Sweet chestnut

The sweet chestnut (Castanea sativa), also known as the Spanish chestnut or European chestnut, is a species of tree in the family Fagaceae, native to Southern Europe and Anatolia, and widely cultivated in Western and Central Europe. 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 (although it has split into multiple trunks above ground). The bark often has a net-shaped (retiform) 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. In cultivation they may even grow as old as 1,000 years or more. or "marron" (French for "chestnut"). 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 Anatolia. 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 (but not the rest of the tree) is sensitive to late spring and early autumn frosts; it is also intolerant of lime. Under forest conditions, it will tolerate moderate shade well.

Ecology

The leaves provide food for animals including Lepidoptera such as the case-bearer moth Coleophora anatipennella and the North American rose chafer Macrodactylus subspinosus.

The two major fungal pathogens of the sweet chestnut are the chestnut blight (Cryphonectria parasitica) 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. Compared to other crops, the sweet chestnut was probably of relatively minor importance and distributed very heterogeneously throughout these regions. 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. Nonetheless, until the end of the pre-Christian era, the spread and use of the chestnut in Italy remained limited.

Clues in art and literature indicate a dislike of the sweet chestnut by the Roman aristocracy. 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. In the mid-seventh-century Lombard laws, a composition of one solidi is set for felling a chestnut tree (or, also, hazel, pear or apple) belonging to another person (Edictum Rothari, No. 301, 643 AD). 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.

Coppicing: Mainly for wood extraction. Standard conditions yield 15 m<sup>3</sup> wood per ha per year.
Selve: Fruit production from grafted trees. The trees have a short trunk and a large crown. The trees are planted at 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.

The field management is dependent on the cultivation system. While cleaning the soil from the leaves and pruning is the norm, the use of fertiliser, irrigation and pesticides is less common and reserved for more intensive cultivation.

Coppiced sweet chestnut woodland.jpg|Coppice

Castanea sativa orchard in Andalusia, Spain 01.jpg|Orchard

Steni forest-Δάσος Στενής.jpg|Chestnut-oak-pine forest

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Requirements

The sweet chestnut tree grows well on limestone-free, deeply weathered soil. The optimal pH value of the soil is between 4.5 and 6, and the tree cannot tolerate soil compaction. It is a heat-loving tree which needs a long vegetation period. The optimal average temperature is between This is to limit the main storage problems threatening the sweet chestnut, fungi development and the presence of insect larvae. has gained the Royal Horticultural Society's Award of Garden Merit. Cultivars of French origin include Bouche de Betizac, Maraval, Marigoule, Marsol, and Precoce Migoule. Cultivars of American origin include Colossal and Labor Day.

Uses

The species is widely cultivated for its edible seeds (also called chestnuts), and for its wood.

Nutrition

The fat content is low and dominated by unsaturated fatty acids. Sweet chestnut is a good source of starch. The energy value per 100 g (3.5 oz) of C. sativa amounts to 891 kJ (213 kcal) (table). C. sativa nuts are characterised by high moisture content, which ranges from 41% to 59%. The chestnut provides a good source of copper, phosphorus, manganese and potassium (table). Fructose is mostly responsible for the sweet taste.

Roman soldiers were given chestnut porridge before going into battle. Heat appears to be the most influencing factor when it comes to decreasing the organic acid content. However, even after heating sweet chestnuts, antioxidant activity remains relatively high. On the other hand, the consumer must consider that roasting, boiling or frying has a big impact on the nutritional profile of chestnut. Vitamin C content falls by as much as 54% when boiled and by as much as 77% when roasted. Nevertheless, roasted or boiled chestnuts may still be a solid vitamin C source, since 100 grams still represents about 20% of the recommended daily dietary intake.

The sugar content is also affected by the high temperatures. Four processes are decisive for the degrading process of sugar while cooking; hydrolysis of starch to oligosaccharide and monosaccharide, decomposition of sucrose to glucose and fructose, caramelisation of sugars and degradation of sugars. Organic acids are also affected by high temperatures; their content decreases about 50% after frying, and 15% after boiling.

Wood

thumb|Medieval chestnut roof of [[Penshurst Place, Kent, England]]

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 weather resistant for 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 metre, and due to its durability in ground contact is often used for external purposes such as fencing. a kind of alternative medicine promoted for its supposed effect on health. However, according to Cancer Research UK, "there is no scientific evidence to prove that flower remedies can control, cure or prevent any type of disease, including cancer".

References

External links

U.C. Davis, California: Castanea sativa in horticulture
Plants for a Future database: Castanea sativa
Castanea sativa – distribution map, genetic conservation units and related resources. European Forest Genetic Resources Programme (EUFORGEN)