Meadow saffron (Colchicum autumnale), often referred to as autumn crocus, is a small herbaceous perennial bulb from the Colchicaceae family. The plant typically blooms in early fall. It produces showy pink, purple to white flowers in groups of 1 to 6 from an underground bulb. In the spring, leaves with fruit emerge and remain through July.
All parts of C. autumnale are toxic to horses, especially the bulb and seeds. The primary toxin is colchicine, a cytotoxic alkaloid that is able to inhibit microtubule formation. The other toxins present which are closely related to colchicine, include: desacetylmethylcolchicine, desacetylthiocolchicine, colchicoside, demethyl desacetylcolchicine.
Consumption of 0.1% of the horse's body weight in leaves can be fatal to an average sized adult horse. C. autumnale is toxic in fresh or dry form, and horses can sometimes accidentally ingest the plant in its dried form from contaminated hay bales. Signs of poisoning typically appear within 2 to 12 hours following ingestion of the plant.