Hoary Allysum?

Thanks for the heads up, and this should help raise awareness of all plants poisonous to horses. Your local conservation or extension agency can give out pamphlets with pictures of plants to look for in your area, though you may need to ask your vet for the names of the plants first. I think a lot of people put horses on pasture with no idea that just because it is green, it might not be safe to eat!