Chestnut - Description

Description

Chestnut trees are of moderate growth rate (for the Chinese chestnut tree) to fast-growing for American and European species. Their mature heights vary from the smallest species of chinkapins, often shrubby, to the giant of past American forests, Castanea dentata that could reach 60 m. In between these extremes are found the Japanese chestnut (Castanea crenata) at 10 m average; followed by the Chinese Chestnut (Castanea mollissima) at about 15 m, then the European chestnut (Castanea sativa) around 30 m.

The Chinese and more so the Japanese chestnuts are both often multileadered and wide-spreading, whereas European and especially American species tend to grow very erect when planted among others, with little tapering of their columnar trunk, which is firmly set and massive. When standing on their own, they spread on the sides and develop broad, rounded, dense crowns at maturity. The two latter's foliage has striking yellow autumn colouring.

Its bark is smooth when young, of a vinous maroon or red-brown colour for the American chestnut, grey for the European chestnut. With age American species' becomes grey and darker, thick and deeply furrowed; the furrows run longitudinally, and tend to twist around the trunk as the tree ages; it sometimes reminds one of a large cable with twisted strands.

The leaves are simple, ovate or lanceolate, 10–30 cm long and 4–10 cm wide, with sharply pointed, widely-spaced teeth, with shallow rounded sinuates between.

The flowers follow the leaves, appearing in late spring or early summer or onto July. They are arranged in long catkins of two kinds, with both kinds being borne on every tree. Some catkins are made of only male flowers, which mature first. Each flower has eight stamens, or 10 to 12 for Castanea mollissima. The ripe pollen carries a heavy sweet odour that some people find too sweet or unpleasant. Other catkins have these pollen-bearing flowers, but also carry near the twig from which these spring, small clusters of female or fruit-producing flowers. Two or three flowers together form a four-lobed prickly calybium, which ultimately grows completely together to make the brown hull, or husk, covering the fruits.

The fruit is contained in a spiny (very sharp) cupule 5–11 cm in diameter, also called "bur" or "burr". The burrs are often paired or clustered on the branch and contain one to seven nuts according to the different species, varieties and cultivars. Around the time the fruits reach maturity, the burrs turn yellow-brown and split open in 2 or 4 sections. They can remain on the tree longer than they hold the fruit, but more often achieve complete opening and release the fruits only after having fallen on the ground; opening is partly due to soil humidity.

The chestnut fruit has a pointed end with a small tuft at its tip (called "flame" in Italian), and at the other end, a hilum – a pale brown attachment scar. In many varieties, the fruit is flattened on one or two sides. It has two skins. The first one is a hard outer shiny brown hull or husk, called the pericarpus; the industry calls this the peel. Underneath the pericarpus is another thinner skin, called the "pellicle" or "episperm". The pellicle closely adheres to the seed itself, following the grooves usually present at the surface of the fruit. These grooves are of variable sizes and depth according to the species and variety.

The fruit inside these shows two cotyledons with a creamy-white flesh throughout, except in some varieties which show only one cotyledon, and whose episperm is only slightly or not intruded at all. Usually these varieties have only one large fruit per burr, well rounded (no flat face) and which is called "marron" ("marron de Lyon" in France, "marron di Mugello" in Italy, or "Paragon").

The superior fruiting varieties among European chestnuts have good size, sweet taste and easy-to-remove inner skins. American chestnuts are usually very small (around 5 g), but sweet-tasting with easy-to-remove pellicles. Some Japanese varieties have very large nuts (around 40 g), with typically difficult-to-remove pellicles. Chinese chestnut pellicles are usually easy to remove, and their sizes vary greatly according to the varieties, although usually smaller than the Japanese chestnut.