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Class B Noxious Weed

Perennial Pepperweed
Lepidium latifolium
 

Perennial pepperweed flower

Other common names: Whitetop, Perennial peppercress, broadleafed pepperweed
 Plant family: Brassicaceae
Year listed: 1999
Native to: Southern Europe, Western Asia

Why is it a noxious weed?

An aggressive plant, perennial pepperweed tends to establish and rapidly colonize  pastures, riparian habitats, and waste places in wetter areas. The plant can also be a problem in roadside, rangeland, and field crop situations. It often reaches fields via irrigation ditches from riparian areas. Dense infestations of the plant can form near monocultures. Accumulations of perennial pepperweed’s semi-woody stems degrade nesting habitat for wildlife. The extremely competitive plant may also completely displace more desirable species, which poses a particular threat to natural areas and hay meadows.

How would I identify it?
General Description: Perennial pepperweed normally grows 1 to 3 feet tall, but may reach up
to 6 feet.

Leaves:

  • alternate
  • waxy
  • smooth or toothed margins
  • prominent whitish midvein

Flowers:

  • milky white
  • formed in dense rounded clusters at branch tips
  • 4 sepals and 4 petals

Stems:

  • multiple stems
  • emerge from a woody base

Line drawings are taken from 1,000 Weeds of North America, copyright of XID Service, Inc and used with permission. Permission granted by the author.

How does it reproduce?
Perennial pepperweed reproduces by seed or rhizome. It produces abundant seed, which has a high germination rate.  Large populations more commonly expand by creeping rhizomes, which may advance 3 to 6 feet from the parent plant. Perennial pepperweed can also reproduce by root fragments

Where does it grow?

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.

What is the distribution in Washington State?

 

 

 

Click on map to enlarge.
  • Perennial pepperweed has been documented mainly in the eastern region of Washington, although it has been documented in portions of western Washington as well. Refer to map for distribution levels in specific counties.
  • If you think you may have seen this weed, please contact your county weed coordinator or us at noxiousweeds@agr.wa.gov.

 

  • Distribution map is based on 2003 data.

How do I control it?

General control methods:

Cultural:  Planting competitive vegetation aids in controlling perennial pepperweed. Small infestations may be hand-pulled or dug, but as much of the root must be removed as possible.

Herbicide: Please refer to the PNW Weed Management Handbook, or contact your county noxious weed coordinator.

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.
 

Biological: None known.

For more information
For more information, download our Written Findings.

 

More Photos-Click photo to enlarge
Feel free to download, or contact us to receive high-resolution JPEG or TIFF formats

Close up of Perennial pepperweed flower.

 Last updated September 10, 2008