Horsechestnut
Marronnier d'Inde
Aesculus hippocastanum L.Sapindaceae (soapberry family)Origin: Europe
Origin: Europe
Horsechestnuts are medium to large trees with a broad, rounded crown of arching branches.
Read more about Tree, Bark, Twigs
Erect candle-like clusters of white flowers are borne at the tips of branches in late spring.
Read more about Flowers
Horsechestnuts are medium to large trees, up to 25 m (82') tall and to 150 cm (5') in diameter.
The dense crown is formed by branches that grow upwards, then arc downward before curving up again at the tips.
Young trees have smooth, light grey bark.
Bark on mature trees is dark grey with scaly patches that expose the orange-brown inner bark.
Twigs are greyish-brown, smooth with distinct pores (lenticels) and large leaf scars. Twigs emit an unpleasant odour when bruised.
Terminal buds are large, 2 - 4 cm (3/4"-1.5") long, dark brown and sticky. They stand out especially in late winter.
Leaf scars are large with bundle scars arranged in a U or horseshoe.
Leaves are palmately compound with 5 - 9 leaflets that fan out from the leaf stalk.
Leaflets are 10 - 25 cm (4" - 10") long, broadest above the middle with an abruptly-pointed tip, a tapered base, and coarsely toothed margins.
Leaves have an opposite arrangement on the branch. Newly emerging leaflets droop like an umbrella before they expand.
Leaves turn yellow in the fall.
Flowers are borne in erect clusters, 20 - 30 cm (8" - 12") long, at the tips of branches.
Individual flowers are 2 - 3 cm (about 1") long, tubular with 4 - 5 petal lobes that curve backward, exposing long, protruding stamens.
Petals are white or cream-coloured with red or yellow spots.
Flowers emerge in late spring after the tree is in full leaf.
Fruits are round, 5 - 6 cm (about 2") across, with spiny husks.
Fruits begin to develop from the flowers in early summer.
In the Fall when ripe, the outer husk splits into sections, releasing 1 to 2 nut like seeds.
The smooth, shiny brown seeds are up to 5 cm (2") across, and have a rough whitish patch at one end.
The spreading chestnut-tree in Henry Wadsworth Longfellow's poem, The Village Blacksmith, was a horsechestnut on Brattle Street in Cambridge, Massachusetts.
Distribution
Horsechestnut is native to the Balkan region of eastern Europe and was introduced to central Europe in the 16th century.
Derivation of names
The genus name, Aesculus, is the classical Latin name for an oak with edible acorns, The name derives from esca, the Latin word for food. The species name, hippocastanum, means horse chestnut, from the Greek words hippos, horse, and kastanon, chestnut. The species and common names likely refer to the fact that horsechestnut fruit are somewhat similar to chestnut fruit - a shiny brown nut inside a prickly husk - and that horsechestnuts were fed to sickly horses.
Human use
Horsechestnut seeds are used in a traditional English children's game called conkers (see conkers in Wikipedia) in which the seeds (or conkers) are swung on strings and struck together as each player attempts to break the other's conker.
Because of the inclusion of chestnut in the common name, horsechestnut seeds are sometimes confused with those of sweet chestnuts (Castanea spp) which are edible. In fact, horsechestnuts are poisonous, their seeds, leaves, and bark containing the toxic alkaloid aesculin. Humans should not eat horsechestnut seeds even though the squirrels do. Horsechestnuts have leathery husks with sparse, thorn-like spines and a large pale patch on the round seed. In contrast, sweet chestnut fruits are covered with dense prickly spines, and the nuts are conical, tapering to a point.
Similar species
Horsechestnut is closely related to the native Ohio buckeye (Aesculus glabra), which differs in having leaflets that are widest at the middle, smaller clusters of yellow or greenish yellow flowers, and smaller, non-sticky terminal buds.
Cultivars and hybrids
Several cultivated varieties and hybrids exist, including red horsechestnut (Aesculus x carnea), a cross between horsechestnut and red buckeye (Aesculus pavia), which is native to the southeastern United States.
Horsechestnut's place in Toronto's urban forest
Horsechestnuts were first brought to Toronto in the early 1800s by settlers seeking to recreate the gardens of their homeland. In 1859, five hundred horsechestnut trees were planted on what are now University Avenue, College and Carleton Streets, in preparation for the ceremonial opening of Queen's Park and Allan Gardens by Edward, the Prince of Wales on September 11, 1860. Some of the horsechestnuts planted in Queen's Park at that time may still stand there today.
Landscape value and potential for home planting
Horsechestnut is a popular urban-tolerant ornamental tree that can live more than 100 years. Its large canopy requires considerable space, so it should only be planted in open, sunny sites. Very dry sites should be avoided; it is adaptable to different soil pH levels.
Pests and diseases: Horsechestnut is susceptible to many of the same pests and diseases that affect Ohio buckeye, including leaf blotch (discolored leaf spots that turn brown), Japanese beetle, and flat-headed borer. Leaf scorch, which occurs in dry conditions, causes the leaf margins to curl and turn brown. Branches tend to be susceptible to breakage in high winds.
This tree is available for planting through the City of Toronto's street tree program.
Find trees on Tree Tour maps at Canadian Tree Tours: