Field pepperweed (Lepidium campestre) is a winter or sometimes summer annual weed of reduced-tillage agricultural crops, orchards, and nurseries. While it is often seen in fall seeded alfalfa the following spring, small populations are well managed by hay cutting. It is identifiable by its “bottle-brush” appearance and leaves that clasp the stem.
Field pepperweed infestation
Photo by Steve Dewey of Utah State University via Bugwood.org
Field pepperweed is one of 3000+ species in the mustard family. For help identifying weedy mustards either in the rosette or flowering phase, please visit our mustard identification page.
Identification
Seedlings: Cotyledons of field pepperweed are hairless and club-shaped to oval. They are petiolated and can be up to 15 mm (⅗ ‘’) long. Early leaves are rounded to ovate, alternate, and form a basal rosette on long petioles. Leaves taper towards the base and are rounded at the tip, with wavy toothed to deeply lobed margins.
Field pepperweed seedling
Photo by Joseph M. DiTomaso of University of California, Davis via Bugwood.org
Leaves: Mature field pepperweed leaves are densely covered in short hairs. Stem leaves towards the bottom and basal leaves are oblong with rounded tips and taper towards the base. Its margins are lobed, toothed, or simple. Stem leaves in the upper portion of the plant are arrowhead-shaped and alternate with margins that are simple to partially toothed. They are 2-4 cm (up to 1.5’’) long and clasp the stem. The stems, like the leaves, are densely covered in short hairs.
Mature field pepperweed leaves and stem
Photo by Joseph M. DiTomaso of University of California, Davis via Bugwood.org
Field pepperweed basal rosette
Photo by Joseph M. DiTomaso of University of California, Davis via Bugwood.org
Mature plant: The flower-producing stems, like the leaves, are densely covered in short hairs. They are erect, branched in the upper portion, and can reach up to 3/5 m (2 ft) tall. Basal rosette leaves are present even when the plant is flowering.
Field pepperweed stem
Photo by Mary Ellen Harte via Bugwood.org
Mature field pepperweed leaves and flowers
Photo by Steve Dewey of Utah State University via Bugwood.org
Flowers/Fruit: Flowers emerge mainly in May or June, although they sporadically show in September. They develop in dense racemes on stalks that are up to 8 mm (3/10‘’) long. The flowers are composed of 4 white or greenish petals which are 2-2.5 mm (up to 1/10’’) long, and 6 stamens.
The fruit is oblong to egg-shaped and 5-6 mm (~⅕’’) long by 4 mm (~⅕’’) wide. At the apex there are wing-like structures. The seed is oval, brown, and 2-2.5 mm (~1/10’’) long.
Field pepperweed flowers
Photo by Mary Ellen Harte via Bugwood.org
Field pepperweed fruit
Photo by Joseph M. DiTomaso of University of California- Davis via Bugwood.org
Management
Chemical control
New York specific guidance can be found in the Cornell Crop and Pest Management Guides, or click below for chemical control suggestions for field pepperweed from Cornell’s turfgrass and weed weed identification app.
There are no recorded instances of field pepperweed developing herbicide resistance, but the related and similar Virginia pepperweed (Lepidium virginicum) is also in New York, and has developed resistance to Group 22 (paraquat) in Ontario, CA.
Non-chemical management
Field pepperweed is a typical winter annual that can be managed with a normal weed management routine. The ideal time to deal with winter annual weeds is from late March to early April. Field pepperweed is easiest to manage when the plants are in the rosette stage and have not yet flowered.
Species Similar to Field Pepperweed
Table 1: Shows field pepperweed (Lepidium virginicum) similarities and differences in identification compared to its similar species .| Species | Similarities | Differences |
|---|---|---|
| Virginia pepperweed (Lepidium campestre) | white to greenish flowers in groups of 4 petals, alternate leaves, simple to partially toothed leaf margins | hairy leaves, leaves do not clasp the stem |
| Field pennycress (Thlaspi arvense) | white to greenish flowers in clusters, erect flower stem, narrow leaves which taper at the end | hairless leaves |
References
Uva R H, Neal J C, DiTomaso J M. 1997. Weeds of the Northeast. Book published by Cornell University, Ithaca NY. The go-to for weed ID in the Northeast; look for a new edition sometime in 2019.
Cornell University’s Turfgrass and Landscape Weed ID app. Identification and control options for weeds common to turf, agriculture, and gardens in New York; uses a very simple decision tree to identify your weed.
University of Missouri’s Division of Plant Sciences profile on field pepperweed. Basic identification information for field pepperweed.
University of Massachusetts at Amherst’s profile on field pepperweed. Identification notes on field pepperweed.
Montana State’s Official webpage on field pepperweed. Classification and general description on field pepperweed.
University of Wisconsin-Madison’s Consortium of Wisconsin Herbaria featuring profile on field pepperweed. Physical traits of field pepperweed.
University of Nebraska-Lincoln’s Institute of Agriculture and Natural Resources’ page on Controlling Winter Annual Weeds. Lays out the problems with winter annual weeds and some information on how to control them.