Castanea sativa, sweet chestnut
Sweet Chestnut is a species of flowering tree 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 for millennia. Hardy to -29°C
The tree is deciduous and grows to 20–35 m with a trunk often 2 m in diameter. The bark often has a net-shaped pattern with deep furrows or fissures running spirally in both directions up the trunk. The oblong-lanceolate, boldly toothed leaves are 16–28 cm long and 5–9 cm broad.
The annual growth is sensitive to late spring and early autumn frosts and is intolerant of Alkaline soils. Under forest conditions, it will tolerate moderate shade well and win through to become part of the climax canopy in the process of succession .
The flowers of both sexes are borne on the same tree in 10–20 cm 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 1-7 brownish nuts that are shed during October. The female flowers eventually form a spiky sheath that deters predators from the seed. Chestnut tree flowers are also an important source of pollen for bees in some regions including ours, some honey producers harvest just after the chestnut flowers are starting their transformation and label the honey as chestnut honey, which does have a flavour very much its own.
The fruit chestnuts have a skin which is astringent and unpleasant to eat when still moist; after drying for a time the thin skin loses its astringency but is still better removed to reach the white fruit underneath. Cooking dry in an oven or fire normally helps remove this skin. Chestnuts are traditionally roasted in their tough brown husks after removing the spiny cupules in which they grow on the tree, the husks being peeled off and discarded and the hot chestnuts dipped in salt before eating them. Roast chestnuts are traditionally sold in streets, markets and fairs by street vendors.
The skin of raw peeled chestnuts can be relatively easily removed by quickly blanching the nuts after scoring them by a cross slit at the tufted end. Once cooked, chestnuts acquire a sweet flavour and a floury texture. The cooked nuts can be used for stuffing poultry, as a vegetable or in nut roasts. They can also be used in confections, puddings, desserts and cakes. They are used for flour, bread making, a cereal substitute, roasted for a coffee substitute, a thickener in soups and other cookery uses, as well as for fattening stock. A sugar can be extracted from them. A local variety of Corsican beer also uses chestnuts and a brewer local to us makes a chestnut beer every year for the chestnut festival in Eguzon. A product is sold as a sweetened paste mixed with vanilla, crème de marron, sweetened or unsweetened as chestnut purée or purée de marron, and candied chestnuts as marrons glacés.
Chestnuts are similar in nutritional value to rice or wheat and can produce in the region of two tons of nuts per acre with the advantage of not having to cultivate and kill the soil year after year, instead the soil is built and improved every year. Our hedge trees are untreated and produce nuts every year which we use for our own consumption and fodder for cows, sheep and pigs.
Some cultivars (‘Marron de Lyon’, ‘Paragon’ and some other hybrids) produce only one large nut per cupule, rather than the usual two to four nuts of edible, though smaller, size. Dorei de Lyon and Nouzillarde are two of the recent cultivars we have added to our chestnut tree collection with more to follow soon, the rest of our chestnut trees are simply the local wild trees many of which have self seeded. The self seeded trees which grow in open spaces are carefully excavated and replanted in new hedgerows to provide more shade and fodder for livestock and wildlife.
The wood, this tree responds very well to coppicing, which is still practised extensively in France, and produces a good crop of tannin-rich wood every 7 to 20 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 like the ones we used in our roundhouse and straw bale house this year. I have used the wood for tool handles and Windsor chair legs.