Hoary Cress

Family: Brassicaceae

Other common names: whitetop

Weed Class: C

Year Listed: 1988

Native to: Europe, Asia and Northern Africa

Toxic: humans, livestock; plants may cause digestive tract irritation.

additional photos

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:

How does it reproduce?

Hoary cress reproduces from both root fragments and seed.
 

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 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

Additional Photos

Hoary cress infestation

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