Hoary cress

(Cardaria draba)

Erect, perennial herb up to 0.6 meters (2 feet) tall. Has a flat-topped appearance. Introduced from Eurasia, most likely in contaminated alfalfa seed. Also known as Lepidium draba.

Quick Identification:

• White flowers with 4 petals, approx. 1/4 inch across.
• Dense flower clusters give a flat topped appearance.
• Lower leaves are stalked and hairy while upper leaves clasp the stem and are usually hairless.
• Inflated, upside down, heartshaped seedpods.

Interesting Facts:

Above ground parts are high in vitamin C.

Management:

Mowing 2–3 times a year for several years may slow the spread and reduce seed production. Mowing should be conducted during the bud stage and repeated when the plants re-bud.  Selective herbicides are effective.

Reproduction and Dispersal:

Primarily by rhizomes and root fragments; can form dense patches of clones over an area of 3.6 meters (12 feet). Also reproduces by seed. Can produce two crops of seeds per year.

Habitat Preference:

Meadows, fields, roadsides, ditches, waterways, cultivated lands and rangelands. Particularly adapted to sub-irrigated pastures with alkaline soils.

Flowers:

White flowers with 4 petals, approximately ¼ inch across. These dense flower clusters give the weed a flat-topped appearance early in the season, but this is lost as the stem elongates.

Leaves and Stems:

Leaves on mature plant are shaped like arrowheads, alternately arranged, and have finely toothed edges. Basal rosette has bluish-green, lance shaped leaves. A single stem, often branched near the top, has one flower cluster.

Seeds:

Inflated seedpods are shaped like an upside down heart. Seedpods contain two reddish brown, egg-shaped seeds separated by a narrow partition. Viable up to three years.

Roots:

Rhizomatous, with vigorous creeping root system. Below ground buds develop new shoots. Root system comprises over 75% of the plants total biomass; can grow up to 9 meters (30 feet).

Impacts:

Hoary cress is an early bloomer and can easily create a dense mono culture that out-competes native plants.  It is generally unpalatable to livestock.

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