Hoary Alyssum (Cluster) (Berteroa incana) is a pale, gray-green flowering plant that forms dense groupings of upright, wiry stems topped with small white flowers. Its leaves and stems are covered in fine, silvery hairs that give the plant a hoary, or frosted, appearance. Also known simply as Hoary Alyssum, this Eurasian native has become a widespread invasive weed across North America, especially in dry, disturbed soils, roadsides, pastures, and gravelly areas.

In clustered growth, it forms weedy mats that quickly dominate open spaces, reducing native plant diversity. Its flowers bloom in loose clusters, often creating a haze of white across affected landscapes. Though small and somewhat delicate in appearance, the plant is highly resilient and toxic to horses, making it a concern in rangeland management. Its aggressive seed spread and drought tolerance contribute to its success as both a flowering and colonizing invasive weed, especially in clustered infestations.