Crack willow

Crack willow: how do you recognise it?

Habit

Tree of 10–20 m with a broad crown about 12 m across; usually pollarded, with a short, thick trunk and a head of straight branches.

Leaves

Alternate, 7–15 cm, lance-shaped with a long pointed tip, coarsely and somewhat irregularly toothed; glossy green above, blue-green and (almost) hairless below.

Bark

Grey and deeply furrowed in a network pattern. The glossy, yellowish-brown twigs break off easily at the base.

Flowers

Slender catkins in April, together with the leaves; male and female on separate trees.

Fruit

Fluffy seeds in May–June.

Difference from white willow

White willow has a smaller, silvery-hairy leaf with finer teeth; its twigs do not break off so easily.

Difference from bay willow

Bay willow has a broader, very glossy leaf that smells of bay, and catkins only in May–June.

Flowering: April · Pruning: November–March

Identify by feature: Long, narrow leaves

Looks like it, but isn’t

• White willow Salix alba: smaller, silvery-hairy leaf with finer teeth; the twigs do not break off so easily. Difference from white willow
• Bay willow Salix pentandra: broader, very glossy leaf that smells of bay, and catkins only in May–June. Difference from bay willow

Why grow it?

• A true pollard willow: every pollarding yields posts, weaving material and firewood.
• Old, hollow pollard willows provide nest sites for little owls and tits; the catkins are early food for bees.
• Child’s play to propagate: a branch pushed into the ground (a ‘set’) roots easily.
• Copes with wet feet and flooding, and holds banks together.

Crack willow: where does it grow best?

• Full sun.
• Moist to wet soil by a ditch, stream or pond; any soil type, and it tolerates flooding.
• As a free-standing tree (10–20 m, crown 12 m) only for a meadow, a bank or a very large garden; as a pollard it takes up far less room.
• Keep even a pollard away from the house, sewers and drains: the roots seek out water.

Light

Full sun

Legal basis

Any garden soil

Moisture

Moist to wet

Size

15 m tall, 12 m wide

Hardiness

Throughout Belgium, no protection needed

Goes well with

• White willow: The other classic pollard willow: a row of both species turns green and silvery grey.
• Alder: Together they hold the bank of a stream or ditch.
• Osier: A shrubby willow with supple rods for finer weaving than the pollard branches allow.

Good and bad companions

Goes well with

• Tolerate the shade under this tree: oregon grape, rhododendron, oleaster, japanese skimmia, garden privet, camellia, laurustinus, box-leaved honeysuckle

Crack willow: when and how to plant it?

1. A pollard willow is planted as a ‘set’: a straight, fresh branch about 2.5 m long and as thick as a wrist, sawn from another pollard in winter.
2. Make a hole with a stake or crowbar and push the set about 50 cm deep, buds pointing upwards; firm the soil well.
3. In a meadow, protect sets from cows, horses and sheep: they eat the bark and young shoots.
4. Plant from November to March; on drier soil a set needs watering in dry spells during the first year.

Care

Pollarding

Cut off all the branches every 3–7 years (see pruning).

Trunk shoots

On a young pollard, remove the shoots on the trunk during the winter prune, so that only the head grows.

Watering

Never needed on wet soil; young sets on drier soil in dry spells during the first year.

Free-standing trees

Have a free-grown crack willow next to a path or road checked regularly: its branches break easily.

Tip: Ask for sets when willows are being pollarded near you, from a neighbour, a nature group or the local council: a fresh 2.5 m branch is free planting stock, and within a few years you will have a pollard of your own.

Crack willow: when to prune it?

Pruning months: November–March.

When: Pollard in winter (November–March), preferably not when it is freezing.

How:

• Every 3–7 years cut all the branches off just above the head. If you wait too long, the head splits under the weight of the heavy branches.
• Saw off thick branches in two stages: first a little higher up, then just above the head, so that the bark doesn’t tear.
• Let a new set form a head in its first few years; after that, always pollard it at the same height.

Caution: Don’t leave cut branches lying on wet ground unless you want them to root there: crack willow branches take root very easily.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Cuttings and sets

In winter, push fresh twigs of 20–30 cm or sets into moist soil: they root readily.

Living willow work

Fresh branches pushed into the ground and woven together grow into a living willow screen.

Crack willow: how does it get through the winter?

Hardy throughout Belgium: no protection needed.

• Fully hardy, and it copes well with winter flooding.
• Winter is pollarding season: choose a day without hard frost.

Diseases and pests

• Splitting head or branches: Pollarding left too late, or a tree grown freely: the heavy branches split off. Pollard on time, every 3–7 years.
• Blue willow beetle: Small blue beetles and their larvae eat the leaves. Harmless to a pollard.
• Goat moth caterpillar: The fat, red caterpillar of the goat moth bores tunnels in the trunk; sawdust and a vinegary smell give it away. Old pollards often live with it for years.
• Red beans on the leaves: Galls caused by a sawfly. Harmless: no action needed.

Through the year

• January: Pollarding (not in hard frost); cut sets.
• February: Pollarding; plant sets and cuttings.
• March: Last month for pollarding and planting sets.
• April: Catkins, together with the leaves: food for bees.
• June: Fluffy seeds drift about.
• July: Water young sets on drier soil.
• November: Pollarding season begins.
• December: Pollarding; sort branches for posts, weaving and firewood.

What can you use it for?

Garden and landscape

Often grown as a pollard along streams and ditches; a branch pushed into the ground (a ‘set’) roots easily.

For wildlife

Old, hollow pollard willows provide nest sites for little owls and tits; the catkins are early food for bees.

Also used for

Pollard branches provide posts, weaving material and firewood.

Did you know?

• Broken-off twigs drift downstream and take root where they wash up: that is how it spreads along rivers.
• The name fragilis means ‘brittle’, just like the ‘crack’ in crack willow.
• Crack willow is a hybrid: according to recent research, between white willow and a willow from the Black Sea region (Salix euxina).