False spiraea

False spiraea: how do you recognise it?

Habit

Broad, dense shrub 1.5–2 m tall and up to 3 m wide, with upright stems and many suckers.

Foliage

Pinnate, 15–30 cm long, with 13–25 narrow, sharply toothed leaflets; fresh green, yellow-green in autumn.

Flower

Large, upright panicles of 15–25 cm, creamy white and lightly scented, in July–August.

Fruit

Small, dry fruits that turn brown in autumn and are not very showy.

Roots

Dense, fibrous and suckering: they produce plenty of suckers and spread quickly.

Flowering: July–August · Plants: March–April and October–November · Pruning: March

Why grow it?

• Large white flower plumes in July–August, a summer display rich in nectar and pollen for bees and other insects.
• Handsome, pinnate foliage that emerges early in spring.
• Very hardy, to about −40 °C, and easy in almost any garden soil.
• Flowers on new wood, so a hard pruning costs no flowers.
• Handy for quickly filling a large, awkward corner, a bank or a natural hedge.

False spiraea: where does it grow best?

• Sun to partial shade; in sun it flowers most freely, in partial shade it stays fresher.
• Almost any garden soil: sand, loam, clay or peat, acid to chalky.
• Normal to moist; it likes regular moisture but also tolerates temporary drought.
• Very hardy and wind-tolerant; ideal for an open, windy site.
• Allow 2–3 m per plant; in a wide hedge, 1.5 m.

Light

Sun and partial shade

Soil type

Sand, loam, clay or peat

Acidity

Not fussy

Moisture

Normal or wet

Size

2 m tall, 3 m wide

Hardiness

Hardy (to -40 °C)

Goes well with

• Panicle hydrangea: Another large shrub with white plumes, in the same sun or partial shade.
• Daylily: A robust perennial that holds its own beside the shrub.
• Guelder rose: Together in a mixed hedge with flowers and berries.
• Rudbeckia: Yellow flowers that carry on in late summer.

False 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 2–3 m between plants, and at least 1–2 m from small plants it could overrun.
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. Consider a root barrier if it must not spread.

Care

Water

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

Feeding

Little needed. A layer of compost in spring is enough.

Mulching

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

Suckers

Dig out or mow off suckers every spring and autumn where the shrub must not spread.

Spent plumes

Leave them until the March pruning; they stay slightly decorative in autumn.

Tip: Plant it where it can spread, or use a root barrier at least 40 cm deep. A yearly round with the spade keeps the suckers under control.

False spiraea: when to prune it?

Pruning months: March.

When: In March, before it leafs out. One pruning a year is enough.

How:

• Every year, remove a third of the oldest stems right at the base.
• Or cut the whole shrub back every 3–4 years to 30–50 cm above the ground; it regrows vigorously.
• Remove dead, damaged and weak stems.
• Dig out or cut off suckers where the shrub must not spread.

Caution: It flowers on new wood, so a hard pruning in March costs no flowers. Do not prune in summer: you would cut off the flowering shoots.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Suckers

In October or March, separate a rooted sucker from the parent plant and replant it straight away elsewhere. This is the easiest method.

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.

Seed

Sow in spring outdoors or in a tray; the seed is very fine. This is slower than taking suckers.

False spiraea: how does it get through the winter?

Hardy to −40 °C.

• Very hardy, down to about −40 °C: no protection is needed in Belgian winters.
• Leave the dry plumes until the March pruning; they give structure to the winter garden.
• It is less suited to a pot because it grows large and spreads; plant it in the open ground instead.

Diseases and pests

• Too many suckers: It spreads quickly. Dig out suckers every year or plant it where it can roam freely.
• Aphids: Colonies on young shoots in spring. Wash them off with water or let ladybirds and hoverflies do the work.
• Powdery mildew: White powder on the leaves in dry, still spells. Keep the shrub airy and water in dry weather.
• Brown leaf edges: A sign of drought or heat: water generously and mulch the soil.

Through the year

• March: Prune: remove a third of the old stems. Apply compost.
• April: Plant. Dig out suckers. Mulch.
• May: Watch for aphids. Water young plants.
• June: Water in dry weather. Remove suckers.
• July: Flowering begins: white plumes.
• August: Full flower. Water in dry weather.
• September: Plumes change colour. Remove suckers.
• October: Plant. Dig out suckers.
• November: Plant. Clear fallen leaves.
• December: Rest. The dry plumes give structure.

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Did you know?

• The name Sorbaria refers to Sorbus, the rowan: the pinnate foliage closely resembles that of the rowan.
• The shrub leafs out early in spring and is one of the first to carry fresh green foliage.
• In its homeland it grows on riverbanks and in open woods and tolerates very severe winters.