Stevens County Noxious Weed Control Board
This web site will help you identify & control noxious weed with information and photographs to aid you.

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Hoary cress & Hairy whitetop
Cardaria draba (L) Desv & Cardaria pubescens (C.A. Mey.)
Mustard Family

Hoary cress & Hairy whitetop are closely related species of mustards. All identifying traits apply to both, unless stated otherwise.

Key identifying traits

  • Flowers are small & white and form dense flat-topped clusters from May to early June
  • Alternate, oblong to arrow-headed leaves clasp the stem; they range from ¾-3" long, have a bluish-green color and a waxy feel to them
  • Fruit is heart-shaped (hoary c.) or globe-shaped (hairy w.) and tipped with a "beak"
  • Seeds are oval and reddish-brown and come two per pod (hoary c.) or four per pod (hairy w.)

Biology and ecology

  • Long-lived perennials, reproducing by seed and underground horizontal roots (rhizomes)
  • Introduced from central Europe & western Asia
  • Will form a large dense spreading colonies if not controlled
  • Thrive under a wide variety of soil conditions
  • Bloom and set seed early in the growing season
  • Problem in ditches, crops and pasture, once established it is very difficult to eradicate

Control

Prevention – Learn to identify plants; know your property; target small infestations aggressively

Biological – No known biological agents yet

Cultural – Good vegetative cover helps but does not prevent establishment or spread

Mechanical – Cutting/tilling will not achieve control due to the underground root system

Chemical – Several effective at label rates but may require repeat treatments to kill root systems; best before bloom or in the fall; refer to the PNW Weed Management Handbook for specific chemical recommendations


rosettes


pods of hairy whitetop


pods of hoary cress

 


infestation


Where found –
Found in scattered locations throughout Stevens County, especially in abandoned crop land.

MSdoc     pdf

 

weedboard@co.stevens.wa.us
Last Edit: March 25, 2015
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