Hoary Cress

Lepidium draba

Hoary Cress

Family: Brassicaceae

Other Scientific Names:

Cardaria draba

Other Common Names: whitetop
Weed class: C
Year Listed: 1988
Native to: Europe, Asia and Northern Africa
Is this Weed Toxic?:

humans, livestock; plants may cause digestive tract irritation.

Why Is It a Noxious Weed?

Hoary cress is a highly competitive plant forming a monoculture, and once established, it easily displaces native vegetation. It has the potential to reduce the value of high-price wheat lands.

How would I identify it?

General Description

It is a rhizomatous perennial that generally grows up to around 2 feet tall, sometimes 3 feet tall. Plants generally covered in short hairs but can be hairless.

Flower Description

Plants have many somewhat flat-topped clusters of white flowers. Each flower has 4 petals and blooms April to July.

Leaf description

Leaves are alternately arranged on the stem, blue-green and lance shaped.  Lower leaves have stalks while upper leaves are without stalks and have two lobes clasping the stem. Leaf margins are irregularly toothed to smooth (entire).

Stem description

Stems are upright to somewhat trailing on the ground. Stems with a lot of branching near the top.

Fruit Seed Description

Seed pods (silicles) are inflated and generally rounded to somewhat heart-shaped (especially at the base) and hairless. Seeds are dark brown and 0.08 inches (2 mm) long. One mature plant can produce 1,200 to 4,800 seeds.

May Be Confused With

Hoary cress is similar to hairy whitetop, Lepidium appelianum, another Class C noxious weed. See more images here. 

Where does it grow?

It commonly grows in disturbed sites, pastures, roadsides, saline soils, and along river banks and other waterways. Please click here to see a county level distribution map of hoary cress in Washington.

How Does it Reproduce?

Hoary cress reproduces from both root fragments and seed.

How Do I Control It?

Mechanical Control

Mechanical removal is strongly discouraged. Small, broken root fragments that are left behind will form a new plant that will produce many more plants.

Herbicide Control

Please refer to the PNW Weed Management Handbook, or contact your county noxious weed coordinator.

For More Information

See our Written Findings for more information about hoary cress (Cardaria draba).

Report on hoary cress from the book "Weed Control in Natural Areas in the Western United States"

Hoary cress (Lepidium draba), also known as whitetop, information from the USDA Forest Service "Field Guide for Managing Whitetop in the Southwest"

Additional images of hoary cress from eastern Washington

Spokane County NWCB Fact Sheet on hoary cress

Douglas County NWCB Fact Sheet on hoary cress

Lincoln County NWCB Fact Sheet on hoary cress

San Juan County NWCB hoary cress poster

Additional Photos