also see the not closely related but similar sweet chestnut
Aesculus hippocastanum is a large deciduous, synoecious tree, commonly known as horse-chestnut or conker tree.
Aesculus hippocastanum is native to a small area in the Pindus Mountains mixed forests and Balkan mixed forests of South East Europe. It is widely cultivated in streets and parks throughout the temperate world, and has been particularly successful in London parks and gardens.
AE. HIPPOCASTANUM.—The Common Horse Chestnut. Asia, 1629. A fine hardy free-flowering tree, supposed to have been introduced from Asia, and of which there are several varieties, including a double-flowered, a variegated, and several lobed and cut-leaved forms. The tree needs no description, the spikes of pinky-white flowers, which are produced in great abundance, and ample foliage rendering it one of, if not the handsomest tree of our acquaintance. It gives a pleasing shade, and forms an imposing and picturesque object in the landscape, especially where the conditions of soil—a rich free loam—are provided. Ae. Hippocastanum alba flore-pleno (the double white Horse Chestnut), has a decidedly pyramidal habit of growth, and the flowers, which are larger than those of the species, are perfectly double. It is a very distinct and desirable large growing tree. Ae. Hippocastanum laciniata and Ae. Hippocastanum digitalis are valuable for their divided leaves; while Ae. Hippocastanum foliis variegatis has the foliage rather irregularly variegated.
the flower and leaves of the common horse chestnut
Edward Step has this to say about the Horse Chestnut in his Wayside and Woodland Trees.
Horse Chestnut (Æsculus hippocastanum).
Our placing the Chestnut and the Horse Chestnut into juxtaposition must not be understood as a recognition of any relationship that may be implied in their names, but rather the reverse—to accentuate the differences that exist between them, and which have led botanists to separate them widely in all systems of classification. Although the fruits are sufficiently similar to have suggested the name Chestnut being applied to this, with a qualifying prefix, they have been produced by flowers of entirely different character. Evelyn tells us that the word Horse was added because of its virtues in “curing horses broken-winded and other cattle of coughs,” a statement for which he was no doubt indebted to Parkinson (1640), who says, “Horse Chestnuts are given in the East Country, and so through all Turkie, unto Horses to cure them of the cough, shortnesse of winde, and such other diseases;” but seeing that, in this country at least, horses refuse to touch them, there can be little doubt that the name was given to indicate their inferiority to the Sweet Chestnut, and by a process only too well known to the student of early botanical literature, the name was afterwards held to be proof of their medicinal value to horses.
The Horse Chestnut is a native of the mountain regions of Greece, Persia, and Northern India, and is believed to have been introduced to Britain about 1550. It is not a tree that will be found in the woodlands, or even by the wayside, except when it is behind a fence; yet it constantly greets the rambler who has left the suburban gardens behind him, and in the public parks—notably the magnificent avenue of Bushey Park—where by contrast it exhibits itself as the grandest of all flowering trees. Though the stout cylindrical bole is short, its erect trunk towers to a height of eighty or a hundred feet, supporting the massive pyramid, beautiful on account of its fine foliage and handsome flowers alike. The stout branches take an upward direction at first, then stretch outward and curve downwards, though in winter, when relieved of the weight of foliage, their extremities curl sharply upward, and the great buds in spring are almost erect.
These brown buds, with their numerous wraps and liberal coating of varnish, afford considerable interest to the suburban dweller in early spring. He watches their gradual swelling, and the polish that comes upon them through the daily melting of their varnish under the influence of sunshine. Then the outer scales fall flat, the upper parts show green and loose; there is a perceptible lengthening of the shoot, which leaves a space between those outer wraps and the folded leaves. Next the leaflets separate and assume a horizontal position as they expand. Then probably there comes a frost, and next morning the leaflets are all hanging down, almost blackened, flaccid and dejected-looking. A warm southerly rain, followed by sunshine, reinvigorates them, and we see that the lengthening of the shoot has actually brought the incipient flower-spike clear into view. By about the second week in May the pyramid is clothed with bold handsome foliage, against which the conical spikes of white blossoms, tinged with crimson and dotted with yellow, stand out conspicuously.
The leaves are almost circular, but broken up, finger-fashion, into seven toothed leaflets of different sizes, which appear to have started as ovals, but the necessity for not overcrowding their neighbours has necessitated the portion nearest the leaf-stalk taking a wedge shape. The large size of these leaves—as much as eighteen inches across—leads the non-botanical to regard the leaflets as being full leaves. On emerging from the bud the leaves are seen to be covered with down, but as they expand this is thrown off.
Horse Chestnut. A, flower; B, fruit.
The flowers consist of a bell-shaped calyx with five lobes, supporting five separate petals, pure white in colour, but splashed and dotted with crimson and yellow towards the base of the upper ones, to indicate the way to the honey-glands. There are seven curved stamens, and in their midst[Pg 142] a longer curved style proceeding from a roundish ovary with three cells. In each cell there are two seed-eggs, but as a rule only one egg in two of the cells develops into a “nut.” The ovary develops into a large fleshy bur, with short stout spines, which splits into three valves when the dark-red glossy seeds are ripe. In the Sweet Chestnut the brown skin of the nut is the ovary, which had been overgrown by the prickly involucre; here the spiny green shell is the ovary, and the “nut” a seed. Though horses will not eat this bitter fruit, cattle, deer, and sheep are fond of it. Pounded in water, it becomes one of the numerous vegetable substitutes for soap. Under the name of Konker, or Conqueror, it affords a seasonal joy to the average boy, who first bombards the tree with sticks and stones to dislodge the fruit, and then threads the ruddy konkers on string and does battle with a chum similarly equipped, the one whose string is broken or pulled from his hand by the conflict of weapons being the vanquished. In some parts the game is led off by the recitation of the rhyme, “Oblionker! my fust konker.”
Fruits of Horse Chestnut.
Bole of Horse Chestnut.
The growth of the tree is very rapid, and consequently the timber is soft and of no value where durability is required. Still, its even grain and susceptibility to a high polish make it useful for indoor wood, such as cabinet-making and flooring. It is also used for making charcoal for the gunpowder mills. Although Salvator Rosa and other landscape painters have made such good use of the Sweet Chestnut pictorially, they have utterly neglected the Horse Chestnut; and Hamerton hints that the cause of this neglect is the artist’s inability to represent its large flowers and leaves by the landscape painter’s ordinary method of laying on masses of colour: this requires drawing. The tree begins to produce fruit about its twentieth year, and continues to do so nearly every year. Its age is estimated as about two hundred years. The bark, at first smooth, breaks into irregular scales and in old trees a twist may be developed, as illustrated by our photo of the bole.
The generic name Æsculus (from Latin esca, food) has no real connection with the tree, the ancients having given it to some species of Oak with edible acorns (vide Pliny), but by some unknown means it has become transferred to a tree whose fruit is far too bitter to be eaten by man.
The Red-flowered Horse Chestnut (Æsculus carnea) is a smaller and less vigorous tree. Its origin is unknown, but it is believed to be a garden hybrid that made its appearance about 1820.