Hoary Cress

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

Hoary Cress


Cardaria spp

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.