Azalea, Rhododendron- Grow in milder climates. Produce variuos cardiac effects if eaten.
Fox Glove- Many varieties throughout the country. Cardiac effects.
Milkweed- Found throughou the US. Very unpalatable but very toxic. Causes sudden death from cardiac arrest.
Kleingrass- Perennial found in Southwestern pastures and hayfields. Toxic in less mature form in early cutting days. Causes liver damage, colic, and photosensitization.
Buckeye and Horsechestnut
Choke Cherry- Found throughout the US. Unusual growing conditions will increase toxicity. Produces cyanide when several parts of the plant are chewed together. Cyanide prevents the uptake of oxygen by the tissues. Death occurs within a few minutes, due to respiratory arrest.
Oleander- Found in milder climates. More palatable when wilted or dired, so horses may readily eat the clippings. Usually fatal because of cardiac effects. May also cause profuse diarrhea and sweating.
Caley Pea- Found in California hays. Toxicity only from ingestion of the seedpod for weeks to months. Horses seem to be in pain and carries itself hunched up, with much of it's weight on the forequarters. Later, rear limb gait abnormalties similar to stringhalt may develop, but pain resoves. Changes could be permanent.
Christmas Plant (Poinsettia)
Hoary Assylum- Found in the Northern half of the US. Frequent contamination of alfalfa and other hays, especially in poor growing seasons. Swelling of the limbs develop within a few days of ingestin. Horses recover when sourse of toxin is removed.
Yellow & White Sweetclover
Red Maple- Problems well documented in the Red Maple, but occur in all maple trees. Ingestion of wilted leaves in the fall from downed branches causes toxic signs. The toxin produced causes a serious change in the chemistry of the blood. May lead to liver or kidney damage or to sudden death.
Bracken Fern- Found in the Northwestern and Northern US to the upper Mid West. Still toxic when baled in hay. Ingestion neccessary for 1 to 2 months, before signs become visible: incoordination, staggering, severe muscle tremors, and wide rear stance. Lowers blood thiamine levels. Threatmeant with Thiamine may reverse symptoms if caught early enough.
Green False Hellebore
Locoweed- Found throughout Western and Central US. Toxic at any time but requires weeks for ingestion. Horses become unpredictable, uncoordinated, has vision disturbances, may have trouble eating, maybe be alternately depressed and excited.
Star of Bethlehem
Black Walnut- Problems occur when horses are bedded on black walnut shavings. Signs are laminitis, swelling of the lower limbs, and depression. Recovery is quick after the shavings are removed.
Black Locust- Tree found in the South Eastern United States. Very toxic when bark is striped and eaten. Signs include weakness, rear paralysis, colic, and depression. Can be fatal.
Black Nightshade- Found south of the Rocky Mountains. Entire plant toxic, especially the berries. Signs include weakness, depression, colic, and profuse diarrhea. Supportive care is very important.
Fiddle Neck- Common weed native to the Pacific Coast states. Several weeks of ingestion can cause liver damage. Signs sre related to those of liver disease and incluse weight loss, lack of appetite, depressin, uncoordination, colic, and swelling. Prognosis for recovery is poor.