Perennial Pepperweed
Lepidium latifolium
Washington State Classification
Class B — Control Required (Designated)
It forms dense infestations that can turn into monocultures.
Required control in Region 1 (all western Washington counties)
Quick Reference
Identification
Growth Habit
Perennial pepperweed normally grows 1 to 3 feet tall but may reach up to 6 feet.
Leaves
Leaves are alternate, waxy, and have smooth or toothed margins. They have a prominent whitish midvein.
Flowers
Flowers are milky white and are formed into dense rounded clusters at the branch tips. They have 4 sepals and 4 petals.
Fruit & Seeds
Rounded to egg-shaped silicles (seed pods) form that are compressed and 0.09 inches (2.4 mm) long. Silicles with stigma present at tip.
Impact
It forms dense infestations that can turn into monocultures. Accumulations of its semi-woody stems degrade nesting habitat for wildlife. It can also displace more desirable species which poses a particular threat to natural areas and hay meadows.
Ecology & Spread
Habitat
Perennial pepperweed may be found in a variety of places: waste areas, wet areas, ditches, roadsides, cropland and in dry habitats. In coastal areas, the plant invades brackish marshes. Please click here to see a county level distribution map of perennial pepperweed in Washington.
Spread Mechanisms
Reproduction
It reproduces by seed, rhizomes and root fragments. It produces abundant seed with a high germination rate. Large populations more commonly expand by creeping rhizomes, which may advance 3 to 6 feet from the parent plant.
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Control Methods
Mechanical
- Mechanical control of this plant is very difficult because very small sections of root contain buds that will sprout into new plants. Plant tops are easily killed, but root and crown buds can sprout and continue the infestation. Small infestations may be hand-pulled or dug, but as much of the root must be removed as possible.
Biological Control
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