Sweet chestnut

Sweet chestnut: how do you recognise it?

Habit

Tree of 20–30 m with a broad, rounded crown about 18 m across; old trees have a thick, often short trunk.

Leaves

Alternate, lance-shaped, 10–25 cm, with parallel side veins each ending in a bristle-tipped tooth.

Bark

Grey-brown; on old trees with deep, spirally twisted furrows.

Flowers

Long, yellowish-white, strong-smelling catkins in July.

Fruit

Very spiny husk with 1–3 edible chestnuts, ripe in October.

Difference from horse chestnut

Horse chestnut has a palmately compound leaf and inedible conkers in a husk with short spines.

Flowering: June–July · Harvest and fruit: September–October · Pruning: November–March

Identify by feature: Long, narrow leaves · Nuts, acorns and chestnuts

Looks like it, but isn’t

• Horse chestnut Aesculus hippocastanum: palmately compound leaf and inedible conkers. Difference from horse chestnut

Why grow it?

• Edible chestnuts for roasting, as purée or as chestnut flour.
• Flowers in July, when there are few other flowers: a tree busy with bees.
• As coppice it provides durable wood for posts, fencing and cladding.
• With their twisted bark, old trees are true monuments.
• Golden-yellow to brown autumn colour.

Sweet chestnut: where does it grow best?

• Full sun; for a good crop, a warm, sheltered spot.
• Acid, open, free-draining soil such as sandy loam. It tolerates neither lime nor wet ground.
• Allow for 20–30 m in height and a crown of about 18 m: only for a large garden, a farmyard, a meadow or a park.
• As coppice, cut every 10–15 years, it takes up far less space.

Light

Full sun

Legal basis

Acid soil

Moisture

Normal

Size

25 m tall, 18 m wide

Hardiness

Throughout Belgium, no protection needed

Goes well with

• English oak: On acid, loamy sand, oak and sweet chestnut have always grown together in woods and hedgerows.
• Holly: An evergreen understorey that tolerates shade and acid soil.
• Hazel: Another nut tree for the edge, which you can coppice just like the chestnut.
• Rowan: A small native tree with orange-red berries that also likes acid soil.

Sweet chestnut: when and how to plant it?

1. Plant from November to March when the ground isn’t frozen.
2. For chestnuts, choose grafted fruiting varieties: they crop much sooner than a seedling and give bigger nuts.
3. Plant at least two trees or two different varieties near each other: a sweet chestnut pollinates itself poorly.
4. No lime or chalky compost in the planting hole.
5. Put in a stake and water after planting and during dry spells in the first few summers.

Care

Watering

In dry spells during the first few years; rarely needed after that.

Feeding

Not needed; leave the fallen leaves as a natural mulch.

Harvesting

Gather the chestnuts in October as soon as the husks fall and split open; wear sturdy gloves or prise the husks open with your shoe.

Storing

Fresh chestnuts quickly dry out or go mouldy: keep them cool in the fridge and use them within a few weeks, or freeze them.

Coppice

After cutting, keep the strongest shoots on each stool; they soon grow into poles.

Tip: Roasting chestnuts: cut a cross in the skin with a sharp knife so they don’t burst, then roast them in a pan with holes or for 20–25 minutes in a hot oven. Peel them while they are still warm.

Sweet chestnut: when to prune it?

Pruning months: November–March.

When: Dead, diseased and broken branches can be removed at any time of year. Prune or coppice during winter dormancy (November–March).

How:

• As a tree it needs little pruning: give a young tree a single trunk, remove crossing branches and lift the crown gradually.
• Grown as coppice, it can be cut down every 10–15 years, close to the ground; it regrows vigorously.
• Cut out dead and diseased branches back into healthy wood.

Caution: Do most of your pruning while the tree is young: large saw cuts on an old chestnut heal slowly.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Sowing

Sow fresh chestnuts in autumn, 3–5 cm deep, in a pot or where they are to grow, and protect them from mice. A seedling gives smaller and variable nuts.

Grafting

Fruiting varieties are grafted; that is a job for the nursery.

Sweet chestnut: how does it get through the winter?

Hardy throughout Belgium: no protection needed.

• Fully hardy.
• Winter is the season for planting and for cutting coppice.

Diseases and pests

• Oriental chestnut gall wasp: A tiny wasp from Asia that is spreading across Europe. It causes green to red galls on buds and young leaves, which hold back growth and the crop. Cut the galls off young trees in spring.
• Ink disease: A Phytophthora of wet, heavy soil: the tree declines and black fluid oozes from the base of the trunk. Only plant on free-draining soil.
• Maggoty chestnuts: The caterpillars of a small moth eat the nuts from the inside. Gather chestnuts promptly and throw away affected ones.
• Empty husks: Flat, empty chestnuts point to poor pollination: plant a second tree or variety nearby.

Through the year

• January: Prune during dormancy; cut coppice.
• February: Pruning and planting, when there is no frost.
• March: Last month for pruning and planting.
• May: Leaves emerge; watch for galls on young shoots.
• July: Flowering: long, scented catkins full of bees.
• August: Water young trees in dry spells.
• October: Harvest: gather chestnuts as soon as the husks fall; sowing.
• November: Planting season; pruning can start again.
• December: Pruning; cutting coppice.

What can you use it for?

Food and drink

Chestnuts for roasting, as purée or as chestnut flour.

Wood

Durable wood for posts, fencing and cladding.

For wildlife

Flowers in July, when there are few other flowers for bees.

Edible and useful

Nuts (September–October)

Gather the chestnuts from late September to late October, as soon as the spiny husks split and fall. Choose glossy, firm, plump ones. Delicious roasted, in soup, as a purée, in a stuffing or as chestnut spread.

Storing

Fresh chestnuts dry out and go mouldy quickly: keep them for no more than two weeks in a paper bag in the salad drawer of the fridge. To keep them longer, boil or roast them, peel them and freeze them, for up to a year.

Caution: Do not confuse sweet chestnuts with poisonous horse chestnuts (conkers). Sweet chestnuts sit two or three together in a husk covered in fine, long spines, are flat on one side and have a pointed tip with a tuft of hairs; conkers usually sit alone in a husk with a few short, thick spines and are round and smooth. Always score the shell before roasting or boiling, or they will burst. Wear gloves when gathering. Throw away chestnuts with holes and any that float. Never eat anything you have not identified with certainty.

Eating and using is at your own risk: see the terms of use.

Recipes

• Roast chestnuts (Dish · 4 people · 45 min)
• Chestnut spread (crème de marrons) (Jam · ± 3 jars of 250 ml · 1 hr 30)
• Chestnut soup with leek and celery (Dish · 4 portions · 1 hr 15)
• Dried sweet chestnuts and chestnut flour (Dried · ± 350 g dried chestnuts · 1 hr + 8–12 hrs drying)

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Birds

Berries, seeds or insects as food, or a place to nest.

Did you know?

• Spread by the Romans. The roasted chestnuts at Christmas markets come from this tree.
• The wood is rich in tannins: that is why it rots slowly and is popular for posts and fencing.
• On old trees, the deep furrows in the bark spiral around the trunk.
• In poor mountain regions such as the Cévennes and Corsica, chestnut flour was a staple food for centuries; there the tree was called the ‘bread tree’.
• On Mount Etna in Sicily stands the ‘Hundred-Horse Chestnut’. Legend has it that a queen and a hundred knights once sheltered beneath it together from a storm.