Family: Sapindaceae, Hippocastanaceae
Species: Aesculus flava
Etymology
Aesculus was the Latin name for an oak or any tree whose seeds could be eaten by livestock, while flava (or flavum) is the Latin word for “yellow,” referring to the yellow flowers of the horse chestnut.
Description
The leaves are palmate, composed of five (rarely seven) leaflets, each 10–25 cm long and wide. They are deciduous and typically turn orange to red in autumn. The flowers grow in a showy raceme, ranging from yellow to yellow-green. Each flower is 2–3 cm long, with stamens that are shorter than the petals. The nectar attracts hummingbirds, bees, butterflies, and other pollinating insects, while the nuts attract squirrels. After flowering, the horse chestnut fruit develops, consisting of 1–2 shiny seeds enclosed in a leathery, light brown skin.
The trunk can vary from dark gray to brown when young and becomes furrowed and rippled in middle age, then scaly and flat when mature. The fruit of the horse chestnut resembles a deer’s eye, hence the name “buckeye.” The wood is soft and has an unpleasant smell when green, but once seasoned, it is odourless, white, and light.
Habitat
The species is native to the Ohio Valley and the Appalachian Mountains of the eastern United States.
Notes and Curiosities
Native Americans, as well as North American Indians, historically obtained food from the seeds of the largest horse chestnuts after roasting and soaking them to remove the toxic element. The seed contains saponins and must be detoxified before consumption. It is said to be bitter, but once cooked, it can become “sweet as a chestnut.”
The flowers of this plant have a distinctive feature: the inner part near the reproductive organs is marked by spots that gradually change from yellow ochre to orange and red. This polychromy is tied to the pollination of the individual flower. If insects have not yet visited the flower, the spot is yellowish. Once pollinated, it changes color from orange to red, signaling to insects that they should move on to another flower that has not yet been fertilised and still offers abundant nectar. Pollinators thus learn that the brighter-coloured flowers have the most food and head toward them with confidence.
A. flava is cultivated as an ornamental tree. Its showy yellow flowers and beautiful autumn coloration make it appealing in large gardens and parks. The tree can grow in almost any soil but requires plenty of space. In the Heller Botanical Garden, we also find, in addition to A. flava, A. parviflora, a graceful shrub with elegant leaves and upright inflorescences made up of panicles of thin white flowers with long, protruding stamens that have very red anthers, as well as splendid autumn foliage.