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FACT SHEET: PERENNIAL PEPPERWEED

Perennial Pepperweed 

Lepidium latifolium L. 

Mustard family (Brassicaceae) 

NATIVE RANGE 

Southeastern Europe and southwestern Asia 

DESCRIPTION 

Perennial pepperweed (synonym: Cardaria latifolia (L.) Spach), is also known 

as tall whitetop, giant whiteweed, perennial peppergrass, slender perennial 

peppercress, broadleaf or broadleaved pepperweed, ironweed and other 

names. Plants are multiple stemmed and grow in stiffly erect masses up to 5 ft. 

(1.5 m.) tall, sometimes taller. Leaves are lanceolate, bright green to gray 

green, and entire or toothed. Basal leaves are stalked, up to 1 ft. (30 cm) long 

and 3 in. (8 cm.) wide and have serrate margins. Stem leaves are smaller, 

ranging from 3-10 in (7-25 cm) in length, tapered at the base, entire to weakly 

serrate and are sessile to stalked. Flowering occurs from early summer to fall. 

Abundant small white 4-petaled flowers are borne in dense clusters near the 

stem tips. The fruits are small, flattened pods about 1/10th inch long, each 

containing 2 seeds (1 per chamber). Fruits remain on the plant, dropping 

irregularly throughout the winter. The base of the stem is semi-woody. The 

roots enlarge at the soil line, forming a woody crown. Root length is dependent on soil tilth, but can be up to 6 feet. Roots 

are creeping, with new plants springing from root sections as small as 2 inches. Seedlings, when present, have leaves 

that are ovate to oblong, 1⁄4-1⁄2 inch long, with smooth to slightly wavy edges and a petiole approximately 1/5th inch long. 

Subsequent leaves resemble first leaves, but are larger in size. 

ECOLOGICAL THREAT 

Perennial pepperweed is a highly invasive herbaceous perennial. It can invade a wide range of habitats including riparian 

areas, wetlands, marshes, and floodplains. It adapts readily to natural and disturbed wetlands. As it establishes and 

expands, the plants create large monospecific stands that displace native plants and animals. It addition to impacting 

alfalfa and pasture production, it has been reported to adversely affect food quality and nesting habitat for native birds and 

threaten the Carson’s Wandering Skipper butterfly. Most of the reports of habitat and food quality are anecdotal. 

DISTRIBUTION IN THE UNITED STATES 

Infestations have been reported in coastal, intermountain and mountainous 

areas in New England, all the states west of the Rocky Mountains, except 

Arizona. It also occurs in Canada and Mexico. 

HABITAT IN THE UNITED STATES 

Perennial pepperweed occurs in riparian (stream) areas, coastal wetlands, 

marshes, roadsides, railways, ditches, hay meadows, pastures, cropland, and 

waste places. 

BACKGROUND 

Pepperweed probably entered the U.S. prior to 1940 in a shipment of beet seed (Beta vulgaris) from Europe. 

BIOLOGY & SPREAD 

Perennial pepperweed rarely produces seedlings in the field. There is no known reason for this, as laboratory tests have 

shown seed viabilities to be high. Seeds lack a hard seed coat and lose viability rapidly, suggesting that resurgence of a 

treated infestation from the seed bank would be low. The plant mainly propagates clonally from its brittle rhizome-like 

roots. Roots exposed by washouts and land disturbances fragment and move along riparian corridors to start new 
7 June 2005 Page 2 of 3 

Plant Conservation Alliance®s Alien Plant Working Group 

Xeeds HoneXild: Alien Plant Invaders of Natural Areas 

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infestations downstream. Roots fragmented by the mechanical actions of land 

management practices increase infestation densities and facilitate spread. 

MANAGEMENT OPTIONS 

Deep-seated rootstocks make pepperweed difficult to control. With the exception of 

continual flooding, no non-chemical treatments have been found to effectively control 

this weed as a sole control option. Excellent control can be obtained with a 

combination of herbicides and cultural practices which fit in various control strategies, 

but application of the control plan must be repeated numerous times to obtain lasting 

management. Slow recovery of desirable plants is often an issue when combating 

pepperweed. Revegetation with desirable species may be necessary to restore the 

landscape. 

Perennial roots can also remain dormant in the soil for several years, thus intense early 

detection monitoring and removal are the best control measures for perennial 

pepperweed. Sources of infestations should also be located and eliminated to prevent future infestations. Treating 

pepperweed with herbicides at a non-optimal time of year (e.g. other than at 

flower bud) is ineffective, as the roots, where carbohydrates are stored, are not 

affected by the spray and new plants will rapidly resprout. 

 The most effective control regimes are: 

• Spring grazing with subsequent chlorsulfuron or imazapyr application 

at flower bud 

• Spring mowing with subsequent chlorsulfuron or imazapyr application 

at flower bud 

• Glyphosate alone at flower bud when populations are not dense 

• Spring mowing followed by glyphosate at bud stage in wetland areas 

Chemical 

Foliar application

Only foliar application methods have been shown to be effective. A list of herbicides, sites where the compound has been 

approved for use, restrictions, and effectiveness is included in the table. For rates and other important information, see the 

herbicide label. 

Herbicide Site Restrictions Effectiveness 

Telar® (chlorsulfuron) Noncrop, Industrial Selective herbicide (will not 

harm most grasses), do not 

apply near water. 

Excellent control for 1-2 years 

Habitat® (imazapyr) 

Stalker® (imazapyr) 

Riparian, Wetlands 

Wildlands 

Nonselective herbicide, do 

not apply near water. 

Excellent control for 1-2 years. 

Treated areas typically remain void of 

any vegetation for 1-2 years after 

treatment. 

Roundup® and others 

(glyphosate) 

Rodeo®, Aquamaster® 

and others (glyphosate) 

Wildlands 

Aquatic 

Nonselective herbicide. 

Rodeo for areas near/in 

aquatic sites. 

Effective unless infestation is dense. 

If dense, mow area and apply to 

resprouting plants. 

Weedar 64® (2,4-D) Wildlands, 

Aquatic 

Selective herbicide (will not 

harm grasses) 

Somewhat effective unless infestation 

is dense. If dense, mow area and 

apply to resprouting plants. 

Manual and Mechanical 

Mechanical control options are typically not effective. Very small patches can be controlled by hand removal if the process 

is repeated often for several years and plants are not allowed to mature. Because root systems are brittle and can extend 

so deep in the soil most mechanical techniques, such as disking, can spread the weed and increase the density. 
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Plant Conservation Alliance®s Alien Plant Working Group 

Xeeds HoneXild: Alien Plant Invaders of Natural Areas 

http://www.nps.gov/plants/alien/

USE PESTICIDES WISELY: Always read the entire pesticide label carefully, follow all mixing and application instructions and wear all 

recommended personal protective gear and clothing. Contact your state department of agriculture for any additional pesticide use 

requirements, restrictions or recommendations. 

NOTICE: mention of pesticide products on this page does not constitute endorsement of any material.

CONTACTS 

For more information on identification and control of Perennial Pepperweed, contact: 

• Debra A. Boelk, University of CA-Davis, Plant Sciences daboelk at ucdavis.edu 

• Joe DiTomaso, University of California-Davis, ditomaso at vegmail.ucdavis.edu 

• Mark Renz, New Mexico State University, markrenz at nmsu.edu 

• University of California- Davis, Agriculture and Natural Resources, Weed Research and Information Center, 

http://wric.ucdavis.edu/ 

• USDA Agricultural Research Service, Exotic and Invasive Weeds Research 

http://www.ars.usda.gov/main/site_main.htm?modecode=53-25-43-00 

OTHER LINKS 

• http://nbii-nin.ciesin.columbia.edu/ipane/icat/browse.do?specieId=8

AUTHOR

Debra A. Boelk, University of California-Davis, Plant Sciences, Davis, CA 

REVIEWER

Joe DiTomaso, Cooperative Extension Specialist, University of California-Davis, Davis, CA 

EDITOR

Jil M. Swearingen, National Park Service, Center for Urban Ecology, Washington DC 

PHOTOGRAPHS 

Joe DiTomaso, Cooperative Extension Specialist, University of California-Davis, Davis, CA 

REFERENCES

Boelk, D.A., DiTomaso, J.M. and Wilson, R.G. Integrated Management of Perennial Pepperweed. Manuscript in 

preparation. 2005. 

Renz, M.J. Element Stewardship Abstract for Lepidium latifolium. TNC library 04 Apr 2000. 21 Mar 2005. 

http://conserveonline.org/2001/05/d/en/lepilat.rtf 

Swearingen, J. 2009. WeedUS Database of Plants Invading Natural Areas in the United States: Perennial Pepperweed 

(Lepidium latifolium). http://www.invasive.org/weedus/subject.html?sub=5931. 

USDA, NRCS. 2009. The PLANTS Database (http://plants.usda.gov). National Plant Data Center, Baton Rouge, LA 

70874-4490 USA. 

Whitson, T. "Weeds of the West" Western Society of Weed Science. 

Young, J.A., Palmquist, D.E. and Wotring, S.O. 1997. The Invasive Nature of Lepidium latifoloium: A Review. pp. 59-65. 

In, Plant Invasions: Studies from North America and Europe. J.H. Brock, M. Wade, P. Pysek, and D. Green, eds. 

Backhyus Publishers, Leiden, The Netherlands. 

Young, J.A., Turner, C.E. and James, L.F. Perennial Pepperweed. Rangelands, 17(4), August 1995.