Acer spp.



Maple trees can reach heights of up to 100 feet. The red maple (Acer rubrum), often planted as an ornamental, is a beautiful tree with red flowers borne in the spring, before the leaves. Its three to five lobed leaves are 2 to 6 inches long and opposite each other on the stem, bright green above and whitish beneath. Maples provide splendid fall color as the leaves turn shades of yellow through orange or red.


Maple trees may be found throughout the entire eastern half of the United States and Canada, including all regions of Texas.

Toxic Agent

The toxic agent of maple has not been identified. All species of maple should be considered potentially toxic to horses. Feeding studies have confirmed the toxicity of red maple. Most of the intoxications reported have dealt with red maple, but field cases are also reported involving consumption of silver maple with similar clinical signs. Poisoning occurs when horses consume wilted or dry leaves equivalent to 1.5 to 3.0 grams of dry leaves per kilogram of body weight, or about 2 pounds of dry leaves for a 1,000-pound horse. Fresh green leaves are not toxic. Some animals have been poisoned after consuming bark; poisoning usually follows windstorms after which downed trees and limbs become available to the horses. Most cases of maple intoxication occur during the late spring, summer or early fall.

Signs of Livestock Ingestion

Horses consuming maple may have hemolytic anemia and usually show clinical signs within 12 to 48 hours. The most prominent signs are: Yellow or brown mucous membranes; Depression; Anorexia; Weakness; Red or brown urine.

Fatally affected horses usually die within 7 days. Sick animals may have a Heinz body anemia for 2 to 3 weeks before recovery.

Management Strategies

Never place limbs trimmed from maple trees in an area accessible to horses. Check horse pastures or paddocks containing maples for downed branches after a windstorm. Remove any damaged maple before it can be consumed.