Scientific name: Aesculus hippocastanum
Plant type: Deciduous tree
Bloom: Long, pyramidal inflorescence with white flowers
Environment: Full sun to part shade in well-drained soil
Uses: Landscape or specimen tree
Aesculus hippocastanum L. is a large tree with showy inflorescences native to the Balkans. An exceedingly popular ornamental, A. hippocastanum, or horse-chestnut, is widely grown in temperate regions around the world.
For many years, the tree’s native range was unknown, with many different locations suggested, ranging from Asia to North America. Today, we know that A. hippocastanum can be found growing in the wild throughout the Balkan region of southeastern Europe and northwestern Asia. In this native range, Aesculus hippocastanum is considered to be Vulnerable by the IUCN Red List. The vulnerability of these populations is due in large part to the infestations of the leaf miner moth Cameraria ohridella, a fragmented wild population, and deforestation.
The horse-chestnut has a long history in western horticulture and was first introduced to Europe in the sixteenth century and the United States in the mid eighteenth century. The tree quickly became quite popular and was planted widely across cities in Europe. The species was particularly popular in Bavaria, Germany where it was used to aid in storage for biergartens and breweries. Breweries would keep ingredients in underground storage, and needing a constant temperature, planted horse-chestnut trees to provide shade that would keep these spaces cool. A. hippocastanum was chosen largely because it is one of the first trees to produce leaves in the region as temperatures begin to rise in the late Spring.
In the wild, the horse-chestnut can grow to heights of over 100 ft. It has palmately compound leaves, meaning that multiple leaflets radiate from a central point similar to the palm of a hand. In the early Spring, A. hippocastanum produces large inflorescences comprised of white flowers tinged with yellows to reds at the base of the petals, that are quite popular with bees. The tree produces spiny fruits that enclose a deep, shiny brown nut. This nut was thought to help coughing horses when eaten, giving the tree its common name. And though well known, these raw nuts are harmful to humans if ingested. They are, however, quite popular with children in Great Britain and Ireland for the game known as conkers.
Text by Victoria Stewart. Photos by Victoria Stewart and David Kruse-Pickler.