The only species of maple that has been shown to be toxic to horses in the eastern states is the red maple (Acer rubrum). “Autumn Blaze” is a hybrid between red maple (Acer rubrum) and the silver maple (Acer saccharinum). When eaten by horses, the wilted leaves of the red maple can lead to a severe and possibly fatal anemia. Since Autumn Blaze is a hybrid of the red maple, it is possible, although undocumented, that it may be toxic …