common pepperweed Lepidium densiflorum - University of Alaska

common pepperweed 

Lepidium densiflorum var. densiflorum Schrad. 

tall pepperweed 

Lepidium densiflorum var. elongatum (Rydb.) Thellung. 

Introduction 

Two poorly differentiated varieties of Lepidium densiflorum are recorded in Alaska: common pepperweed (Lepidium 

densiflorum var. densiflorum) and tall pepperweed (Lepidium densiflorum var. elongatum). Both are considered 

together here as common pepperweed (Lepidium densiflorum). 

Synonyms for Lepidium densiflorum var. densiflorum Schrad.: L. densiflorum var. typicum Thellung, L. neglectum 

Thellung, L. texanum Buckl. 

Other common name: common peppergrass, miner’s pepperwort 

Synonyms for L. densiflorum var. elongatum (Rydb.) Thellung.: Lepidium elongatum Rydb. 

Other common names: none 

Family: Brassicaceae 

Invasiveness Rank: 25 The invasiveness rank is calculated based on a species’ ecological impacts, biological 

attributes, distribution, and response to control measures. The ranks are scaled from 0 to 100, with 0 representing a 

plant that poses no threat to native ecosystems and 100 representing a plant that poses a major threat to native 

ecosystems. 

Description 

Common pepperweed is an annual herb that grows up to 

46 cm tall from a slender taproot. Stems are erect and 

branched above with fine, simple hairs. Basal leaves are 

arranged in rosettes. They are stalked, 2 ½ to 10 cm 

long, and usually toothed to deeply lobed. Stem leaves 

are alternate with smooth margins and no stalks. 

Flowers grow on elongate racemes. They are small and 

inconspicuous. Each flower is composed of four green 

sepals and lacks petals. Fruits are flattened, round to 

heart-shaped, small, up to 3 mm long, and slightly 

notched at the tip with papery margins. Each fruit 

contains two seeds (Douglas et al. 1998, Royer and 

Dickinson 1999). 

Similar species: Gardencress pepperweed (L. sativum) 

can be distinguished from common pepperweed by the 

presence of narrowly dissected leaves, reddish-white 

petals, and fruits that are over 6 mm long (Douglas et al. 

1998, Royer and Dickinson 1999). 

Foliage of Lepidium densiflorum Schrad. Photo by M. Harte. 

Fruits of Lepidium densiflorum Schrad. Photo by M. Harte. 

Last Updated: 2011-02-07 by Helen Klein 

http://aknhp.uaa.alaska.edu

Ecological Impact 

Impact on community composition, structure, and 

interactions: Common pepperweed establishes in open 

disturbed sites in Alaska (UAM 2003, AKEPIC 2010). 

No impacts on native populations have been 

documented. 

Impact on ecosystem processes: Common pepperweed 

has little or no effect on natural ecosystem processes 

(Densmore et al. 2001). 

Biology and Invasive Potential 

Reproductive potential: Common pepperweed 

reproduces by seeds only. Each plant can produce up to 

5,000 seeds (Royer and Dickinson 1999). 

Role of disturbance in establishment: Infestations of 

common pepperweed are usually associated with 

anthropogenic disturbances. Plants may appear on sites 

of previous human use, particularly when the soil is 

disturbed by construction or trampling (Densmore et al. 

2001). 

Potential for long-distance dispersal: At maturity, stems 

can break off from the bases and tumble in the wind, 

spreading seeds (Rutledge and McLendon 1996). 

Potential to be spread by human activity: Common 

pepperweed is a weed of cultivated crops and can be 

spread as a contaminant in commercial seed (USDA 

2010). 

Germination requirements: Common pepperweed 

requires disturbance and open soil to germinate 

(Densmore et al. 2001). 

Growth requirements: Common pepperweed grows best 

in light, sandy soils (Rutledge and McLendon 1996). 

Congeneric weeds: Field pepperweed (Lepidium 

campestre), perennial pepperweed (L. latifolium), 

clasping pepperweed (L. perfoliatum), and roadside 

pepperweed (L. ruderale) are known to occur as nonnative 

weeds in North America (Royer and Dickinson 

1999, USDA 2010). Perennial pepperweed is considered 

a noxious weed in British Columbia and 13 states of the 

U.S. (Invaders 2010). 

Legal Listings 

Has not been declared noxious 

Listed noxious in Alaska 

Listed noxious by other states 

Federal noxious weed 

Listed noxious in Canada or other countries 

Distribution and abundance 

Common pepperweed grows in disturbed areas, 

roadsides, waste areas, farmyards, and cultivated fields 

(Welsh 1974, Royer and Dickinson 1999). 

Native and current distribution: Common pepperweed 

is native to North America, but may have been 

introduced recently into Alaska and Yukon (Hultén 

1968, Cody 2000). Common pepperweed grows in 

Canada, the U.S., and Europe (Hultén 1968). This 

species has been documented from the Pacific Maritime 

and Interior-Boreal ecogeographic regions of Alaska 

(Hultén 1968, UAM 2003, AKEPIC 2010). 

Pacific Maritime 

Interior-Boreal 

Arctic-Alpine 

Collection Site 

Distribution of common pepperweed in Alaska 

Management 

Common pepperweed can be controlled easily by hand 

pulling or herbicide applications. Due to the large, longlived 

seed banks, several treatments may be necessary to 

completely remove populations (Densmore et al. 2001). 

References: 

AKEPIC database. Alaska Exotic Plant Information 

Clearinghouse Database. 2010. Available: 

http://akweeds.uaa.alaska.edu/ 

Cody, W.J. 2000. Flora of the Yukon Territory. Ottawa: 

NRC Research Press; 669 p. 

Densmore, R. V., P. C. McKee, C. Roland. 2001. Exotic 

plants in Alaskan National Park Units. Report 

on file with the National Park Service – Alaska 

Region, Anchorage, Alaska. 143 pp. 

Douglas, G. W., G. B. Straley, D. Meidinger, J. Pojar. 

1998. Illustrated flora of British Columbia. V. 

2. Ministry of Environment, Lands and Parks 

Ministry of Forests. British Columbia. 401 pp. 

Hultén, E. 1968. Flora of Alaska and Neighboring 

Territories. Stanford University Press, Stanford, 

CA. 1008 p. 

Invaders Database System. 2010. University of 

Montana. Missoula, MT. 

http://invader.dbs.umt.edu/ 

Royer, F., and R. Dickinson. 1999. Weeds of the 

Northern U.S. and Canada. The University of 

Alberta press. 434 pp. 

Rutledge, C.R., and T. McLendon. 1996. An 

Assessment of Exotic Plant Species of Rocky 

Mountain National Park. Department of 

Rangeland Ecosystem Science, Colorado State 



University. 97 pp. Northern Prairie Wildlife 

Research Center Home Page. 

http://www.npwrc.usgs.gov/resource/plants/exp 

lant/index.htm (Version 15DEC98). 

UAM. 2003. University of Alaska Museum. University 

of Alaska Fairbanks. http://hispida.museum.uaf. 

edu:8080/home.cfm 

USDA. 2010. The PLANTS Database. National Plant 

Data Center, Natural Resources Conservation 

Service, United States Department of 

Agriculture. Baton Rouge, LA. 

http://plants.usda.gov 

Welsh, S. L. 1974. Anderson’s flora of Alaska and 

adjacent parts of Canada. Brigham University 

Press. 724 pp.

common pepperweed Lepidium densiflorum - University of Alaska

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