Hoary Cress
Lepidium draba
Washington State Classification
Class C — Widespread, County-Selected Control
Hoary cress is a highly competitive plant forming a monoculture, and once established, it easily displaces native vegetation.
Quick Reference
Identification
Growth Habit
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.
Leaves
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).
Flowers
Plants have many somewhat flat-topped clusters of white flowers. Each flower has 4 petals and blooms April to July.
Fruit & Seeds
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.
Impact
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.
Ecology & Spread
Habitat
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.
Spread Mechanisms
Reproduction
Hoary cress reproduces from both root fragments and seed.
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Control Methods
Mechanical
- Mechanical removal is strongly discouraged. Small, broken root fragments that are left behind will form a new plant that will produce many more plants.