Fauna
Plant

Hoary Alyssum

Berteroa incana

Also known as False Hoary Madwort, Hoary Berteroa, Hoary Alison

Hoary alyssum blankets disturbed pastures, roadsides, and dry fields with clusters of small, deeply cleft white flowers borne atop greyish stems. Covered in dense, star-shaped hairs that give the foliage a frosted, hoary texture, it thrives in dry, sandy soils where native grass cover is sparse. While relatively unpalatable to most livestock, it retains potent toxins when harvested into dry hay, posing serious health risks to horses.

InvasiveWildflowerWhite Bloom
Hoary Alyssum reference1 / 7
(c) Anders Hastings, some rights reserved (CC BY), uploaded by Anders Hastings · cc-by
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Not EvaluatedConservation statusIUCN Red List categoriesLCNTVUENCREWEXNot Evaluated — not placed on the risk ladderRed List categories, explained →
Key facts
Diet & preyAutotrophic (Photosynthetic)
Predators
  • Flea Beetles
  • Grasshoppers
ThreatsHerbicide treatments, mechanical removal, competitive native planting
HabitatsPastures, roadsides, dry grasslands, disturbed sandy soil
Life spanAnnual to short-lived perennial
Classification
  1. OrderBrassicales
  2. FamilyBrassicaceae
  3. GenusBerteroa
  4. SpeciesBerteroa incana
Range & activity
Range data is not available yet.
Safe observation
Interaction riskHigh
  1. Low
  2. Moderate
  3. High
  4. Very high
Why interaction risk is high
Toxic to horses when ingested in pasture or hay; inspect forage carefully.
Why it is dangerous
Ingestion of fresh plants or contaminated hay causes toxicity in horses, inducing lower leg swelling, laminitis, high fevers, and severe stiffness.
How to recognize a risky encounter
Recognize the erect stems covered in fine star-shaped hairs, white four-petaled flowers with deeply notched petals, and flattened oval seed pods.
What to do
Keep horses away from infested pastures and discard baled hay containing this plant; wear gloves when pulling weeds.
Responsible observation
  • Forage Inspection: Examine baled hay closely for greyish stems and small oval seed pods to protect horses.
  • Manual Removal: Pull small patches by hand before seeds mature, taking care to extract the taproot.
  • Soil Cover: Maintain dense perennial grass cover to prevent windblown seeds from colonizing bare earth.
Related species
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