Hoary Alyssum

Hoary Alyssum

Fact Sheet


Latin Name: Berteroa incana

Origin: Eurasia

Physical Description: It is an annual, biennial or short-lived perennial herb with a slender taproot. Its branched stems can grow up to 1.1m tall and are covered in star-shaped hairs. The greenish-grey leaves are lance shaped, alternate along the stem and decrease in size upwards on the stem.  Each flower has 4 deeply notched white petals. Seed pods are flattened and oval shaped and held close to the stem.

Habitat: It prefers sunny locations with dry, gravelly or sandy, nutrient poor soils. It is generally found in waste sites, roadside ditches, pastures, meadows, and rangelands.

Impacts: It can outcompete desirable plants and impact biodiversity and available forage for wildlife and livestock. Hoary alyssum can contaminate hay and reduce hay quality and value. The plant is toxic to horses both fresh and in cured hay, typically with hay comprised of 30% to 70% of hoary alyssum. Affected horses exhibit swelling of the legs, depression and diarrhea.

Reproduction:  It reproduces only by seed. A single plant can produces up to 2640 seeds a year.

Management Options

Mechanical: Small populations can be controlled by repeated hand-pulling or digging as long as the root crown is removed to prevent regrowth.  Mowing can help reduce the seed production but plants typically start growing prostrate to the ground, where the mower blade can no longer reach it.

Chemical: Several herbicides with the following active ingredients can control Hoary Alyssum: Aminopyralid + Metsulfuron methyl, Chlorsulfuron, Metsulfuron, Sulfometuron.  For available products, contact your local agri-supply store. Prior to any herbicide application, read and follow the label instructions.

Biological: None available.

Additional Resources: 

Invasives Species Council of BC’s Hoary Alyssum Factsheet

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