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Orange Hawkweed

Orange hawkweed (Hieracium aurantiacum), also known as devil’s paintbrush, fox and cubs, king devil,

and missionary weed, is a showy perennial distinguished by bright orange-red flowers that are evident

throughout the summerand early fall. Hawkweed takes its name from the ancient Greek word hierax,

“hawk”, because the Roman naturalist Pliny believed that hawks fed on this plant to strengthen their

eyesight (Nietering 1982).

Originating from Europe, orange hawkweed is recognized as an ecologically invasive plant and noxious

weed in the United States and Canada and is also recorded on Australia’s Alert List of 28 plants that

threaten biodiversity and cause environmental damage. Orange hawkweed was introduced to North America

as an ornamental, desirable for its attractive flame-colored flowers, sometime prior to 1818. Invasive

qualities have allowed this plant to easily escape landscape and garden plantings and it can now be

found in native meadows, forest openings, pastures, roadsides, and right-of-ways from Florida to

Alaska. Once established, it quickly spreads by seed, aboveground stems (stolons), and below ground

stems (rhizomes), developing dense patches that displace native vegetation. 

Orange hawkweed has the potential to seriously degrade many Alaskan ecosystems, particularly riparian

and wildlife areas. It is currently recognized as an invasive weed in south-central and southeast

Alaska, where it was reportedly introduced in the late 1950s in Juneau (Hultén 1968). Planted as a

pretty ornamental, this weed has escaped and become established on many acres of roadside and disturbed

areas and is encroaching into many undisturbed sites across Alaska, including sites in Wrangell and

Petersburg. It has become common in the communities of Homer and Kodiak, and is now invading natural

forb/fern meadows within the Kodiak National Wildlife Refuge. Infestations have also been discovered

around the Anchorage basin and in Girdwood. 
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Description

Orange hawkweed is an upright perennial of the sunflower family that is characterized by a single,

leafless stem (occasionally one or two small leaves may be present on the stem), which is approximately

12 inches tall and covered with stiff black hairs. The oblong or lance-shaped basal leaves are also

hairy, and measure about 41⁄2 inches in length. Both stems and leaves exude a milky sap when broken.

Each stem terminates with a cluster of ray-type flowers that are characteristically red on the margin

merging into an orange center. The bright orange-red flowers, each measuring about 1⁄2 inch in diameter,

are easily distinguished from other flowers by their notch-tipped, square-edged petals (Figure 1).

Each flower produces 12–30 tiny, ribbed, black seeds flattened at one end. Each seed is typified by

minute barbs along each rib that enable them to stick to hair, fur, clothing and vehicles, and a tuft

of bristles on the flattened end. Seeds can be dispersed by wind, water, or “hitch-hiking”, and are

often moved in contaminated soil associated with transplanting new plants into gardens and flowerbeds.

Seeds remain viable in soil for up to 7 years and infested areas often form extensive seed banks.

The roots are shallow and fibrous with aboveground stolons (runners) and below ground rhizomes that

allow for aggressive vegetative reproduction. Stolons originate from buds in the rosette when the

plants flower. These runners radiate out from the original plant and form new rosettes where they touch

down and take root. Under ideal conditions, one orange hawkweed plant can spread and infest an area 2–3

feet in diameter in its first year of growth. Plants regrow each year from the short underground

rhizomes.
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Related Species

Other native and exotic hawkweeds also exist in Alaska; most of these are yellow or white flowered

species (USDA NRCS Plants Database). The natives H. triste and H. gracile are generally found in high

elevation meadows and the native H. albiflorum is found only in the wooded areas near Lynn Canal and

the southern tip of Southeast Alaska (Hultén 1968). The exotic H. murorum is a yellow-flowered species

native to North America but introduced to Alaska where it is spreading in Anchorage and the Matanuska

and Susitna River valleys. Other exotic hawkweeds include H. atratum, H. laevigatum, and H.

caespitosum, which are noxious weeds in several states such as Washington. Hawkweeds are often

difficult to distinguish to the species level and orange hawkweed freely hybridizes with each of these.

However, orange hawkweed is the only species with orange flowers and a typically leafless stem.

Life History

Orange hawkweed usually begins to flower in late May or early June, depending upon the weather. Some

plants may set seed as early as July, but flowering usually lasts through September. Once established,

it rapidly develops into a dense patch that continues to spread by seed, stolons and rhizomes (Figure

2). Each plant produces seed for long-range dispersal and sends out 4–8 stolons for more close-range

reproduction each season.

Orange hawkweed can grow over a wide range of temperature and site conditions. However, plants prefer

full sun or partial shade and soil that is well drained and coarse-textured. Orange hawkweed easily

invades disturbed sites such as those associated with roadsides and residential areas. Infestations of

orange hawkweed can also occur when purchased as a component of commercial wildflower seed mixes or

when propagated by the unwary wildflower enthusiast.

Impacts
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Orange hawkweed is able to form dense mats, which displace native plants and lower biodiversity. With

the ability to reproduce through prolific seed production as well as through vegetative means, orange

hawkweed is an aggressive competitor for space, light and soil nutrients (Figure 3). It has also been

reported to be allelopathic, producing phytotoxic chemicals in its pollen grains that inhibit seed

germination, seedling emergence, or regeneration of other plants (S.D. Murphy 2001).

Guidelines for Control Options

The preferred method for control of orange hawkweed is prevention. To prevent plants from spreading

from existing populations: carefully clean vehicles, boots, clothing, and pets after visiting infested

areas. Seeds are small and easily carried in mud and debris. To prevent new infestations: monitor for

invasive plants, maintain proper turf and ornamental management including watering, fertilizing, and

mowing, and avoid unnecessary site disturbances. Maintain native vegetation that will provide

competition for weedy invaders through appropriate seed mixtures, moderate grazing, fertilization, and

irrigation. Do not use orange hawkweed as a garden ornamental, and review the ingredients of wildflower

mixes to avoid accidental introduction. When possible, avoid using wildflower mixes with unidentified

seed components entirely.

Integrated Pest Management (IPM) practices are recommended for managing populations of invasive plants.

IPM involves a combination of control methods to maximize effective control and minimize negative

environmental impacts.

Small infestations can be controlled through early detection and eradication methods. For control of

small infestations, recommendations include: carefully digging out plants in spring or early summer

when soil is moist, taking care to remove all of the below ground rhizomes and roots (since even a

small piece of overlooked rhizome may develop into a new plant), covering small areas with lightimpenetrable ground covers for several years, or spot treating with an appropriate herbicide, all

followed by reseeding with a suitable grass or grass-forb mixture. If the plants are flowering, make

sure that all plant materials are discarded in a sealed, heavy-duty plastic bag and landfilled.  Any

remaining flower heads should be removed and bagged before seeds mature. Because orange hawkweed is

perennial and reproduces through rhizomes that will resprout from any fragments left in the soil, as

well as stolons, mowing these weeds is not effective. Monitoring of treated areas for missed plants or

regrowth is suggested for several years with continued treatments as needed.

For larger infestations, herbicides may be the only effective control method. For seedling control, the

earlier they can be treated, the better. For established plant control, the vegetative to pre-flowering

stages of plant growth are best, followed by a fall regrowth stage, after the plants have completed

their seed filling for the season and are storing excess food reserves in the rhizomes/roots.

Monitoring of treated areas for plants growing from seed or root fragments should continue for several

years.

Orange hawkweed will quickly reinfest a non-revegetated area following a non-selective herbicide

application, which would kill both orange hawkweed and non-target vegetation. Selective broadleaf

herbicides should be used, which minimize non-target organism control as well as minimize environmental

degradation. Contact your nearest Cooperative Extension Service office for current information on

herbicide recommendations and use. Once areas have been treated, an ongoing commitment is required to

ensure new infestations do not establish. Poorly planned control efforts or lack of monitoring can

actually increase the spread of this weed and worsen the problem. 
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Many invasive weeds, including orange hawkweed, have escaped from gardens. Always obtain correct

species identification prior to planting something new in your garden. The detrimental impacts of these

weeds far outweigh any potential horticultural benefits.  Do not buy seeds via the Internet or mail

order catalogues unless you can be sure they are free of invasive plants such as orange hawkweed. Take

care when traveling to not bring back seeds attached to hiking or camping equipment, and “spread the

word not the weed” (Figure 4).

Caution: Pesticides can be injurious

to humans, domestic animals, desirable plants, and

fish or other

wildlife—if they are not handled or

applied properly. Use all pesticides selectively and

carefully. Since

approved uses of a pesticide may

change frequently, it is important to check the label

for current approved and legal use.

Follow recommended practices for the

disposal

of surplus pesticides and pesticide

containers.

Mention of a pesticide in this

publication does not

constitute a recommendation for use by

the USDA,

nor does it imply registration of a

product under

Federal Insecticide, Fungicide, and

Rodenticide

Act, as amended. Mention of a

proprietary product

does not constitute an endorsement by

the USDA.

References

Niertering, E. 1982. Name dropping Linnaean style. Minnesota Press 1(2).

Hultén, E. 1968. Flora of Alaska and Neighboring Territories: A Manual of the Vascular Plants. Stanford

University Press, Stanford, CA. pp. 958-960.

Murphy, S.D. 2001. The role of pollen allelopathy in weed ecology. Weed Technology 15(4):867-872.

USDA, NRCS. 2004. The PLANTS Database, Version 3.5 (http://plants.usda.gov). National Plant Data Center,

Baton Rouge, LA 70874-4490 USA.

Photography Credits

Cover photo and Figures 1 & 2: M. Shephard, Ecologist, USDA Forest Service, Alaska Region, State and

Private Forestry.

Figure 3: Leslie Kerr, US Fish and Wildlife Service, Refuge Manager, Kodiak National Wildlife Refuge.

Figure 4: J. Snyder, UAF Cooperative Extension Service, Anchorage.
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Orange Hawkweed

Cynthia Snyder and Michael Shephard, USDA Forest Service, Alaska Region, State and Private Forestry.

Additional information on this plant can be obtained from your local USDA/University of AlaskaFairbanks, Cooperative Extension Service office, Alaska State Forestry office, or from:

Forest Health Protection, State & Private Forestry

USDA Forest Service:

3301 “C” Street, Suite 202

Anchorage, Alaska 99503

Phone: (907) 743-9455

2770 Sherwood Lane, Suite 2A

Juneau, Alaska 99801-8545

Phone: (907) 586-8883

DNR Forestry Northern Region Office

3700 Airport Way

Fairbanks, Alaska 99709

Phone: (907) 451-2701

Or:

www.fs.fed.s/r10/spf/fhp/fhpr10.htm

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