Perennial Pepperweed

• Native to Asia, Europe and Northern Africa.
• This plant is also on the Washington State quarantine list. It is prohibited to transport, buy, sell, offer for sale, or distribute plants or plant parts of quarantined species into or within the state of Washington or to sell, offer for sale, or distribute seed packets of seed, flower seed blends, or wildflower mixes of quarantined species into or within the state of Washington.

• Normally grows 1 to 3 feet tall but may reach up to 6 feet.
• Flowers are milky white and are formed into dense rounded clusters at the branch tips. They have 4 sepals and 4 petals.
• Leaves are alternate, waxy, and have smooth or toothed margins. They have a prominent whitish midvein.
• Multiple stems emerge from a woody base.
• 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.

Photos: WA State Noxious Weed Control Board

• Perennial Pepperweed is 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.

• 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.

• 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.
• Planting competitive vegetation aids in control.

• The best way to control this weed is by applying effective, systemic herbicides. Most other methods of management do not give long-term control.

• aminocyclopyrachlor + chlorsulfuron (Perspective)
  • Rate 1.8 to 3.2 oz/a aminocyclopyrachlor + 0.7 to 1.3 oz/a chlorsulfuron (4.5 to 8 oz/a of product)
  • Apply to actively growing plants in spring
  • Adjuvants can be used; these include methylated seed oils 0.5 to 1% v/v, nonionic surfactants at 0.25 to 1% v/v, and crop oil concentrates at 1% v/v. Can be applied using an invert emulsion rather than water
  • Even low rates can kill nontarget tree and shrub species so avoid application within a distance equal to the tree height of the sensitive species. Do not allow spray to drift off target. Can injure several grass species including bromes, as well as basin wildrye.

• chlorsulfuron (Telar)
  • Rate 0.75 oz ai/a (1 oz/a)
  • Apply in fall or in spring up through bloom stage.
  • Adding surfactant and/or 2,4-D improves control.
  • Do not let spray drift onto sensitive crops. Labeled for use on pasture, range, Conservation Reserve Program (CRP), and non-cropland only.2,4-D amine

• imazapic (Plateau)
  • Rate 0.125 to 0.188 lb ai/a
  • Apply after blossoms open (full bloom) until plants desiccate. Fall rosettes also may be treated if moisture permits.
  • Lightly cover foliage with spray solution. Add 1 quart/a methylated seed oil.
  • Before using, note crop rotation restrictions.

• metsulfuron (Escort)
  • Rate Escort: 0.6 to 1.2 oz ai/a (1 to 2 oz/a)
  • Apply to actively growing perennial pepperweed.
  • Selective to grasses. Use a surfactant.
  • Do not allow spray to drift onto sensitive crops. Apply only to non-crop sites.

• 2,4-D amine
  • • Rate 4 lb ae/a.
    • Apply at the bud stage of growth.
    • Repeat treatments if needed. Good grass cover helps control.
    • Avoid drift to sensitive crops.