Indian horse chestnut

Indian horse chestnut: how do you recognise it?

Habit

Broad, rounded crown 18 m tall and 12 m wide; fairly fast-growing when young.

Leaves

Palmate, made up of 5–9 glossy leaflets of 10–25 cm; bronze-pink when unfolding, yellow to orange in autumn.

Flower

Upright candles of 20–30 cm, white to pale pink with yellow and pink markings, in June–July.

Fruit

Smooth, pear-shaped capsule holding 1–3 glossy brown seeds (conkers) that fall in September–October.

Roots

Deep and widely branching: the tree needs a lot of space.

Flowering: June–July · Plants: March–April and October–December · Pruning: January–February

Why grow it?

• Flowers late, in June–July, a month after the common horse chestnut, and is a rich source of nectar and pollen for bees and bumblebees.
• Beautiful foliage: bronze-pink when unfolding, glossy green in summer and yellow in autumn.
• Suffers far less from the horse chestnut leaf miner than the common horse chestnut.
• A sturdy shade tree and eye-catcher for a large garden or park.
• Thrives on almost any soil and is fully hardy.

Indian horse chestnut: where does it grow best?

• Sun or partial shade; it flowers most richly in sun.
• Almost any soil: sand, loam or clay, acid to chalky, though best deep, humus-rich and moisture-retentive.
• Normally moist; it dislikes permanently wet or very dry soil.
• Allow plenty of space: at least 10–12 m of clear room all round, far from houses, drains and paving.
• Sheltered from strong wind, especially when young.

Light

Sun and partial shade

Soil type

Sand, loam or clay

Acidity

Not fussy

Moisture

Normal

Size

18 m tall, 12 m wide

Hardiness

Hardy (to -23 °C)

Goes well with

• Snowdrop: Flowers early in spring under the tree, before the leaves unfold.
• Bluebell: A blue carpet in April–May under the still-bare crown.
• Wood anemone: Flowers in spring and tolerates the shade of the tree.
• Ferns: Suit the dry shade under the dense crown.

Indian horse chestnut: when and how to plant it?

Plant in March–April and October–December.

1. Plant in October–December or March–April, when the soil is neither frozen nor too wet. Bare-root trees in November–March.
2. Dig a hole two to three times as wide as the root ball and loosen the sides and bottom.
3. Set the tree at the same depth as in the pot or nursery and backfill with the soil you dug out, without fertiliser.
4. Drive in a sturdy stake and tie the trunk loosely with a tree tie; check it every year.
5. Water thoroughly when planting and then in dry weather for 2–3 summers.
6. Lay a mulch ring 5–8 cm deep of compost or wood chips, kept away from the trunk.

Care

Water

For the first 2–3 years, water thoroughly 1–2 times a week during long dry spells. An established tree usually looks after itself.

Feeding

Usually not needed. A thin layer of compost in spring is enough on poor soil.

Mulching

A mulch ring keeps the soil moist and weed-free; keep the trunk itself clear.

Support

Young trees get a stake for the first 2–3 years, which you then remove.

Leaves and fruit

Clear fallen leaves and conkers in autumn: it limits leaf diseases and stops children or pets picking them up.

Tip: It flowers only in June–July, a month later than the common horse chestnut, and suffers little from the leaf miner. Note: the conkers are poisonous.

Indian horse chestnut: when to prune it?

Pruning months: January–February.

When: As little as possible. If needed between January and February, in the dormant season, in dry, frost-free weather.

How:

• Remove dead, damaged and crossing branches.
• Give a young tree a sound framework: keep one leading stem and remove competing tops.
• Saw large branches off in three steps, just outside the branch collar, so that the wound can heal.
• Leave felling or crown reduction of large trees to a tree surgeon.

Caution: Do not prune in wet weather and avoid unnecessary wounds: horse chestnuts are susceptible to bleeding canker.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Sowing

Sow fresh conkers in October–November directly outdoors, 5 cm deep, protected from mice and squirrels. They germinate in spring; the young trees grow slowly. They do not always resemble the parent tree.

Grafting

Cultivars such as ‘Sydney Pearce’ are grafted by nurseries; this is not a job for the ordinary gardener.

Indian horse chestnut: how does it get through the winter?

Hardy to −23 °C.

• Fully hardy, down to about −23 °C: no protection is needed, even in harsh Belgian winters.
• Young trees: leave the stake in place and add an extra layer of mulch around the base in the first year.
• Clear fallen leaves and conkers; do not leave a thick mat of wet leaves around the trunk.

Diseases and pests

• Horse chestnut leaf miner: Brown blotches in the leaves in summer. This species suffers much less than the common horse chestnut. Clear fallen leaves in autumn and compost or remove them.
• Bleeding canker: Reddish-brown, slimy patches on the bark and dying branches. There is no simple cure; cut affected branches off in dry weather and call a tree surgeon if the trunk is affected.
• Leaf blotch: Brown patches with a yellow edge on the leaves in wet summers. Usually harmless; clear the fallen leaves.
• Drought damage: Brown, curled leaf edges in hot summers. Water young trees enough and mulch around the base.

Through the year

• January: Prune if needed (dead wood). Check young trees after wind and frost.
• February: Prune if needed. Check the tie and stake.
• March: Plant (container trees). Mulch.
• April: Plant. Water the young tree in dry weather. Leaves unfold bronze-pink.
• May: Leaves unfold. Watch for drought in young trees.
• June: Flowering begins. Bees and bumblebees on the flowers.
• July: Full flower. Water young trees in dry weather.
• August: Watch for leaf blotch and drought damage.
• September: First conkers fall. Autumn colour begins.
• October: Collect conkers and sow if you like. Clear fallen leaves. Plant.
• November: Plant (bare-root too). Clear the last leaves.
• December: Plant if the soil is open. Rest.

Edible and useful

Not edible. Buckeyes and horse chestnuts are poisonous in all their parts, especially the shiny brown seeds: they cause vomiting, stomach ache and diarrhoea. Children take them for sweet chestnuts, but those come two or three to a husk covered in fine, sharp spines, with one flat side and a pointed tip ending in a little tuft; these seeds sit in a smooth husk, are round and have a large pale patch. Dogs that chew them become ill, and a swallowed seed can block the gut. Pick up the seeds where children or animals play, and do not plant them next to a field with horses or livestock. If any is swallowed, call a poison centre (in Belgium 070 245 245) or your doctor at once.

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Did you know?

• The horse chestnut is not related to the edible sweet chestnut: Aesculus belongs to the soapberry family, Castanea to the beech family.
• The fruit husks are smooth and without spines, unlike those of the common horse chestnut.
• The foliage consists of 5–9 leaflets forming an open hand together; when unfolding they are bronze-pink.