Spanish chestnut

Castanea sativa, or sweet chestnut, is a species of flowering plant 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. 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 yielding 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 trunk is mostly straight with branching starting at low heights. Sweet chestnut trees live to an age of 500 to 600 years. If cultivated, sweet chestnut trees might even grow as old as 1000 years or more. Their large genetic diversity and different cultivars are being nursed for uses like flour, boiling, roasting, drying, candying or wood. 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. The sweet chestnut is self incompatible, meaning that the plant can’t pollinate itself, making cross-pollination necessary. Some cultivars only produce one large nut per cupule, while others produce up to three nuts. 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 cotyledon. 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. It can live to more than 2,000 years of age in natural conditions, see the poetically-named 'hundred-horse chestnut' in eastern Sicily for example. The leaves provide food for some animals, including Lepidoptera such as the case-bearer moth Coleophora anatipennella and 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 Phytophthora 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 USA, and it still continues to destroy new plantations in Europe. Another serious pest which is difficult to control is the gall wasp (Dryocosmus kuriphylus) which was recently introduced in Southern Europe, originating from Asia.