Taxonomy

Kingdom: Plantae
Subkingdom: Tracheobionta
Superdivision: Spermatophyta
Division: Magnoliophyta
Class: Magnoliopsida
Subclass: Rosidae
Order: Sapindales
Family: Hippocastanaceae
Genus: Aesculus
Species: indica

The Indian horse chestnut is one of Kew Gardens' Heritage trees. Unlike the other Heritage trees which mainly date from the 18th Century, the Indian horse chestnut was planted as recently as 1935. It was selected by Sidney Pearce (from whence it gets its name), the then Assistant Curator. It was probably a seedling from the Aesculus collection next to the Orangery and is a very strong, broad specimen, producing a large quantity of inflorescence, or flowers. It can be found adjacent to the Nash Conservatory, close to the Main Gate. There are, strangely, three older trees here, supported by three newer plantings.

This tree can grow to 30m in height and 12m in spread. It was introduced into Britain in 1851 from the Himalayas. It is very similar to the horse chestnut  – Aesculus hippocastanum – except for the smooth grey-green bark, the seeds or conkers that are wrinkled, smaller and darker, and it is late flowering. The leaves start out in spring with a bronze colour, becoming a bright glossy green before turning a dark green in summer then an orangey-yellow in autumn. They have five to nine long finger-like leaflets, not dissimilar to the sweet chestnut - Castanea sativa. The Indian horse chestnut flowers around six weeks after other Aesculus species, which makes it very popular with both bees and gardeners alike.

The seeds or conkers of all trees in the Aesculus genus contain a form of saponin called Aesculin. Like all saponins this is potentially toxic, as it destroys red blood cells (erythrocytes). However it is used in the cosmetics industry a great deal, particularly in shampoo and foam bath products. When extracted and dried, it is also a good acidity indicator, fluorescing blue in an acidic pH under ultraviolet light.