Weed Department
Idaho State Noxious 
Weed Law
Hoary Alyssum


General Description: Hoary alyssum is an upright annual, biennial or short-lived perennial herb growing about 1 to 3.5 feet tall. Plants are covered in stellate hairs causing it to look silvery-gray in color.

Flower Description: Flowers are in simple or branched clusters (racemes) and bloom from the bottom up. Flower petals white, two times longer than sepals and are deeply cleft. Each flower has 6 stamens.

Leaf Description: Plants have basal and stem leaves. Basal leaves are oblanceolate, 0.75 to 2 inches long by 0.2 to 0.4 inches wide, and have smooth margins. Leaves gradually reduce in size moving up the stem with alternate leaf arrangement.

Stem Description: Stems are generally unbranched near base and branched above.

Fruit/Seed Description: Seeds are in somewhat inflated pod-like structures called silicles that are oval shaped and around 0.25 inches long. Seeds are round, brown and have narrowly winged margins.


Interesting Facts:

It is noted to invade pastures, out-compete beneficial plants and quickly spread through stressed areas. It has been noted for animal poisoning and potentially cause death. Livestock are known to become intoxicated after eating green or dried plants.