Stevens County Noxious Weed Control Board
This web site will help you identify & control noxious weeds. Conventional & biological control
(BioControl) information and photographs  are here. Maps & related information are included.

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Hoary Alyssum
Berteroa incana L.                 
Mustard Family

Key identifying traits

  • Flowers are white with 4 petals, deeply divided
  • Usually only branched at the top of the plant
  • Leaves are alternate, blades are simple
  • Fruit is oblong, with two compartments containing 2 to 6 seeds
  • Seeds grow close to stem, are round to oblong, narrowly winged, grayish-brown and rough

Biology and ecology

  • Can be an annual, winter annual, biennial, or a short-lived perennial (!)
  • Most abundant in disturbed sites but is also found in meadows and pastures
  • Starting to be an invader in alfalfa crops
  • 1 to 2 ½ feet tall
  • Can be toxic to horses if it comprises 30% or more of their diet
  • Spreads rapidly due to the high number of seeds per plant; spreads only by seed
  • Likes direct sunlight but can also tolerate shade

Control

Prevention – Learn to identify plants; know your property; beware of fill dirt, hay and seed from outside your area

Biological – No known biological control

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

Mechanical – Hand pulling or digging can be very effective for small infestations but should be done before flowering

Chemical – Several effective at label rates but may require more than one application. If in flower, it’s too late to spray for the year. The PNW Weed Management Handbook does not have this weed listed for control recommendations, but other annual mustard recommendations may be useful


seeds pods & flowers


Hoary alyssum on street corner


Hoary alyssum in tree planting


Hoary alyssum on a mountain road


Where found –
Largest infestations in the county are in Chewelah and Northport areas but Hoary alyssum is spreading rapidly.

MSdoc     PDF

 

weedboard@co.stevens.wa.us
Last Edit: February 25, 2010
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