Swiss willow

Swiss willow: how do you recognise it?

Habit

Compact, low shrub 40–60 cm tall and wide, with short, creeping to upright branches.

Foliage

Small, elliptic to obovate, 2–4 cm; grey-green and softly hairy, silvery beneath.

Flower

Soft, silvery-grey catkins in April–May; those of male plants turn yellow with pollen afterwards.

Sex

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

Roots

Shallow to medium-deep and fibrous: they dry out quickly in dry summers.

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

Why grow it?

• Compact and low, ideal for a small garden, a rock garden or a large pot.
• Silvery-grey foliage that looks light and attractive all season.
• Soft, silvery catkins in April–May that feed bees early in the year.
• Fully hardy, so suitable even for cold areas.
• Little pruning and little upkeep needed.

Swiss willow: where does it grow best?

• Sun to partial shade; in full sun it stays compact but needs more moisture.
• Well-drained, humus-rich soil: sand, loam or clay, acid to chalky.
• Normal to moist; keep the soil cool and evenly moist, but not waterlogged in winter.
• Fully hardy; it likes a cool spot and suffers in hot, dry corners.
• Allow 50–60 cm per plant; in a group, 50 cm.

Light

Sun and partial shade

Soil type

Sand, loam or clay

Acidity

Not fussy

Moisture

Normal or wet

Size

0.6 m tall, 0.6 m wide

Hardiness

Hardy (to -35 °C)

Goes well with

• Saxifrage: Small rosettes and flowers in the same cool, moist rock garden.
• Primula: Flowers in spring at the same time as the catkins.
• Gentian: Blue flowers in the same mountain-garden setting.
• Stonecrop: A sturdy, low plant for the drier spots of the rock garden.
• Bellflower: Small blue flowers in summer among the silvery-grey foliage.

Swiss 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 too wet.
2. Dig a hole twice as wide as the root ball and mix in coarse sand or grit and compost for good drainage.
3. Set the plant at the same depth as in its pot and firm the soil well.
4. Leave 50–60 cm between plants.
5. Water in generously straight away and keep watering regularly through the first year.
6. Spread a layer of fine gravel or bark around the base to keep the soil cool.

Care

Water

Keep the soil regularly moist, especially in summer and in the first year. In a pot, check daily in warm weather.

Feeding

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

Mulching

A thin layer of fine gravel or bark 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 wide, shallow pot with drainage holes and a well-drained compost mixed with grit.

Tip: Give it a cool, slightly moist spot and use a layer of gravel as mulch. In a pot, water regularly and make sure there is good drainage.

Swiss 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 twigs 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 June–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.

Swiss willow: how does it get through the winter?

Hardy to −35 °C.

• Fully hardy, down to about −35 °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

• Shrivelling leaves: A sign of drought or heat: water generously and move it to a cooler or more sheltered 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: catkins for bees. Plant.
• May: Prune after flowering. Water.
• June: Water in dry weather. Take cuttings.
• July: Water regularly, especially pots.
• August: Take semi-ripe cuttings.
• October: Plant. Autumn: 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 helvetica refers to Helvetia, the old Latin name for Switzerland.
• Like almost all willows, it is dioecious: only the male plants carry the yellow pollen catkins.
• Mountain willows like this one grow at altitude and are often low and dense to survive wind and cold.