Perennial pepperweed

Lepidium latifolium · Aquatic plants

Whole plant · Photo: Don Loarie / CC BY

InvasiveShoreline

Also called Giant whitetop, Tall whitetop, Broadleaved pepperweed

State noxious weed listing

Idaho: Containment
Oregon: B list (T)
Wyoming: State designated noxious weed

How to identify Perennial pepperweed

Many stems 2 to 5 feet tall from a woody crown
Lance shaped, waxy, blue green leaves
Dense, rounded clusters of tiny white four petaled flowers in June and July
Old tan stems stay standing through winter

Similar plants

Whitetop (hoary cress) is under 2 feet tall with arrow shaped leaves that clasp the stem and flowers in flat topped clusters in spring.

Growth profile

Growing season	Rosettes appear in early spring, stems bolt in May, flowers June and July, seeds by late summer, and dead stems persist.
Starts growing	Early spring
Light	Full sun to part shade
Depth	Moist banks and seasonally flooded ground
How it spreads	Creeping roots that resprout from small pieces, and seeds
Habitat	River and canal banks, pond and reservoir shores, wet meadows, flood plains and salty or alkaline soils.

Why it matters in a lake

Forms dense stands that push out native shoreline plants and wildlife habitat and pull salts to the soil surface. Root pieces resprout, so mowing, tilling and pulling tend to spread it.