Chestnut is a genus of eight or nine species that belong to the family Fagaceae scientifically known as Castanea. The species are deciduous trees or shrubs and are native to the temperate regions of the Northern Hemisphere. The fruits are edible. Four species are more frequently known namely European, Chinese, Japanese and American chestnuts. They should not be confused with the horse chestnuts which are unrelated to this genus but are named due to the similar appearance of the nuts which are inedible. They should not be mixed with water chestnuts as the tubers of both the plants bear similar tastes. The scientific name has got its origin from a Latin word.
Generally the chestnut trees grow at a moderate rate but the American and European species grow at a faster rate. They may attain a height of 10 m to 60 m. the bark is smooth when the plant is smooth but becomes vinous red or brown when mature. American species become deeply furrowed, thick as the plant attains maturity. The leaves may be simple, oval or lanceolate. They measure10-30 cm in length and 4-10 cm in width and are provided with sharp teeth with shallow sinuates between the teeth. The flowers appear either in late spring or in early summer. The flowers are arranged in long catkins which may be of two types. Both types of catkins are borne by a single plant. Some catkins bear only male flowers which mature first. Each male flower bears 8-10 stamens. The pollens bear a characteristic odour that may be sweet or unpleasant for some individuals. Other catkins also bear female or fruit producing flowers on a small twig along with the male flowers. Two o more flowers together form a four-lobed prickly calybium which ultimately forms husk covered fruit.
The fruit is also known as burr and is a spiny cupule measuring 5-11 cm in diameter. The burrs may be paired or clustered on a twig and bear about 1-7 nuts depending on the species, varieties and cultivars. At maturity the burrs become yellow-brown and open into 2-4 sections or lobes. The fully mature fruits drop on the ground and open only when the soil contains enough moisture. The fruit is provided with a small tuft at one end and a small brown attachment scar known as hilum at the other end. In many varieties the fruit may be flattened on either side. The fruit has two skins. The outer one is hard and shiny husk called as pericarpus. Just beneath the pericarpus is a thin episperm which is attached to the seed. There are generally two cream coloured cotyledons but in some varieties there is only one cotyledon. Each 100 grams of fresh fruit yield about 180 calories. They lack cholesterol and very little unsaturated fat with no gluten. They contain twice the amount of starch as compared to that of the potatoes. They contain 8% of sucrose, fructose and glucose. Each 100 gram of chestnut fruit contains 40 mg of vitamin C. fresh fruits contain 52% of water by weight.
