Hoary Cress

Hoary Cress

Lepidium draba (formerly Cardaria draba)

Information Sheet (pdf)

Eradication Zone Map (pdf)

Colorado List B - Eradication required in areas of 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

• View Information Sheet (PDF)

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.