommended as a low-water use plant for landscaping by the Arizona Department 

of Water Resources website (ADWR, 2004). It has been used extensively in landscaping 

throughout the Phoenix metropolitan area, and is beginning to naturalize in areas with slightly 

higher runoff or greater moisture conditions than the surrounding desert. It may pose a threat to 

native trees in riparian ecosystems in the Sonoran Desert.

It has not been documented on the Tonto NF at the time of this writing.

Russian thistle 

Salsola kali, Salsola tragus

Russian thistle was brought to the U.S. from Russia in flax seed about 100 years ago. It has 

spread rapidly. It is a bushy annual plant, growing to from 1⁄2 foot to 6 feet in height. At maturity, 

the stem breaks off at ground level, giving the plant its most common name, tumbleweed. Seeds 

are dispersed as the plant tumbles across miles of desert. One plant may produce thousands of 

seeds, which remain viable for years.

Russian thistle is a restricted, noxious weed in Arizona. It is a common invader of disturbed 

areas, especially along roadsides. In Arizona it has not been observed moving into undisturbed 

areas. Nitrates produced during periods of rapid growth may be toxic to wildlife and livestock.

It is found on the Tonto NF on recently disturbed soils along roads and highways, and at mining 

and millsites. Experienced natural resource managers at the Arizona Department of 

Transportation state they have not seen this plant spread beyond the immediate area of 

disturbance, where it phases out under competition when native perennial grasses and other native 

plants recover (Horsley, 2004).
Appendix A

EA for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest 31

Mediterranean sage

Salvia aethiopis L.

Mediterranean sage is an erect, coarse biennial or short-lived perennial, with a stout taproot. The 

squarish stem, opposite leaves and bilabiate flowers are typical of the mint family. When crushed, 

a sage-like odor is emitted.

This species is native to Mediterranean North Africa. In Nevada it invades rangelands and 

pastures, but spread to undisturbed areas has been limited.

Mediterranean sage reproduces by seed. Each plant can produce 50 to 100,000 seeds. Each flower 

produces four smooth, egg-shaped seeds. Seeds mature by late August, but they are not usually 

dispersed until September or October, when consistent moisture is available for germination.

Mediterranean sage acts like a tumbleweed to disperse the seeds. The flowering stem has an 

abscission line 4 to 6 inches above the ground. The stem becomes brittle and light, and breaks off 

at this line. These stalks roll with the wind, often ending up in fence lines or creek bottoms. When 

seeds get wet and imbibe water, they produce a mucilaginous cover within 5 minutes to protect 

them from desiccation (WSNWCB, 1999).

Mediterranean grass

Schismus arabicus, S. barbatus

Mediterranean grass is an annual short grass, native to southern Europe, northern Africa and the 

Near East (Jackson, 1985). It was in Arizona before the 1900s, and is now particularly abundant 

where grazing, off-road vehicle use, or construction of linear corridors has reduced vegetative 

cover. Mediterranean grass out-competes the native annual grass, six-weeks fescue, and tends to 

replace it through time (Brooks, undated).

Schismus germinates in early winter, normally 2 weeks after receiving at least 0.4 inches of 

precipitation. It typically matures in March, but can produce seed in as little as two weeks.

Schismus can also germinate after summer rains and can survive for up to four months with no 

additional rains (Gutterman & Evenari, 1994).

It generally occupies the space between shrubs in desert communities, and its extensive shallow 

root system monopolizes precipitation to the exclusion of native annual grasses. Dead stems of 

Schismus remain standing for long after the plant dies, serving to carry fire across inter-shrub 

spaces in normally sparse deserts of Arizona and California.

Wild mustard 

Sinapis arvensis

Wild mustard is a winter annual forb, with bright yellow, four-petalled flowers in small clusters

on thick stalks. The stems are branched near the top and have upper leaves that are toothed and 

lower leaves with deep lobes, both hairy underneath. Mature plants are 0.3 to 1 meter tall. Wild 

mustard is spread by seed. Each plant produces 2,000 to 3,500 seeds that may remain viable in the 

soil for several years. It is commonly a crop weed. It reduces crop yields, lowers crop value, and 

can reduce livestock forage production on pastures. Wild mustard is native to Eurasia.
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32 EA for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest

There are a few small infestations of this mustard growing along Highway 188, from Punkin 

Center to Roosevelt, on private lands. It is very common on the Agua Fria National Monument, 

west of Cave Creek Ranger District’s Perry Mesa tobosa grassland. The combination of drought, 

fires, and grazing may have allowed the infestation on the Monument to increase in recent years 

(Fenner, 2005b).

Saltcedar 

Tamarix parviflora, Tamarix chinensis, T. ramosissima

"There is probably not another genus of plants as well known as the tamarisks in which the 

species are so poorly understood or separated on more obscure characters" (McDaniel & Duncan,

2006). Each species has a distinct distribution in Eurasia, but they may have hybridized in the 

southwestern United States (Smith, et al., 1997). Most saltcedars, or tamarisks, are deciduous 

shrubs or small trees growing to 12 to 15 feet in height and forming dense thickets. Saltcedars are 

characterized by slender branches and gray-green foliage. The bark of young branches is smooth 

and reddish-brown. As the plants age, the bark becomes brownish-purple, ridged and furrowed. 

Leaves are scale-like, about 1/16 inch long and overlap each other along the stem. They are often 

encrusted with salt secretions. From February to November, large numbers of pink to white 

flowers appear in dense masses on 2-inch long spikes at branch tips. Saltcedar spreads 

vegetatively, by adventitious roots or submerged stems, and sexually. Each flower can produce 

thousands of tiny (1/25-inch diameter) seeds that are contained in a small capsule usually capped 

with a tuft of hair that aids in wind dispersal. Seeds can also be dispersed by water. Seedlings 

require extended periods of soil saturation for establishment. The fragile seeds remain viable for 

at most 45 days under ideal conditions (Stevens, 1990).

Saltcedar is found in many riparian areas throughout the West. It was introduced in the early 

1800s as an ornamental and for erosion control.

Saltcedars are fire-adapted species and have long tap roots that allow them to intercept deep water 

tables and interfere with natural aquatic systems. They can also increase the risk of fire in riparian 

ecosystems through deposition of flammable fuels (Brooks & Minnich, 2006).

Saltcedar disrupts the structure and stability of native plant communities and degrades native 

wildlife habitat by out-competing and replacing native plant species, monopolizing limited 

moisture, and increasing the frequency, intensity, and effect of wildfires. The foliage of tamarisk 

can add salt deposits to the soil, inhibiting growth of other species (Egan, et al., 2009; Brotherson 

& Field, 1987). Although it provides some shelter, the foliage and flowers of saltcedar provide 

little food value for native wildlife species that depend on nutrient-rich native plant resources 

(Muzika & Swearingen, 2005b; Brooks & Minnich, 2006).

Saltcedar is able to use salty water. It does this by absorbing the salts through cell membranes. It 

avoids the toxic effects by using special glands to excrete the salts and by dropping salt-filled 

leaves. The leaves dropped each fall accumulate to a considerable depth under the canopy. 

Through this process, saltcedar acts as a salt pump concentrating salts from deep in the ground 

onto the soil surface. Over time, salts in the mulch layer kill existing plants and prevent others, 

especially desirable riparian species, from becoming established. As a result, the ground under a 

saltcedar or within a saltcedar thicket is void of plants except, on occasion, another salt tolerant 

species (Johnson, et al., 2002).
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EA for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest 33

The federally endangered Southwestern willow flycatcher (Empidonax traillii extimus) is known 

to nest in saltcedar thickets. There has been concern that control of saltcedar would present a 

threat to recovery of this subspecies of flycatcher. In fact, this endangered flycatcher prefers to 

feed and breed in riparian woodlands dominated by native plants such as willow, baccharis, and 

arrowweed. In addition, flycatcher nests would be subject to much greater risk of fire in saltcedar 

dominated riparian areas than in riparian areas dominated by native vegetation.

On the Tonto NF, saltcedar grows sparsely in many small drainages and along the Verde River 

and its tributaries. It grows densely along much of the Salt River both above and below the chain 

of lakes. Management of Salt and Verde River reservoirs has created habitat for saltcedar at 

inflows into the reservoirs, where there are deep silt deposits and water levels fluctuate too much 

for native riparian trees such as cottonwood and willow to survive (Fenner, 2005b). Saltcedar is 

able to withstand longer periods of inundation than native riparian trees (Butler, 2002).

Siberian elm

Ulmus pumila

Siberian elm is a fast-growing tree in the elm family (Ulmaceae) distinguished by small-toothed 

leaves about 1 to 21⁄2 in long and half as wide, and pointed at the tip. Mature trees reach a height 

of 50 to 70 feet, with a round crown of slender, spreading branches. The bark is rough, gray or 

brown, and shallowly furrowed at maturity. Flowering occurs in the springtime, either before or 

with bud break for leaves. After flowering, a single seed forms in the center of each smooth, 

flattened, circular, 1⁄2 inch wide fruit. The seeds are easily windborne to distant areas and 

germination rate is high (Wieseler, 2005).

Preferred habitat is dry to mesic open areas and streambanks at high elevations. Once a tree has 

become established, thickets of seedlings form underneath it and in disturbed sites in the vicinity.

Fast growing seedlings easily overtake native vegetation, especially shade-intolerant species. This 

often leads to invasion by additional weedy species (Wieseler, 2005).

This tree was introduced to the U.S. in the 1860s for its cold and drought-hardiness (Wieseler,

2005). It is fairly common in northern Arizona, often planted as a shade tree. There are currently 

isolated infestations on the Coconino National Forest east of Flagstaff, and in the Verde 

River/Lynx Lake/Thumb Butte areas of the Prescott National Forest (USFS, 2004, Feb.).

A small population of Siberian elm was recently documented in the Grapevine Canyon area near 

Camp Creek, on the Cave Creek Ranger District. It was apparently planted by one of the 

recreational residence owners on that drainage, and has produced numerous sprouts after the Cave 

Creek Complex Fire of 2005.

Periwinkle 

Vinca major

Vinca is a spreading perennial vine, introduced from southern Europe and northern Africa as an 

ornamental groundcover and medicinal herb. It spreads vegetatively and is not known to 

reproduce sexually (Bean & Russo, 1986). Plants spread by sprawling stems that root at the 

nodes. It grows best in moist shady environments. 
Appendix A

34 EA for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest

In the U.S., Vinca’s range extends from California throughout the southern states.

Water can spread broken stem fragments along riparian areas, where it can easily sprout and 

spread rapidly. Once established, it forms a dense groundcover that prevents growth and 

establishment of other plant species (Drewitz, 2005). In Ramsey Canyon in southern Arizona, 

Vinca has suppressed natural erosional processes in the creek, promoting deepening and scouring 

of the creek bed and altering local hydrology and vegetation (McKnight, 1993).

Vinca naturalizes from gardens on private lands within or adjacent to the National Forest.

Grantham homestead on Highway 288 is one example. Numerous small patches of Vinca cover 

approximately four acres along Camp Creek and on homeowners’ lots in the recreational 

residence section of Camp Creek Canyon. It occupies sites adjacent to or in the channels of Camp 

Creek, Columbine Creek, and Grapevine Canyon, and also floodplains and dry shady slope sites.

It also grows in the nearby Seven Springs area.