Hoary alyssum (Berteroa incana
) is a biennial or short lived, upright perennial weed that grows 1 to 3 feet in height. It has grayish-green stems that have tiny hairs. B. incana
leaves are gray-green, hairy, oblong, and alternate along the stem. It's flowers appear as small white notched petals, blooming from early spring to late fall. B. incana
seedpods are hairy and oblong with short beaks on the end. It's seeds can germinate while the plant is in bloom.
Contamination of more than 30% or more of hay with B. incana
is toxic to horses, causing clinical signs of lameness, limb edema, haemolysis, hypovolemic shock, and laminitis. The severity depends on the amount of B. incana
consumed and on the horse, as just under 50% of horses ingesting B. incana
show clinical signs. It usually takes 12 to 24 hours following ingestion of B. incana
for the horse to begin to show signs of toxicity.
seedlings which are late to establish themselves will remain as rosettes and produce flowers and seeds the following year, reproducing as winter annuals or biennials. Sometimes B. incana
can form a seed bank which causes seeds to remain dormant for up to nine years. B. incana
seeds are a frequent contaminate of forage and lawn seed, as well as contaminated hay.