Sweet chestnut
The sweet chestnut, also known as the Spanish chestnut or European chestnut, is a species of tree in the family Fagaceae, native to Southern 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.
Description
Castanea sativa attains a height of with a trunk often in diameter. Around 20 trees are recorded with diameters over including one in diameter at breast height. A famous ancient tree known as the Hundred Horse Chestnut in Sicily was historically recorded at in diameter. The bark often has a net-shaped pattern with deep furrows or fissures running spirally in both directions up the trunk. The trunk is mostly straight with branching starting at low heights. The oblong-lanceolate, boldly toothed leaves are long and broad.The flowers of both sexes are borne 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. The sweet chestnut is naturally self incompatible, meaning that the plant cannot pollinate itself, making cross-pollination necessary. Some cultivars only produce one large seed per cupule, while others produce up to three seeds. The nut itself is composed of two skins: an external, shiny brown part, and an internal skin adhering to the fruit. Inside, there is an edible, creamy-white part developed from the cotyledons.
Sweet chestnut trees live to an age of 500 to 600 years. In cultivation they may even grow as old as 1,000 years or more.
Taxonomy
The tree is to be distinguished from the horse chestnut Aesculus hippocastanum, to which it is only distantly related. The horse chestnut bears superficially similar but inedible seeds in a dehiscent seed case. Other common names include "Spanish chestnut" or "marron". The generic name Castanea is the old Latin name for the plant species, while the specific epithet sativa means "cultivated by humans". Some selected varieties are smaller and more compact in growth yielding earlier in life with different ripening time: the Marigoule, the Marisol and the Maraval.Distribution and habitat
The species is native to Southern Europe and Asia Minor. It is found across the Mediterranean region, from the Caspian Sea to the Atlantic Ocean. It is thought to have survived the last ice age in several refuges in Southern Europe, on the southern coast of the Black Sea with a main centre on the southern slope of the Caucasus and in the region of north-western Syria, possibly extending into Lebanon.The species is widely distributed throughout Europe, where in 2004 it was grown on of forest, of which were mainly cultivated for wood and for fruit production. In some European countries, C. sativa has only been introduced recently, for example in Slovakia or the Netherlands.
The tree requires a mild climate and adequate moisture for good growth and a good nut harvest. Its year-growth is sensitive to late spring and early autumn frosts; it is also intolerant of lime. Under forest conditions, it will tolerate moderate shade well. It can live to more than 2,000 years of age in natural conditions, such as the Hundred Horse Chestnut near Mount Etna in eastern Sicily.
Ecology
The leaves provide food for some animals, including Lepidoptera such as the case-bearer moth Coleophora anatipennella and North American rose chafer Macrodactylus subspinosus.The two major fungal pathogens of the sweet chestnut are the chestnut blight and the ink disease caused by Phytophthora cambivora and P. cinnamomi. In North America as well as in Southern Europe Cryphonectria parasitica destroyed most of the chestnut population in the 20th century. With biological control, the population of the sweet chestnut is not threatened anymore by the chestnut blight and is regenerating. Ink disease is infesting trees mostly in humid soils, with the mycelium invading the root and resulting in wilting of the leaf. Absence of fruit formation leads to die back of the petal. The ink disease is named after the black exudates at the base of the trunk. Nowadays there are cultivars that are resistant to the ink disease. Phytophthora cambivora caused serious damage in Asia and the US, and it still continues to destroy new plantations in Europe.
Another serious pest which is difficult to control is the gall wasp which was recently introduced in Southern Europe, originating in Asia.
Cultivation
History
Pollen data indicates that the first spreading of Castanea sativa due to human activity started around 2100–2050 B.C. in Anatolia, northeastern Greece and southeastern Bulgaria. Compared to other crops, the sweet chestnut was probably of relatively minor importance and distributed very heterogeneously throughout these regions. The first charcoal remains of sweet chestnut only date from around 850–950 B.C., making it very difficult to infer a precise origin history. A newer but more reliable source are the literary works of Ancient Greece, with the richest being Theophrastus's Historia plantarum, written in the third century B.C. Theophrastus focuses mainly on the use of sweet chestnut wood as timber and charcoal, only mentioning the use of the fruit once when commenting on the digestive difficulties it causes, but praising its nourishing quality. Several Greek authors wrote about medicinal properties of the sweet chestnut, specifically as a remedy against lacerations of the lips and of the oesophagus.Similar to the introduction of grape vine and olive cultivation to the Latin world, C. sativa is thought to have been introduced during the colonisation of the Italian peninsula by the Greeks. Further clues pointing to this theory can be found in the work of Pliny the Elder, who mentions only Greek colonies in connection with sweet chestnut cultivation. Today's phylogenetic map of the sweet chestnut, while not fully understood, shows greater genetic similarity between Italian and western Anatolian C. sativa trees compared to eastern Anatolian specimen, reinforcing these findings. Nonetheless, until the end of the pre-Christian era, the spread and use of the chestnut in Italy remained limited. Carbonised sweet chestnuts were found in a Roman villa at Torre Annunziata near Naples, destroyed by the eruption of Mount Vesuvius in A.D. 79.
Clues in art and literature indicate a dislike of the sweet chestnut by the Roman aristocracy. Like Theophrastus, Latin authors are sceptical of the sweet chestnut as a fruit, and Pliny the Elder even goes as far as admiring how well nature has hidden this fruit of apparently so little value. In the beginning of the Christian era, people probably started to realize the value and versatility of sweet chestnut wood, leading to a slow spread of the cultivation of C. sativa trees, a theory that is supported by pollen data and literary sources, as well as the increased use of sweet chestnut wood as poles and in supporting structures, wood works and pier building between A.D. 100 and 600.
Increasing sweet chestnut pollen appearances in Switzerland, France, Germany and the Iberian peninsula in the first century A.D. suggests the spreading of cultivated sweet chestnut trees by the Romans. Contrary to that notion, other scientists found no indication of the Romans spreading C. sativa before the fifth century. While the husks of sweet chestnuts, dated to the third or early fourth century, have been identified from the bottom of a Roman well at Great Holts Farm, in Boreham in Essex, England; this deposit includes remains of other exotic food plants and provides no evidence that any of them originated locally. No other evidence of sweet chestnut in Roman Britain has been confirmed. Indeed, no centre of sweet chestnut cultivation outside the Italian peninsula in Roman times has been detected. Widespread use of chestnut in western Europe started in the early Middle Ages and flourished in the late Middle Ages. In the mid-seventh-century Lombard laws, a composition of one solidi is set for felling a chestnut tree belonging to another person. Since the beginning of the 20th century, due to depopulation of the countryside and the abandonment of the sweet chestnut as a staple food as well as the spread of chestnut blight and ink disease, C. sativa cultivation has dramatically decreased. Nowadays, sweet chestnut production is sometimes seen at a turning point again, because the development of high-value sweet chestnut products combined with changing needs of an urban society is leading to a revival in its cultivation.
Cultivation forms
Three different cultivation systems for the sweet chestnut can be distinguished:- Coppicing: Mainly for wood extraction. Standard conditions yield 15 m3 wood per ha per year.
- Selve: Fruit production from grafted trees. The trees have a short tribe and a big crown. Trees have a high density and the ground between the trees is often used as pasture.
- High forest: Wood and fruit production. This cultivation form is less intensive with a yield of 4–12 dt/ha and replacement of trees every 50–80 years. The trees grow from seeds and build a dense canopy.