Hoary Cress

Cardaria draba - Brassicaceae Family - Rhizomatous perennial

Identification

• Flowers:  White with four petals, giving the plant a flat-topped appearance.
• Seeds:  Heart shaped capsules, each containing two seeds.
• Leaves:  Blue-green and lance shaped with the upper leaves clasping the stem.
• Flowering Time: Pre bud April – May; Flowering May - June.
• Life cycle/ other:  Biennial reproducing by seed and by rhizomes.

Impacts 

• Hoary cress out-competes native plant communities by forming dense monocultures.
• Hoary cress contains glucosinolates that are toxic to livestock at high levels.

Most effective control methods

• Control of hoary cress is very difficult because of an extensive root system that can grow up to 50 new plants from one lateral rhizome.
• The best control method for large infestations is by working from the outside in, controlling the infestation’s perimeter and monitoring for new infestations beyond the containment area.
• For small infestations, the most common form of control is by herbicide, applied in May or June between bud and flowering time.  Effective choices include: 2,4-D (4 and 6EC), Telar 75 (DF), Ally (60 DF), and Escort.  It is imperative to spray before the plants begin to flower.  If applied after flowering, the plants will set viable seed.
• Mowing, grazing, and cultivation when used alone will not provide effective long-term management. 

Control methods and timing

Prevention (Prev) Monitor and destroy new plants before seed production.

Mechanical (Mech) Hand pulling, digging, cutting, mowing and tilling.

Cultural (Cult) Biological control agents, livestock grazing, and revegetation practices.

Chemical (Chem) Selective herbicides based on the plant and the specific location. Check our weed fact sheets for specific control information.

Hoary cress: flowers and foliage

Hoary cress: foliage

Hoary cress: flowers

Hoary cress: infestation

Hoary cress

Hoary cress: infestation

Hoary cress: entire plant including root system

Hoary cress: flowers

• Hoary Cress Fact Sheet

• References

  DiTomaso, J.M., G.B. Kyser et al. (2013). Weed Control in Natural Areas in the Western United States [PDF file]. Weed Research and Information Center, University of California. Retrieved from https://wric.ucdavis.edu/information/natural-areas/wr_C/Cardaria_chalepensis-draba-pubescens.pdf View PDF

  Invasive Species Compendium. (2018, July 15). Lepidium draba (hoary cress). Retrieved from https://www.cabi.org/isc/datasheet/10621

  Montana State University Extension. (2011, May). Biology, Ecology and Management of Whitetop [PDF file]. Retrieved from http://msuextension.org/publications/AgandNaturalResources/EB0138.pdf View PDF

  United States Department of Agriculture. (2014, September). Field Guide for Managing Whitetop in the Southwest [PDF file]. Retrieved from https://www.fs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb5410132.pdf View PDF

  Zouhar, K. (2004). Cardaria spp. Fire Effects Information System. Retrieved from https://www.fs.fed.us/database/feis/plants/forb/carspp3/all.html