Hoary Alyssum

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 there are seed pods. Mowing is not a good control option; plants tend to start growing flat along the ground. Chemical – Several effective at label rates but may require more than one application. If in flower, it can still be effectively controlled with appropriate herbicides. The PNW Weed Management Handbook does not have this weed listed for control recommendations, but other annual mustard recommendations may be useful. Telar and Escort are effective on most mustards and adding 2,4-D can help stop seed viability when plants are in bloom
	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 Colville, Arden, Chewelah and Northport areas but Hoary alyssum is spreading rapidly. MSdoc PDF