London Trees & Shrubs – Sweet Chestnut
also see Horse Chestnut
also see Fruit Trees
Castanea sativa or sweet chestnut is a species of flowering plant in the family Fagaceae, native to Europe and Asia Minor, and widely cultivated throughout the temperate world. A substantial, long-lived deciduous tree, it produces an edible seed, the chestnut, which has been used in cooking since ancient times.
The tree is commonly called the “chestnut”, or “sweet chestnut” to distinguish it from the horse chestnut Aesculus hippocastanum, to which it is only distantly related. Other common names include “Spanish chestnut”, “Portuguese chestnut” and “marron” (French for “chestnut”). The Latin sativa means “cultivated by humans”. Some selected varieties are smaller and more compact in growth yelding earlier in life with different ripening time: the Marigoule, the Marisol and the Maraval.
C. sativa attains a height of 20–35 m (66–115 ft) with a trunk often 2 m (7 ft) in diameter. The bark often has a net-shaped (retiform) pattern with deep furrows or fissures running spirally in both directions up the trunk. The oblong-lanceolate, boldly toothed leaves are 16–28 cm (6–11 in) long and 5–9 cm (2–4 in) broad.
The flowers of both sexes are borne in 10–20 cm (4–8 in) long, upright catkins, the male flowers in the upper part and female flowers in the lower part. In the northern hemisphere, they appear in late June to July, and by autumn, the female flowers develop into spiny cupules containing 3-7 brownish nuts that are shed during October. The female flowers eventually form a spiky sheath that deters predators from the seed. Some cultivars (‘Marron de Lyon’, ‘Paragon’ and some hybrids) produce only one large nut per cupule, rather than the usual two to four nuts of edible, though smaller, size.
The tree requires a mild climate and adequate moisture for good growth and a good nut harvest. Its year-growth (but not the rest of the tree) is sensitive to late spring and early autumn frosts, and is intolerant of lime. Under forest conditions, it will tolerate moderate shade well.
This tree responds very well to coppicing, which is still practised in Britain, and produces a good crop of tannin-rich wood every 12 to 30 years, depending on intended use and local growth rate. The tannin renders the young growing wood durable and resistant to outdoor use, thus suitable for posts, fencing or stakes. The wood is of light colour, hard and strong. It is used to make furniture, barrels (sometimes used to age balsamic vinegar), and roof beams notably in southern Europe (for example in houses of the Alpujarra, Spain, in southern France and elsewhere). The timber has a density of 560 kg per cubic meter, and due to its durability in ground contact is often used for external purposes such as fencing. It is also a good fuel, though not favoured for open fires as it tends to spit.
Tannin is found in the following proportions on a 10% moisture basis: bark (6.8%), wood (13.4%), seed husks (10 – 13%). The leaves also contain tannin.
The great English horticulturalist Edward Step had this to say about the Sweet Chestnut.
Sweet Chestnut (Castanea sativa).
When Step was writing at the end of the 1900’s the middle of the last century he refers to is the 1850’s.
Until about the middle of the last century the Chestnut was generally regarded as a genuine native of these islands. It is true that botanists felt that so large and longevous a tree, if native, should be found in the natural forests of this country, or even forming pure forest. These things they did not find, but, on the other hand, they were shown beams in ancient buildings, including Westminster Abbey, which were believed to be Chestnut-wood, and this evidence seemed to point to the fact that Chestnut timber was grown much more plentifully in this country at the period when these old buildings were erected. Dr. Lindley, however, set the matter at rest by examination of the reputed Chestnut beams in the roof of Westminster Abbey, and proved that they were of Durmast Oak. A similar examination of the timbers of the old Louvre in Paris, which were also reputed to be Chestnut, gave a similar result. A comparison of sections across the grain of Oak and Chestnut allows of no possibility of mistake, and it is now known that whilst the wood of young Chestnuts is tough and durable, that from old trees is brittle and comparatively worthless, except for firewood, which is exactly the opposite of Oak-wood. It is now generally agreed that its real home is in Asia Minor and Greece, whence it was introduced to Italy in very remote times, and has since spread over most of temperate Europe, its seeds ripening and sowing themselves wherever the vine flourishes. We appear to be indebted to our friends the Romans for its introduction to Britain, who no doubt hoped to utilize the fruit for food, as at home—a hope that must have been disappointed, for its crops, even in the South of England, are very fitful, and the nuts quite small.
Sweet Chestnut—summer and winter.
Bole of Sweet Chestnut.
In suitable situations the Chestnut is of larger proportions and greater length of life even than the Oak. In the South of England it will attain a height of from sixty to eighty feet in fifty or sixty years, and if growing in deep porous loam, free from carbonate of lime, and sheltered from strong winds and frosts, it builds up an erect massive column. Hamerton has said of such a tree: “His expression is that of sturdy strength; his trunk and limbs are built, not like those of Apollo, but like the trunk and limbs of Hercules.” Under less suitable conditions the undivided trunk is little more than ten feet long; then it divides off into several huge limbs, and so the general character of the tree is altered, and it presents much the appearance of having been pollarded. The branches have a horizontal and downward habit of growth, the extremities of the lowest ones often being but little above the earth. The fine elliptical leaves are nine or ten inches in length, of a rich green, that is enhanced by the polished surface, which “brings up” the colour. Their edges are cut into long pointed teeth. Towards autumn they pale to light yellow, and then deepen into gold on their way to the final brown of the fallen leaf, which, by the way, is a great enricher of the soil where the Chestnut is grown.
Sweet Chestnut. A, fruit.
The flowers, though individually small and inconspicuous, are rather striking, from their association in cylindrical yellow catkins, about six inches long, which hang from the axils of the leaves. The upper part of this catkin consists of male flowers, each with a number of stamens enclosed in a perianth or calyx of five or six green leaves. The female flowers, on the lower part of the catkin, are two or three together, in a prickly four-lobed “cupule,” or involucre, and consist each of a calyx closely investing a tapering ovary, whose summit bears from five to eight radiating stigmas, the number corresponding with the cells into which the ovary is divided. Each cell contains two seed-eggs, but as a rule only one in each flower develops. As development of the ovary and seeds progresses, the cupule also grows, and ultimately entirely surrounds the cluster with the hedgehog-like coat in which the nuts are contained when ripe. Then it splits open and discloses the two or three glossy brown nuts. The Chestnut is in flower from May to July, and the nuts drop in October. They form an important article of food in South Europe, where they are produced in abundance, and there can be little doubt that the importers of the tree to this country believed it would prove equally valuable here. Evelyn had this in mind when he recommended the nut as “a lusty and masculine food for rustics at all times, and of better nourishment for husbandmen than cole and rusty bacon.” Well, there is plenty of Chestnut grown around Evelyn’s estate at Wootton to-day, but it is chiefly as coppice, to provide hop-poles, and hoops for barrels, for which purpose the long straight shoots are split in two. Grown as coppice, the Chestnut also provides fine cover for pheasants and other game. The trees begin to bear when about twenty-five years old, and from thence on to the fiftieth or sixtieth year the timber is at its best, but later it develops the defect known as “ring shake,” and becomes of little use. That is probably why one meets with so many hollow wrecks of what were once noble Chestnuts.
The young wood is covered with smooth brown bark, but later this becomes grey, and its surface splits into longitudinal fissures, which give a very distinctive character to the trunk. In older trees the fissures and the alternating ridges have a slight spiral twist, which gives the tree the appearance (shown in our third photo) of having been wrenched round by some mighty force. The average age of the Chestnut is about five hundred years, but there have been in this country many old trees that were much older, if any reliance could be placed in local tradition. There was—we fear there is little of it still remaining—the great Tortworth Chestnut in Lord Ducies’ park at Tortworth Court. In 1820 it was found to have a girth of fifty-two feet. Evelyn refers to it in his “Sylva,” and tells us that in the reign of King Stephen it already bore the title of the Great Chestnut of Tortworth.
The name Chestnut appears to be a modification of the old Latin name Castanea, through the French form Chataigner. The Latin is said to be derived from Kastanum, a town in Thessaly, but it is more likely that the presence of Chestnut-trees gave a name to the town, as has happened so many times in our own country with various trees, the Chestnut included.