🌰 Sweet Chestnut Castanea sativa
This is a guide, not a substitute for expert identification. Foraging guides - including this one - can contain errors. If you are not completely certain of an identification, do not eat it. Cross-check against at least two independent sources, and when in doubt, consult a local foraging expert or an experienced forager in person before eating anything wild.
A large, long-lived woodland tree producing edible nuts in autumn inside distinctively spiny cases; easily confused by name with the unrelated and inedible horse chestnut, so correct identification of the case and leaf is essential.
Identification
Sweet chestnut is a large deciduous tree, capable of reaching great size and age, with distinctive deeply-fissured, often spirally-ridged grey-brown bark on mature trunks. Leaves are long, narrow to oval, and sharply and evenly serrated (saw-toothed) along the edge, arranged singly (not in a hand-shaped cluster). In summer it produces long, pale yellow-green catkins with a distinctive musky scent. The nuts form inside a dense, tightly-packed spiny case (cupule) covered all over with long, thin, sharp spines; each case usually contains two or three nuts, which are glossy, deep reddish-brown, and flattened with a pointed tip.
⚠️ Dangerous look-alikes - read this before picking anything
The critical look-alike is horse chestnut (Aesculus hippocastanum), whose seeds ('conkers') are inedible and mildly toxic to humans (containing the compound aesculin, which causes gastrointestinal upset) - they are a different species entirely, unrelated to true chestnuts despite the shared common name. Verified identification differences: horse chestnut leaves are large and hand-shaped (palmate), made up of 5-7 finger-like leaflets radiating from a central point, completely unlike sweet chestnut's single long serrated leaf. The spiky case is the fastest field check: sweet chestnut cases are densely covered in many thin, sharp, needle-like spines covering the whole surface, while horse chestnut cases have far fewer, shorter, thicker, more widely-spaced and blunter spines with bare patches of case visible between them. The nut itself also differs: sweet chestnuts are smaller, flattened with a pointed tip, usually 2-3 to a case, while a conker is a single large, smooth, round, glossy nut with a pale scar patch and no point. If the case has only a few stubby spines and a bare, leathery surface between them, or the leaves are hand-shaped rather than a single serrated blade, treat it as horse chestnut and do not eat the nut.
UK habitat
Sweet chestnut grows in woodland across the UK, especially in southern England, and is a long-established naturalised tree (introduced by the Romans, though not native) that is widely planted and often actively coppiced. It favours well-drained, slightly acidic soils and is a common component of managed and semi-natural broadleaf woodland.
Legal notes
Not protected under the Wildlife and Countryside Act 1981 Schedule 8 - sweet chestnut is a common, naturalised, unprotected tree. Picking fallen nuts (fruit) for personal use from wild-growing trees is not theft under Theft Act 1968 s4(3), provided it is not for commercial sale or reward. This covers fruit only, not felling, damaging, or uprooting the tree without the landowner's permission. See the full UK foraging law guide for the general rules.