Caucasian wingnut

Caucasian wingnut: how do you recognise it?

Habit

Fast-growing, broad tree 20–25 m tall and 15–20 m wide, often multi-stemmed and suckering freely.

Leaves

Pinnate, 20–60 cm long, with 11–27 leaflets; dark green, yellow in autumn.

Flowers

Long, greenish catkins in May; the female ones hang in strings of 20–50 cm.

Fruit

Small nuts with two wings, in long hanging strings in summer.

Buds

Brown and hairy, without bud scales; a good identification clue in winter.

Roots

Wide-spreading, with many suckers that can come up far from the trunk.

Flowering: May · Plants: March–April and October–December

Why grow it?

• Grows fast and gives plenty of shade and a sturdy, landscape-scale tree within a few years.
• Thrives on wet or damp soil where many other big trees struggle.
• Unusual, long hanging strings of winged nuts in summer.
• Large, pinnate leaves with yellow autumn colour and a broad, gnarled crown full of character.
• Suitable for pond edges, stream banks and natural plantings in large gardens.

Caucasian wingnut: where does it grow best?

• Sun to half shade; it grows best with plenty of light.
• Deep, moist sandy, loamy or clay soil, acid to chalky; it tolerates temporary wetness and thrives beside water.
• Normal to wet; keep the soil adequately moist in dry summers, because it suffers on soil that is too dry.
• Allow 15–20 m of free space; do not plant it near houses, pipes or neighbours.

Light

Sun and partial shade

Soil type

Sand, loam or clay

Acidity

Not fussy

Moisture

Normal or wet

Size

25 m tall, 20 m wide

Hardiness

Hardy (to -25 °C)

Goes well with

• Alder: A native tree for wet soil, ideal for a damp, natural planting.
• Yellow flag iris: Keeps its feet in the water at the edge of a pond or ditch.
• Meadowsweet: Tall, fragrant plumes in a wet border.
• Marsh marigold: A yellow spring flower beside the water.

Caucasian wingnut: when and how to plant it?

Plant in March–April and October–December.

1. Plant in March–April or in October–December, as long as the soil is not frozen.
2. Dig a hole twice as wide as the rootball and just as deep. Loosen the sides and bottom with the spade.
3. Set the tree at the same depth as it stood in the nursery; the root collar should be level with the soil.
4. Backfill, firm lightly, tie the trunk to a stake and give it a generous watering.
5. Spread compost or bark around the base, not against the trunk. Plant it in an open spot where you can mow the suckers.

Care

Water

In the first years, water generously once a week in dry weather. On dry soil, also later in long dry summers.

Feeding

Usually not needed. On poor soil a little compost in spring is enough.

Mulching

A layer of bark or compost keeps the soil moist and suppresses weeds. Keep it away from the trunk.

Suckers

Mow or remove suckers regularly in summer; in a lawn they disappear by themselves with mowing.

Stake

A stake stays for 2–3 years; check that the tie is not cutting into the trunk.

Tip: Plant it only on a large, open plot with moist soil, preferably beside water. Mow the suckers regularly and the tree stays under control.

Caucasian wingnut: when to prune it?

When: It rarely needs pruning. Dead or damaged branches can be removed all year; for necessary pruning, summer is best.

How:

• Cut dead, broken or crossing branches back to the branch collar.
• Remove suckers by cutting them off with a piece of root or pulling them out, not just snipping them off.
• Keep one continuous leader and, if needed, thin a multi-stemmed tree to a few strong trunks.

Caution: Members of the walnut family can lose a lot of sap in spring: prune in summer rather than spring, and not too much at once.

Pruning calendar and basic rules

Propagation

Suckers

In autumn or winter, detach a sucker with roots and plant it elsewhere. This is the easiest and quickest method.

Seed

Sow fresh nuts outdoors in autumn, or chill them moist in the fridge for a few weeks and sow in spring. Seedlings grow fast.

Caucasian wingnut: how does it get through the winter?

Hardy to −25 °C.

• Hardy to about −25 °C: no protection is needed for mature trees in Flanders.
• It leafs out early: a late night frost can damage young shoots and leaves. Do not plant it in a frost pocket.
• A tree of this size does not belong in a pot: plant it in open ground only.

Diseases and pests

• Suckers: Many shoots around the tree, sometimes metres away. Mow them regularly or detach them with a piece of root.
• Late frost: Brown, wilted young shoots and leaves after a night frost in spring. The tree usually recovers and leafs out again; do not plant it in a frost pocket.
• Leaf scorch: Brown leaf edges in a dry summer on soil that is too dry. Give extra water and add a layer of mulch.
• Aphids: Sticky honeydew on and beneath the leaves. A large tree usually copes by itself; do not park a car or put a bench beneath it.

Through the year

• March: Plant. Remove dead branches. Give compost.
• April: Plant. The leaves unfurl; watch for night frost.
• May: Flowering with long catkins. Mow or detach suckers.
• June: Water in dry weather. Remove suckers.
• July: The fruit strings form. Water young trees.
• August: Water during prolonged drought. Necessary pruning.
• October: Plant. Yellow autumn colour. Detach suckers.
• November: Plant. Clear fallen leaves or leave them as mulch.
• December: Plant. Rest.

Did you know?

• The name Pterocarya comes from the Greek: pteron ‘wing’ and karyon ‘nut’. The species name fraxinifolia means ‘with ash-like leaves’.
• It belongs to the walnut family, like the walnut and the hickory.
• The hanging fruit strings can reach 20–50 cm and look like long chains of winged nuts.