Aesculus hippocastanum, the horse chestnut,

"Aesculus hippocastanum" is a species of flowering plant in the maple, soapberry and lychee family Sapindaceae. It is a large, deciduous, synoecious tree. It is also called horse-chestnut, European horsechestnut, buckeye, and conker tree. It is not to be confused with the sweet chestnut or Spanish chestnut, "Castanea sativa", which is a tree in another family, Fagaceae.