In one respect the horse chestnut (Æsculus hippocastanum) may be reckoned among the most remarkable trees of British woodland, inasmuch as, although it has been found in a wild state only here and there among the mountains of Greece and Albania, where it enjoys a climate widely dissimilar from that of Western Europe, it has a constitution so cosmopolitan as to become thoroughly at home in all parts of our country. It thrives as vigorously on the dry chalk soil of Hertfordshire as on the soaked hillsides of Perthshire, and, given reasonable shelter from violent winds, produces its magnificent foliage and flowers as freely near sea level as it does at Invercauld in Aberdeenshire, where there is, or was not long ago, a fair specimen growing at an elevation of 1,110 feet, not far short of the practical limit of tree growth in Scotland. In 1864 this horse chestnut was 8 feet 7 inches in girth, and was believed to have been planted in the year 1687; therefore, if it still stands, it is now 226 years old.

Another sign of the adaptability of the horse chestnut to British environment is the freedom with which it ripens its large fruit and reproduces itself from self-sown seed wherever it gets a chance. The facility with which it does so has caused this tree to be deemed indigenous in many parts of Europe and Asia where it certainly is not a native, but where it has been planted originally on account of its beauty. Further confusion has arisen from the botanists LinnÆus and De Candolle having failed to distinguish the Indian horse chestnut (Æ. indica) from the Greek species, and having assigned Northern Asia as the native region of the latter.

It would not be difficult to mention many individual horse chestnuts in the British Isles exceeding 100 feet in height; probably this tree, if subjected to forest conditions, would grow far loftier than that; but, as it is usually planted exclusively for ornament, it is most often found standing isolated, thereby receiving encouragement to develop enormous side branches and to grow in breadth and bulk rather than in height. Such is the character of a great horse chestnut standing in a group near Moncrieff House, Perthshire. In 1883 this tree measured no less than 19 feet in girth at 5 feet from the ground; but at 10 feet it divides into three huge limbs, each girthing 10 feet, and covers a space nearly 100 yards in circumference. The soil in this district is cool and the climate humid, very different from the conditions at Ashridge in Hertfordshire, where the soil is chalky and hot; yet there is in that fine park a horse chestnut even more massive than the Moncrieff House specimen, being about 80 feet high, and measuring 20 feet in girth. Probably the loftiest horse chestnut in Britain, perhaps in the world, is one at Petworth, in Sussex, which, having been drawn up in close forest, now measures between 115 and 120 feet in height.

It is a pity that this noble tree does not more often receive encouragement to upward growth, seeing that if the surrounding trees are cleared away judiciously, that is not too suddenly, after the horse chestnut has reached a good height, it then feathers down in the most charming manner. It is very seldom that, without discipline of this kind, it will put its energy into height, and attain the fine proportions of a specimen at Biel, in East Lothian. In 1884 this grand tree, probably the loftiest in Scotland, measured 102 feet in height, with a clean bole of 40 feet. It is worth any amount of trouble to secure this character in the horse chestnut, which is an inveterate spreader if allowed licence; and the tendency may be checked by knocking side buds off the stem in the sapling stage, and timely pruning as the tree goes on to maturity.

As an avenue tree, the horse chestnut has few, if any, superiors. Perhaps the finest examples in Scotland of this manner of planting it are to be seen at Gilmerton, in East Lothian, and Drummond Castle, in Perthshire; while in England the splendid double avenue at Bushey Park, Middlesex, has long been famous, "Chestnut Sunday" being a noted festival for Londoners when the trees are in full bloom. The horse chestnut, however, is not a long-lived tree, and cannot be reckoned upon to survive beyond 250 years. The Bushey Park chestnuts are failing fast, many having died already and been replaced by saplings.

Talking of avenues, it is worth while to note a calamity described by Mr. Hutchison of Carlowrie in the Transactions of the Highland and Agricultural Society for 1884. He states there that in 1867 an avenue of horse chestnuts was planted as an approach to the cemetery of Wimborne, Dorsetshire, the trees being set 25 feet apart in the rows. In 1875 it was thought to improve the avenue by planting yews in the intervals between the chestnuts, which had this unfortunate result, that the chestnuts, which had previously thriven finely, all pined away and died.

It is on record that the horse chestnut was first brought to France in 1615, and probably found its way into England about the same time. It seems that it was expected to rank with walnuts and Spanish chestnuts as a fruit tree, a notion which was speedily dispelled. John Evelyn, however, with a right taste for sylvan beauty, early discerned its decorative merit, writing about it in 1663 as follows:

"In the meantime I wish we did more universally propagate the horse chestnut, which being increased from layers, grows into a goodly standard, and bears a glorious flower, even in our cold country. This tree is now all the mode for the avenues to their country places in France."

Travellers in that fair land will remember with pleasure the fine use still made of this tree beside some of the high roads. Between Tours and Blois the wayside has been planted with a chestnut unknown to Evelyn, for it did not exist anywhere in his day. This is the red horse chestnut (Æsculus carnea), which seems to have originated in Germany about the beginning of the nineteenth century, and is believed to be a hybrid between Æ. hippocastanum and the North American shrub Æ. pavia. It is a most beautiful tree, the flowers being of a delightful shade of bright carmine. We are told not to expect it to attain the stature of the common horse chestnut, so it would be well, in designing an avenue, not to mix the red and the white with a view to matching them in height; but the red hybrid has already risen to 50 feet high at Barton in Sussex, and I entertain an idea that this tree may develop into larger proportions than is expected of it, when planted in good soil and favouring shelter. At all events, some which I planted about thirty years ago are now quite as large as common horse chestnuts of the same age.

Mr. Elwes recommends the horse chestnut for planting in towns, remarking that "next to the plane it is one of the best trees we have for this purpose, and does not seem to suffer much from smoke." I regret that I am unable to endorse this view. It is true that in towns of moderate size, and in country villages, horse chestnuts may be planted with excellent effect. I know of few more charming sights than is presented by the group of these trees in the high street of Esher when they are in flower; but in London horse chestnuts prove a lamentable failure. Living as I used to do in the neighbourhood of Sloane Street, it was a distress to me each year to watch the stunted, round-headed chestnuts in the gardens at the lower part of that thoroughfare, and in Eaton Square, unfolding their delicate fingers only to have them parched and blackened by the ruthless drought and dirt of the Metropolis.

As a timber producer, the horse chestnut cannot be assigned high rank. There is no lack of quantity, for the tree increases very rapidly in bulk, but in quality the wood is soft, weak, and very perishable. Moreover, it is almost useless as fuel, and probably the only economic purpose to which it could be applied profitably is the production of wood-pulp and celluloid.

The true meaning of the prefix "horse," by which this tree is distinguished from the true or Spanish chestnut, has been the subject of much discussion. Apparently it was not applied in the sense of "coarse, large," as in the terms horse-radish, horse-mushroom, etc., for the Turkish name for it is at kastan, signifying horse-chestnut; and this was explained in a letter written by the Flemish Dr. Quackleben to Matthiolus in 1557 (many years before the tree was known in Britain), explaining the use of the fruit as a specific against broken wind in horses.