Hoary Cress

hoary cress seedpod
hoary cress habit
hoary cress flower
hoary cress by creek
hoary cress plant

Hoary Cress

Lepidium draba (formerly Cardaria draba)

Information Sheet (PDF)


Colorado List B - Control required in Jefferson County


General

  • Family: Mustard Brassicaceae
  • Found in moist and transitional areas along right-of-ways, fields and cropland
  • Introduced in late 19th century from Europe


Common Names

  • Whitetop


Habitat

  • Alkaline and disturbed soils
  • Creeping perennial
  • Easily displaces native vegetation
  • Forms monoculture
  • Mature plants grow up to 2 feet tall
  • Very competitive once established


Plant


Vegetation

  • Leaves are blue-green
  • Leaves are often covered with very fine, white hairs
  • Oval or oblong with toothed or almost smooth margins
  • Upper leaves have two lobes that clasp the stem


Roots

  • Deep-rooted, creeping perennial
  • Hoary cress roots release chemicals that hinder growth of cereals
  • Rhizomatous lateral roots send up shoots that develop independent taproots


Flower

  • Color: typically white, four petals
  • Multiple flowers clustered at the end of stems
  • Season: late April and May
  • Size: 1/8 inch across


Seed

  • Heart-shaped seed pod contains two oval, finely pitted, red-brown seeds each about 1/2 inch long
  • Mature plant produces 1,200 to 4,800 seeds
  • Seeds are viable for 1 to 2 years


Seedling

  • Most emerge in April, some fall germination possible under optimum conditions


Reproduction

  • Seed and vegetative means


Control


Biological

  • None


Chemical


Cultural

  • Cultivation  - Spreads the plant and is not recommended unless the area  is plowed every couple weeks during the growing season for up to three  years
  • Hand pulling - Is only minimally effective because the plants regenerate from the roots
  • Prevention – maintain health of site


Mechanical

  • Burning - Not effective
  • Grazing - Not recommended; not readily grazed by livestock. May poison livestock; may taint meat and milk
  • Mowing - Not recommended; may spread seed. May disturb root system; new plants form off of the plant fragments


Use all chemicals according to the manufacturer's label. No specific recommendation or endorsement is made or implied by listing methods or products.

Treatment Timeline


JanFebMarAprMayJuneJulyAugSeptOctNovDec
Control











RemovalNot recommended.  Plants regrow from root fragments
Herbicide











Growth











Vegetative











Flowering











Seed