Narrow-leaved ash

Narrow-leaved ash: how do you recognise it?

Habit

Fast-growing deciduous tree about 20 m tall and 12 m wide, with a straight trunk and a round to oval crown.

Leaves

Compound with 7–13 narrow, pointed, toothed leaflets, light green and glossy. Wine red in autumn in ‘Raywood’.

Buds

Brown, whereas the buds of our common ash are black.

Flowers

Small, inconspicuous flowers in clusters in March–April, before the leaves open.

Fruit

Winged seeds in hanging clusters, in autumn.

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

Why grow it?

• Wine-red autumn colour in the form ‘Raywood’, one of the finest among ashes.
• Tolerates wet spells and warm summers, handy on soil that alternates between wet and dry.
• Fast growth and a round to oval crown: quickly a fine shade tree.
• Fine, lightly feathered foliage that lets plenty of light through.
• Very hardy and tough, even on heavier soil.

Narrow-leaved ash: where does it grow best?

• Full sun for the best autumn colour and vigorous growth.
• Almost any garden soil: sand, loam or clay, acid to chalky.
• Normal to wet; tolerates a temporarily high water table as well as warm, drier summers.
• Give it plenty of space: 8–10 m to the next tree and at least 10 m from buildings and pipes.
• Tolerates wind and city air well.

Light

Sun

Soil type

Sand, loam or clay

Acidity

Not fussy

Moisture

Normal or wet

Size

20 m tall, 12 m wide

Hardiness

Hardy (to -25 °C)

Goes well with

• Red-barked dogwood: Red stems in winter and a good match on moist soil.
• Guelder rose: Native shrub for moist soil with white flower heads and red berries.
• Meadowsweet: Frothy, creamy white plumes in moist spots beneath the tree.
• Snowdrop: Flowers beneath the still-bare tree in January and February.

Narrow-leaved ash: when and how to plant it?

Plant in March–April and October–December.

1. Plant in March–April or from October to December, when the soil is not frozen.
2. Dig a hole twice as wide as the root ball and just as deep. Loosen the sides and mix a little compost into the excavated soil.
3. Set the tree at the same depth as it stood in its pot or root ball: the root collar stays at soil level.
4. Fit a tree stake and tie the trunk loosely with a tree tie. Keep 8–10 m away from other trees.
5. Water in generously straight away, even if it is raining, so the soil settles firmly around the roots.
6. Spread a 5–8 cm layer of leaf mould or wood chips around the tree, keeping it clear of the trunk.

Care

Water

In the first two years, water generously every week in dry spells. After that it usually manages on its own.

Feeding

Usually not needed. On poor soil, give a little compost in March.

Mulching

A layer of leaf mould or wood chips keeps the soil moist and suppresses weeds.

Support

Keep the stake for the first 2–3 years and check the tie so it does not cut into the bark.

Self-sown seedlings

Seedlings sometimes appear under the tree. Pull them out in spring before they root deeply.

Tip: Plant it in an open, sunny spot where the autumn colour of ‘Raywood’ shows well, and keep it vigorous with mulch and water in the first years. Remove dead branches caused by ash dieback in February.

Narrow-leaved ash: when to prune it?

Pruning months: February.

When: In February, in frost-free weather, while the tree is dormant. A mature tree rarely needs pruning.

How:

• Shape young trees: choose one leading shoot and remove competing tops.
• Remove dead, broken and crossing branches, including those caused by ash dieback.
• Raise the crown gradually by cutting back low side branches.
• Leave work on large branches to a tree surgeon.

Caution: Do not cut thick branches without expert advice: large pruning wounds heal slowly.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Seed

Sow the winged seeds outdoors in autumn. They need cold to germinate and sometimes lie dormant for one or two winters. Seedlings are not always identical to the parent tree.

Grafting

Selections such as ‘Raywood’ are grafted onto a rootstock by the nursery. This is not easy at home.

Narrow-leaved ash: how does it get through the winter?

Hardy to −25 °C.

• Fully hardy, down to about −25 °C: no protection needed in Belgium.
• The leaves fall in autumn; leave them as natural mulch or take them to the compost heap.
• On young trees, check after a storm that the stake and tie are still secure.

Diseases and pests

• Ash dieback: A fungal disease: leaves wilt, shoots die and the crown thins. Remove dead branches and keep the tree vigorous; if in doubt, ask a tree surgeon for advice.
• Leaf spot: Brown spots on the leaves and early leaf fall in wet springs. Clear away fallen leaves; the tree usually recovers by itself.
• Aphids and honeydew: Sticky leaves and black sooty mould in summer. Usually harmless; ladybirds often clear them.
• Branch breakage: Branches can break in a severe storm or under wet snow. Good formative pruning in youth prevents this.

Through the year

• February: Prune: formative pruning of young trees and dead branches.
• March: Flowering before the leaves. Plant.
• April: Flowering. Plant. Check the stake.
• May: The leaves open. Water young trees in dry weather.
• June: Water young trees in dry weather.
• July: Water young trees in dry weather.
• September: Seed clusters ripen.
• October: Autumn colour, wine red in ‘Raywood’. Plant.
• November: Plant. Leave the leaves or clear them away.
• December: Plant in frost-free weather.

Did you know?

• In southern Europe the narrow-leaved ash often grows along rivers and in woods that flood regularly.
• The cultivar ‘Raywood’ is called claret ash in English, after its wine-red autumn colour.
• You can recognise the narrow-leaved ash by its brown buds; in our common ash they are black.