Spiraea

Spiraea: how do you recognise it?

Habit

Densely branched shrub of about 1.5 m tall and wide, with slender, arching, drooping branches.

Foliage

Narrow, lance-shaped, 2–4 cm; grey-green, paler and softly hairy beneath. Yellow in autumn.

Flower

Small white flowers in dense clusters along the whole branch, in April–May; they are borne on last year’s wood.

Colour

Pure white against grey-green leaves: in flower the shrub looks covered in snow.

Roots

Fibrous and shallow: easy to move; sometimes forms a few suckers.

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

Why grow it?

• Very rich white flowering in April–May, earlier than most other spiraeas.
• Arching branches and fine grey-green foliage give a light, airy look.
• The open little flowers are a source of nectar and pollen for bees and hoverflies in spring.
• Fully hardy, easy and suitable for almost any garden soil.
• Low maintenance: one prune after flowering is enough.

Spiraea: where does it grow best?

• Sun to partial shade; in sun it flowers most freely.
• Ordinary, well-drained garden soil: sand, loam or clay, acid to chalky.
• Normally moist; it tolerates temporary drought, but not permanently wet feet.
• Fully hardy and wind-tolerant; no special protection needed.
• Allow 1.2–1.5 m per plant; for an informal hedge, 80–100 cm.

Light

Sun and partial shade

Soil type

Sand, loam or clay

Acidity

Not fussy

Moisture

Normal

Size

1.5 m tall, 1.5 m wide

Hardiness

Hardy (to -30 °C)

Goes well with

• Forget-me-not: Blue flowers beneath the white branches, at the same time.
• Tulip: A spring bloomer that adds colour under the shrub at the same time as the spiraea.
• Weigela: Follows in May–June with pink flowers, so the flowering carries on.
• Lilac: Flowers after the spiraea, so spring stays in bloom.
• Daffodil: Yellow flowers at the foot, alongside the first flowers.

Spiraea: 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 1.2–1.5 m between plants, or 80–100 cm for a hedge.
5. Water in generously straight away and keep the soil moist in the first year.
6. Spread a layer of compost or bark mulch around the base.

Care

Water

In the first year, water generously once a week in dry weather. After that it copes, except in long dry summers.

Feeding

In spring, a spade of compost or organic feed for flowering shrubs. Do not feed after July.

Mulching

A layer of compost or bark in March keeps the soil moist and weed-free.

Spent flowers

No need to remove them one by one; pruning after flowering takes them away.

Suckers

Dig out the few suckers it forms where it must not spread.

Tip: Prune straight after flowering, never in winter: that keeps next year’s flowers. Every few years, remove a few old branches right at the base.

Spiraea: when to prune it?

Pruning months: May.

When: Straight after flowering, in May. It flowers on last year’s wood.

How:

• Shorten the flowered branches by a third or back to a strong side shoot.
• Every 2–3 years, remove a quarter of the oldest branches at the base to keep the shrub young.
• Remove dead, damaged and crossing branches completely.
• An old, bare shrub can be cut back to 20–30 cm above the ground after flowering; it will regrow.

Caution: Do not prune in winter or early spring: you would cut off this year’s flower buds.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Semi-ripe cuttings

In June–August, take 8–10 cm cuttings of semi-ripe shoots, strip the lower leaves, and insert them in a sandy mix under plastic or in a cold frame. Rooting takes a few weeks.

Hardwood cuttings

From November to February, take 20–25 cm cuttings of ripened branches and push them half their length into the soil. They usually succeed well.

Suckers

In October or March, separate a rooted sucker from the parent plant and replant it elsewhere.

Spiraea: how does it get through the winter?

Hardy to −30 °C.

• Fully hardy, down to about −30 °C: no protection is needed in Belgian winters.
• The bare, fine branches stay neat in winter and give structure to the garden.
• In a pot: stand the pot against a wall and wrap it in hessian so the roots do not freeze.

Diseases and pests

• Poor flowering: Usually pruned too late or too hard, or too much shade. Prune straight after flowering and give it more light.
• Old, bare shrub: The inside becomes bare if it is not renewed. Take out old branches every few years and cut it back if necessary.
• Aphids: Colonies on young shoots in May. Wash them off with water or let ladybirds and hoverflies do the work.
• Leaf spot and mildew: Rare; mainly in drought or damp, still places. Keep it airy and clear fallen leaves.

Through the year

• March: Plant. Apply compost or feed. Mulch.
• April: First flowers: white snow on the branches. Plant.
• May: Full flower. Prune straight after flowering.
• June: Take semi-ripe cuttings. Water in dry weather.
• July: Take cuttings. Water in dry weather.
• August: Water in dry weather.
• October: Plant. Yellow autumn colour.
• November: Plant. Take hardwood cuttings. Clear fallen leaves.
• December: Rest.

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Did you know?

• The species name cinerea is Latin for ‘ash-grey’, after the grey-green foliage.
• The name Spiraea comes from the Greek speira, ‘wreath’, because the flexible twigs were once used for making wreaths.
• The open little flowers are easily reached by short-tongued insects such as hoverflies and many bees.