Snowmound spirea

Sun

Full sun for the most flowers; tolerates partial shade but flowers less heavily.

Water

Water regularly through the first growing season. Once established, water during prolonged dry spells; avoid persistently wet ground.

Soil

Average, well-drained soil, including clay that does not remain waterlogged; tolerates a broad range of soil pH.

Height

3-5 ft (0.9-1.5 m)

Spread

3-5 ft (0.9-1.5 m)

Flowers

Late spring to early summer; small white flowers in dense clusters along the branches.

Foliage

Small, oval to obovate, dark blue-green leaves; autumn colour is usually modest, sometimes yellow.

Growth

Moderate

Care needed

Low

• Pollinators
• Deer resistant
• Drought tolerant
• Cold hardy
• Wildlife
• Low allergen

Northern hemisphere months. In Australia, shift them by six.

Difficulty

Easy

Toughness

Very tough

Pick your zone, country, light and whether you have pets.

1. Planting day

   1.6 ft (0.5 m)

2. After 1 year

   2.1 ft (0.64 m)

3. After 2 years

   2.6 ft (0.78 m)

4. After 3 years

   3 ft (0.92 m)

5. After 5 years

   4 ft (1.2 m)

   full size

About 5 years to full size.

From a typical nursery size, at an average rate for this kind of plant. A rule of thumb, not a forecast.

Cats and dogs

Safe

Growth rate

Moderate

• Plant with the top of the root ball level with the surrounding soil and leave room for its full spread.
• Water deeply during the first growing season whenever the root zone starts to dry.
• Apply 2-3 in (5-8 cm) of organic mulch, keeping it clear of the stems.
• Add a thin layer of compost in spring; routine feeding is unnecessary in reasonably fertile soil.
• Avoid overhead watering where leaf diseases recur.

Pruning. Prune immediately after flowering because next year's flowers form on older wood. Remove up to one-third of the oldest stems at ground level and shorten wayward flowered shoots, rather than shearing the whole shrub.

Early spring

Refresh mulch and add a thin layer of compost if the soil is poor.

Spring

Plant container-grown shrubs while the soil is moist and workable; water thoroughly.

Late spring

Enjoy the flowers and check young shoots for aphids.

Early summer

Prune as soon as flowering finishes, removing selected old stems at the base.

Summer

Water newly planted shrubs during dry weather; take softwood cuttings if wanted.

Autumn

Plant where winters are mild and soil drains well; remove fallen leaves if leaf spot has been troublesome.

• Plant as an informal flowering hedge, allowing the arching branches to retain their natural shape.
• Use in a mixed shrub border with lilacs and later-flowering shrubs to extend seasonal interest.
• Set against a dark evergreen hedge so the white flowers stand out.
• Combine with catmint, hardy geraniums and spring bulbs for a loose cottage-garden border.
• Repeat along a broad path or lawn edge where mature branches will not obstruct passage.

Garden styles it suits: Cottage garden, English country, Traditional, White garden, Low-maintenance and Pollinator garden.

Plant it with: Catmint, Hardy geranium, Lady's mantle, Lilac, Daffodils and Salvia.

Wildlife: Flowers provide pollen and nectar for bees and other visiting insects. The branching growth offers some shelter for small birds.

• Aphids can cluster on soft shoots: wash off small colonies with water and encourage ladybirds and other predators.
• Powdery mildew may coat leaves in crowded or shaded conditions: improve airflow and avoid excessive nitrogen feeding.
• Leaf spots can cause blemished or prematurely falling leaves: collect affected fallen leaves and water at soil level.
• Poor flowering often follows winter pruning or heavy shade: prune only after flowering and provide a sunnier position.

Not known to be toxic to cats, dogs, horses or people; no part is recognized as a significant poisoning hazard. It is an ornamental plant, not a food plant.

• Vanhoutte spirea (Spiraea × vanhouttei)

  Usually grows substantially larger, with longer cascading branches and distinctly lobed leaves; Snowmound has smaller, mostly unlobed leaves.

• Bridal wreath spirea (Spiraea prunifolia)

  The commonly grown double-flowered form has tiny rose-like flowers on largely bare stems in early spring; Snowmound has single flowers clustered among developed leaves later in spring.

• Japanese spirea (Spiraea japonica)

  Usually bears pink flowers in broad, flatter clusters at shoot tips in summer and has more pointed, sharply toothed leaves; Snowmound flowers white along older branches earlier in the season.

The species name nipponica refers to Japan, while 'Snowmound' describes the shrub's mound-like mass of white flowers.

Propagation. Take softwood cuttings in early summer or semi-ripe cuttings later in summer. Layering a low branch also works; seed will not reliably reproduce the cultivar.

Accepted botanical name

Spiraea nipponica

Native range

Japan.

Sources: GBIF (CC BY 4.0) and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.