Hoary Cress (Lepidium draba)
Keys to ID:
- White flowers.
- Erect growth to 10 to 24" tall.
- Leaf is 3/4" to 4" long with blunt end and fine white hairs.
Identification:
- Lifecycle: Perennial
- Growth form: Forb
- Flower: Numerous white flowers with four petals giving plant a white, flat-topped appearance. Flowers May thru June
- Seeds/Fruit: Seed capsules are heart-shaped and contain two reddish-brown seeds. Germinates in the fall.
- Leaves: Alternate, blue-green, and lance-shaped. Lower leaves are stalked, while the upper leaves have two lobes clasping stem.
- Stems: Mature plant has erect stems reaching 2 feet tall.
- Roots: Rhizomatous; 29 to 32” deep. (Belliston et al. 2004).
- Propagation: Seeds germinate in the fall; overwinters as rosettes. Also spreads by rhizomes.
Control:
Mech: Because of the extensive root system, removing new shoots is extremely important. Where physical conditions permit, hoeing or tilling at intervals of 3 to 4 weeks may be effective. Soils must remain moist between hoeing so that plants can regenerate and deplete their root reserves. Plants must be completely removed within 10 days after emergence throughout the growing season for 2 to 4 years (USFS 2006). Mowing several times before the plants bolt stresses it and allows for better chemical efficacy.
Cautions:
Some people are allergic to hoary cress and have respiratory symptoms when exposed to flowering plants.
Synonyms:
Whitetop