The leaves of Aesculus hippocastanum are opposite and palmately compound with 5 or more leaflets. The only other tree of that description in Wisconsin is Aesculus glabra. The buds of A. hippocastanum are conspicuously sticky and those of A. glabra are not, the flowers are white as opposed to yellow in A. glabra and the leaflets are conspicuously different in shape. The fruits in both species are large spiny, green capsules, each containing 1 or more large shiny, brown seeds.

Aesculus hippocastanum is not native in the U.S.A., but it is widely planted and is quite hardy in cultivation. There appear to be no documented instances of growth outside of cultivation in Wisconsin, but I have seen seedlings on disturbed sites near planted trees in the City of Green Bay and in Door County. One such seedling immediately adjacent to my garage grew to be about 15 feet tall and would presumably have matured if it had not been removed. The seeds have been reported to be poisonous and clearly are unpalatable to squirrels who sample many, but eat none beyond the first tentative bite.