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Perennial Pepperweed
WEED ALERT

perennial pepperweed

Threat to Rangeland and Riparian Areas

Perennial Pepperweed
Lepidium latifolium

Family: Mustard

Other Names: Tall whitetop

Description: 
 White-flowered perennial mustard species spreading by seeds and extensive, deep creeping root system. Native to Europe and western Asia.

Stems:
1 to 3 feet tall but can reach 6 to 8 feet in wet areas

Leaves:
 Bright green to gray-green; toothed or entire margins; covered with a waxy layer. 
Lance shaped lower leaves are long-stalked and up to 12 inches long; upper leaves are reduced in size and are either short-stalked or stalkless. 
Distinctive leaf midveins are white.

Flowers:
 White flowers (4 petals), less than 1/8 inch wide, are borne in dense, rounded clusters at branch tips.

Seeds:
 2 reddish-brown seeds are contained in each tiny rounded and somewhat hairy fruit (silicle).

Waxy leaves with prominant white mid-veins
New shoots form along the creeping rootstock
Typical roadside infestation

Concern

The first known B.C. infestation was found in the East Kootenay region north of Cranbrook in 1997. Subsequent infestations were found west of Kamloops near Walachin in 1998. Perennial pepperweed has spread rapidly in northern Europe, Mexico and all western U.S. states, except Arizona.  It invades cropland, roadsides and idle areas but is a particular threat to riparian areas and rangelands. Much of the U.S. infestation is associated with river systems and wetland areas. The extensive, woody, deep creeping root systems makes perennial pepperweed exceptionally difficult to control.

Agricultural producers, range and riparian area managers and the public are requested to be on the lookout for this devastating plant and to take immediate corrective action if the weed is found or suspected.

Damage Caused

Perennial pepperweed is well adapted to a wide range of conditions from the lower edge of coniferous forests to dry sagebrush and alkaline areas. Once established it forms dense, competitive monocultures. Infestations degrade wildlife habitat, lower the yield and quality of forage on pastures and hayfields and destroy biodiversity by interfering with regeneration of native plant species.

What Can You Do?

Prevention to reduce the chances of introduction into a clean field or riparian area should receive the highest priority.
  • learn to identify perennial pepperweed or take suspect plants to the Ministry of Agriculture and Food to confirm identification.
  • Take immediate action by grubbing out, using herbicide treatments or cutting to prevent plants from setting seed.
  • if flowering has occurred, cut and bag plants for burning or deep burial.
  • thoroughly clean equipment, vehicles and footwear before leaving infested sites.
  • Do not move infested soil.
  • Do not Hesitate. Control infested patches immediately.

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