Hippocastanaceae

Hippocastanaceae is a small family of flowering plants that has historically been recognized as a distinct family but is now commonly treated as a subfamily (Hippocantoideae) within Sapindaceae. The group is essentially monogeneric, comprising the genus Aesculus, known as the horse-chestnuts or buckeyes. There are about 15 species of deciduous trees and shrubs native to the temperate regions of the Northern Hemisphere, with widespread horticultural use.

Plants in this group are typically medium to large trees with rough bark and palmate leaves containing five to seven leaflets. In spring they produce upright or branched inflorescences of showy flowers, usually white or pale pink. The fruit is a spiny capsule that splits to reveal a single large, glossy seed, commonly referred to as a conker or horse chestnut.

Aesculus species are valued for ornamental use in parks and streets and have been cultivated widely beyond their native ranges. The seeds and other plant parts contain toxins, and raw seeds are poisonous if ingested. In herbal medicine, extracts from horse-chestnut seeds, notably escin (aescin), have been used to treat venous insufficiency and related conditions, though such preparations should be used under medical supervision due to potential adverse effects.

Notes on classification: In many contemporary systems, Aesculus is placed in Sapindaceae, and Hippocastanaceae is not recognized as a separate family; the traditional name Hippocastanaceae may still appear in older literature. The genus remains the central representative of the group in botanical references.