Identifying characteristics:
The horse chestnut is not a "chestnut" at all, but a relative
of the native Ohio buckeye. The name derives from the dark brown, shiny
seeds, which could resemble the eye of a horse. The prickly, nut-like fruits
are similar to those of the true chestnut (Castanea sp.), which has
simple, alternate leaves. The horse chestnut is our largest non-native,
spring-flowering tree, reaching a height and spread of 50 to 75 feet. A
striking specimen tree, this species has a rounded or oval crown and attractive
foliage. The leaves are palmately-compound,
opposite and deciduous, consisting of 5 to 7 leaflets (usually 7). Each
leaflet is coarsely toothed (with teeth of 2 sizes) and abruptly
tapered at the apex. Leaves are dark green, turning an unimpressive light
yellow or brown in the fall. The showy flowers
are produced after the leaves in May and June in large, upright panicles
about 1 foot long. Each flower is white streaked with red or yellow, with
long, yellow, protruding stamens. The fruit
is a 1- to 3-seeded, capsule, 2 inches in diameter, borne in drooping clusters
and ripening in September and October. The capsule turns from green to brown,
is thick and leathery and bears pointed spines. The nutlike seeds are a
dark, shiny brown with a light spot (hilum) and are poisonous to humans.
The buds are ovoid, varnished with a sticky gum, and bear 4 to 6
pairs of large scales. The terminal bud is 0.5 to 1 inch long. The leaf
scars are large, triangular or shield-shaped, with 3 to 9 bundle scars.
The bark is dark gray to dark
brown, becoming shallowly fissured and scaly. The inner bark is orange-brown.
Similar species:
Ecology:
Distribution: Native to south-west Asia and the Balkan Peninsula,
the horse chestnut was introduced to the US in colonial times and now grows
throughout the country.
Habitat: It is hardy from zone 3 to 7 and grows best in moist,
well-drained soils in full sun or light shade. This species is pH adaptable
and it withstands urban conditions, but cannot withstand extremely dry conditions.
Fungal leaf blotch and physiological leaf scorch are the major problems,
although mulching the root area and planting in a sheltered position away
from hot, dry winds can reduce these problems. This species is also susceptible
to anthracnose of the leaves and terminal shoots, canker of the branches,
and powdery mildew. The wood is weak, often allowing rotting fungus to infect
the tree through wounds from broken branches. Comstock mealybug, aphids,
Japanese beetles, leafhoppers and walnut scale may also be problematic.
Uses:
Wood: The wood is whitish, soft and brittle and not naturally
durable. It is close-grained, easy to work and is often used in Europe for
food containers, kitchen utensils, artificial limbs, toys and small turned
articles.
Wildlife: Squirrels feed on the seeds and deer browse the foliage.
Horticulture: This species was once over-planted in the eastern states because of its showy flowers. An ideal specimen for large, open areas, this species is used for landscaping in parks, campuses and golf-courses. The large size, weak branches and messy fruit, however, make this tree an undesirable choice for the small yard.
