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September 2021 - Sweet Chestnut


Sweet Chestnut


Opposite the top of the ramped entrance is a small tree which is covered in clusters of pale green, spiky pods, known as burrs. These stand out in marked contrast to the long, shiny, dark green leaves, with saw-like edges. This striking tree is a variegated Sweet Chestnut, a slightly smaller version of the standard Sweet Chestnut, which differs by having cream coloured margins to the leaves.

Photo by Bruce Larner - Click to enlarge

The Sweet Chestnut (or Spanish Chestnut as it’s sometimes known) is not a native tree and was commonly thought to have been introduced to Britain by the Romans. Although this is currently up for debate, it has clearly been here for many hundreds of years and has become naturalised, particularly in southern England.


It is a large, fairly quick growing tree that can get up to 35m tall (slightly less for the variegated variety) and live for as long as 700 years. As a mature tree it is very statuesque, with a broad canopy, the widespread branches sometimes almost reaching the ground. And whilst the bark of younger trees is smooth, as it ages, it develops deep fissures which spiral around the trunk and are covered with woody excrescences. The trunks themselves attain a massive girth relative to their height. To see examples of beautiful, mature Sweet Chestnuts, you need travel no further than Mottisfont, where they also have the huge, venerable Plane tree, (one of the largest in the country), and some very old Mulberry Trees.


Sweet Chestnuts and Horse Chestnuts are not related although there are similarities between the burrs and nuts. But whereas the Sweet Chestnut has a very spiny burr containing 2 to 4 nuts that are triangular in outline, being flattened on one surface, the Horse Chestnut, has a tough, thick- skinned burr with fewer spines and one or two much more spherical nuts. It’s the nuts of the Sweet Chestnut that are edible, preferably roasted to remove any bitterness, whereas those of the Horse Chestnut are toxic, but spot on for playing conkers!


The leaves and flowers of the 2 species are also very different. The Sweet Chestnut has long creamy white, catkins that mature in July. Some of the catkins comprise entirely male flowers and these mature first; others also have smaller female flowers at their base. The flowers give off an aroma, not thought to be very attractive, except to their essential allies, pollinating insects! Once fertilised, the female flowers develop into the clusters of green spiny burrs that gradually turn a yellowy brown as they ripen, and then fall to the ground and split open. This usually happens around December, which is why chestnuts are associated with the festive season.

Photo by Bruce Larner - Click image to enlarge 


The leaves of the Sweet Chestnut are also very distinctive. They are long and lance shaped with a glossy surface and very jagged edges, as distinct from the palmate (5 lobed) leaves of the Horse Chestnut.


Although originally from the mountainous regions of Southern Europe, the tree has been grown here for centuries, for it’s nuts, timber, medicinal properties and for tannin and charcoal. It was cultivated extensively in Kent and East Sussex until quite recently, where it was regularly coppiced to provide, amongst other things, fence palings, roof shingles and hop poles; the latter being essential to the brewing industry. A significant area of Chestnut coppice was found to have existed around Canterbury Cathedral by the 1200s. The tree was reputedly made popular in Scotland by Mary, Queen of Scots and it did become fashionable for large estate owners in the seventeenth century to plant Sweet Chestnuts in their grounds.


The Sweet Chestnut flowers are very attractive to bees and other pollinators and over 70 species of moth have been found to feed on the tree during their larval stage, although it isn’t necessarily their primary food plant. The nuts are much appreciated by red squirrels, sadly no longer a part of our local fauna.


As with so many of our trees, the Sweet Chestnut is now at risk from an invasive ‘pest’. The Oriental Gall Wasp was first discovered in the UK in 2015 and was thought to have been introduced on imported plants. The galls appear on buds and leaves and can weaken, and eventually kill the tree. The RHS is running a citizen science project alongside Coventry University to try to save at-risk Sweet Chestnuts. If you’re interested in helping to protect these magnificent trees, please log on to the RHS website to find out more.

Words by Denise Long

Photos by Bruce Larner





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