Perennial Pepperweed

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Perennial Pepperweed (Lepidium Latifolium) is a B-rated weed of limited distribution in Fresno County. It is a perennial herbaceous plant that grows to 1 to 5 feet tall. Pepperweed forms a deep-seated rootstock making the plant difficult to control. The root system can become extensive with depths greater than 10 feet. It will reproduce by seed and root fragments. In the early spring, the plant emerges from the roots as a rosette. Flowering occurs early summer to fall. Pepperweed forms dense clusters of white flowers near the ends of branches. Each flower produces a seed capsule containing two seeds. The seeds are believed to be short-lived and do not germinate well.

Perennial Pepperweed Flower ClusterInfestation in Sierra Mountains East of Clovis
Perennial Pepperweed Flower Cluster (Left), and an Infestation in Sierra Mountains East of Clovis (Right)

Infestations Along RoadsidesSpread Into Adjacent Cropland
Infestations Along Roadsides (Left) Can Spread Into Adjacent Cropland (Right) Greatly Reducing Crop Production

Perennial pepperweed is a non-native invasive noxious weed species that is native to southeastern Europe to southwestern Asia. The first recorded detection in California was in 1936 in Stanislaus County. It is fairly well established in northern California, and spotty throughout the rest of the state. Pepperweed can survive at elevations over 9,000 feet. Contaminated hay or straw bales are believed to be the source of recent infestations. Plowing or discing only breaks up the root and increases the number of plants. Perennial pepperweed will infest waste lands, ditches, roadsides, pastures, meadows, roadsides, and wet areas. If perennial pepperweed has infested a stream bank or canal fragmented roots can float downstream to establish new infestations. This invasive weed can readily overtake and transform a native plant community. It can choke out native plants and trees and render crop land useless.

Each year, during March, the Fresno County Department of Agriculture staff will begin noxious weed surveys for perennial pepperweed and hoary cress, a B-rated noxious weed of limited distribution in Fresno County. Known infestations are west of Firebaugh, around Mendota, north of Helm, east of Clovis and in the Shaver Lake area. Staff will survey and treat as needed.