Woolly willow

Woolly willow: how do you recognise it?

Habit

Slow-growing, rounded shrub 0.6–1 m tall and up to 1.5 m wide, with sturdy, gnarled branches.

Foliage

Broadly oval to round, 3–6 cm, thickly woolly and silvery-grey; the hairs are densest beneath.

Flower

Large, upright catkins in April–May, appearing with the leaves; the males are golden yellow, the females greenish.

Sex

Dioecious: male and female flowers are on different plants. The males are the showiest.

Roots

Fibrous and shallow: they need cool, evenly moist soil and dry out quickly.

Flowering: April–May · Plants: March–April and October–November · Pruning: May

Why grow it?

• Thick, silver-woolly foliage that stands out all season yet looks calm.
• Large yellow catkins in April–May: one of the finest willow flowers and early food for bees.
• Compact and low, suitable for a rock garden, a trough or the front of a border.
• Fully hardy, even in severe winters and in cold areas.
• Little pruning and little upkeep needed if the soil stays moist.

Woolly willow: where does it grow best?

• Sun to partial shade; in full sun it needs extra moisture, in partial shade it stays fresher.
• Humus-rich, well-drained soil: sand, loam or clay, acid to chalky.
• Normal to moist; keep the soil cool and evenly moist. It does not tolerate drought.
• Fully hardy and wind-tolerant; it suffers mainly in hot, dry corners.
• Allow 1–1.5 m per plant; in a rock garden at least 1 m.

Light

Sun and partial shade

Soil type

Sand, loam or clay

Acidity

Not fussy

Moisture

Normal or wet

Size

1 m tall, 1.5 m wide

Hardiness

Hardy (to -40 °C)

Goes well with

• Primula: An early spring bloomer that grows in the same cool, moist soil.
• Saxifrage: Small rosettes and flowers in the same rock garden.
• Cranesbill: A sturdy, flowering ground cover with blue or pink flowers.
• Fescue: A fine blue-grey grass that matches the silvery-grey foliage.

Woolly willow: when and how to plant it?

Plant in March–April and October–November.

1. Plant in October–November or March–April, when the soil is neither frozen nor waterlogged.
2. Dig a hole twice as wide as the root ball and mix in a few spades of compost.
3. Set the plant at the same depth as in its pot and firm the soil well.
4. Leave 1–1.5 m between plants.
5. Water in generously straight away and keep the soil constantly moist in the first year.
6. Spread a layer of compost, bark or fine gravel mulch around the base to keep the soil cool.

Care

Water

Keep the soil evenly moist, especially in summer and in the first year. It does not tolerate drought; in a pot, check daily in warm weather.

Feeding

Little needed. A little compost or organic feed in spring is enough.

Mulching

A layer of compost, bark or gravel keeps the roots cool and the soil moist.

Spent catkins

Leave them or snip them off after flowering to keep the shrub compact and tidy.

Pot

Use a large, wide pot with drainage holes and a humus-rich, well-drained compost.

Tip: Give it a cool, moist spot and lay a mulch around the base. Drought is its greatest enemy, however hardy it is.

Woolly willow: when to prune it?

Pruning months: May.

When: Straight after flowering, in May. Otherwise it hardly needs pruning.

How:

• Cut long, stray or dead branches back to a side shoot or bud.
• Keep it compact by shortening the branches by a third after flowering.
• Remove dead wood completely.
• Do not prune in winter: you would cut off next spring’s catkins.

Caution: Do not cut into old, bare wood: it regrows poorly from there. Stick to young, leafy branches.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Hardwood cuttings

From November to February, take 10–15 cm cuttings of ripened branches and push them half their length into moist soil. Willow cuttings usually root easily.

Semi-ripe cuttings

In July–August, take 8–10 cm cuttings of semi-ripe shoots in a sandy mix, under plastic or in a cold frame.

Seed

The seed stays viable for only a few days; sow it as soon as it is ripe. This is trickier than taking cuttings.

Woolly willow: how does it get through the winter?

Hardy to −40 °C.

• Fully hardy, down to about −40 °C: no protection is needed in Belgian winters.
• In a pot: stand the pot against a wall or near the house and wrap it in hessian so the roots do not freeze.
• Make sure the pot does not stand in water in winter, because waterlogged roots rot.

Diseases and pests

• Scorched leaf edges: A sign of drought or heat: water generously, mulch the soil and move it to a cooler spot.
• Aphids: Colonies on young shoots in spring. Wash them off with water or let ladybirds and hoverflies do the work.
• Rust: Orange pustules under the leaves in summer. Clear affected leaves and keep air moving between plants.
• Root rot: In soil that is too wet, especially in winter. Plant it higher or improve drainage with coarse sand.

Through the year

• March: Plant. Mulch.
• April: Flowering: yellow catkins for bees. Plant.
• May: Prune after flowering. Water.
• June: Water in dry weather.
• July: Water regularly, especially pots. Take semi-ripe cuttings.
• August: Take semi-ripe cuttings. Watch for drought.
• October: Plant. Leaves change colour.
• November: Plant. Take hardwood cuttings.
• December: Rest. Protect the pot from frost.

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Did you know?

• The species name lanata is Latin for ‘woolly’, after the thick hairs on the leaves.
• In the wild it is a rare mountain plant in Scotland, where it grows on a few rocky slopes.
• The dense white hairs give the foliage its silvery look, but they are also an adaptation to cold, windy places.