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Hoary cress
  • Perennial herb up to 0.6 meters tall

  • Introduced from Eurasia

  • Also known as Lepidium draba

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Hoary cress
(Cardaria draba)

Quick Identification

  • White flowers with 4 petals about 6 mm 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, heart-shaped seedpods

Impact
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.

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.

Flower
White flowers with 4 petals, approximately 6 mm 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 & 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.

Hoary cress

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.

Reproduction & Dispersal
Primarily by rhizomes and root fragments; can form dense patches of clones over an area of 3.6 m. Also reproduces by seed. Can produce two crops of seeds per year.

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.

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

Interesting Facts
Above ground parts are high in vitamin C.

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