Sweet Chestnut

The only edible chestnut

The sweet chestnut has long played a role in human society. Romans cultivated it to supplement the food given to their legionnaires. Without doubt the sweet chestnut has long been established in the Netherlands but its native habitat is far to the south in a region around the Mediterranean and Black Sea. From the Middle Ages sweet chestnut trees were widely planted in monastery gardens, on estates and in the foothills of mountains such as those on the island of Corsica. The sweet chestnut tree is highly prized for its seeds (nuts) and wood. Roasted chestnuts are extremely tasty and the durable chestnut wood is used to make, amongst other things, sheep pens.

Often there is confusion between the sweet chestnut and the horse chestnut but the only similarity is in the name – chestnut – as the seeds, the nuts, only bear a superficial resemblance to one another.

Sativa means cultivated. The sweet chestnut grows to 20-30 meters high and lives to between 500 and 1,500 years. These trees can tolerate more shade than the oak and can thus attain huge status within an open oak forest. Nowadays the forestry commission grows sweet chestnut within oak woodland as a soil-improving wood species. Here they plan to cut the trees back to stumps as they recover well after such treatment. It is valuable as a coppiced tree species as it can tolerate shade and provides a rich easily decomposable litter.

It is extremely suited for growing in parks, but it is too tall for the garden and too wide for planting along streets. The leaves are large and elongated with a serrated margin. In the autumn the leaf changes colour from yellowish green to golden yellow and rust brown. The tree bears catkins that only appear in June when the tree is in full leaf. The sweet chestnut differs from other catkin bearing trees and bushes in that it is not wind pollinated but insect pollinated. The male catkins have white flowers and only at the base are there a few green female flowers. The flowers are full of nectar and have a distinct fragrance. After flowering the male flowers are shed whilst the pollinated female flowers go on to fruit. Young trees bear fruit when they are approximately 30 years old.

The fruit comprises a sharp spiny husk usually with two seeds, the conkers, which fall from the tree on ripening in October. The underdeveloped chestnuts fall off first. In the Netherlands the harvest is usually optimal only when a mild winter is followed by a warm and wet spring and autumn. The root is a short, thick taproot, which soon branches out into extensive, thick side roots. At the sapling stage the bark is smooth and brown; older trees have bark resembling that of an oak. In mature trees the trunk may twist by as much as 180^o or more - this can be seen in the bark and gives the trees a distinct appearance.