Spiraea, commonly mis-spelt as spirea, are quick-growing deciduous shrubs grown mainly for their attractive flowers in spring or summer. Flowers are borne in profusion and in heads or clusters made up of many tiny blooms, which are white, pink or purple in colour. White-flowered spiraeas are sometimes known as ‘bridal wreath’.
Some varieties of spiraea also have colourful golden foliage which is at its brightest in spring when the leaves are young, maturing to yellow-green in summer.
Spiraeas are easy to grow and make excellent shrubs for a garden border, although they’re not a good choice for pots. Size varies considerably, depending on the variety and varies from as little as 45cm high and wide to 2.4m, so matching the plant variety size to its site is clearly important. Spiraeas are hardy and easy to grow.
How to grow spiraea
Plant spiraea when dormant, in garden borders. Mulch and feed annually and prune, if necessary, after flowering. Mature overgrown spiraeas can be rejuvenated by selective renovation pruning. Propagate spiraeas by cuttings in mid to late summer.
Growing spiraea: jump links
- Planting spiraea
- Caring for spiraea
- Propagating spiraea
- Growing spiraea: problem-solving
- Where to buy spiraea
- Types of spiraea to grow
Where to grow spiraea
Grow spiraea in garden borders in fertile, well-drained soil. Improve poor soils by adding well-rotted organic matter before planting. Depending on plant size, site your spiraea towards the back, middle or front of the border. The smallest spiraeas give the best effect if planted in a group of three. Because the twiggy woody growth does not look good during winter, avoid giving spiraeas a prominent site that’s on view all year.
How to plant spiraea
Spiraeas are hardy and are ideally planted in autumn, during mild spells in winter, or early spring. Planting can be done while in full growth in spring or summer, as long as plants are watered regularly. Plant with the top of the rootball at the same depth as the soil level, firm in, and water well to settle the soil around the roots.
How to care for spiraea
Once established, spiraea needs little attention apart from pruning. Spiraea is hardy and doesn’t require any special winter care. As with all border shrubs, a spring mulch of well-rotted organic matter will keep the soil – and therefore the plant – in good condition. Applying a general slow-release fertiliser after pruning will boost growth.
How to cut back spring-flowering spiraea
Prune immediately after flowering, as next year’s flowers will be borne on shoots produced in summer. Cut back the flowered shoots to strong new growth below, pruning to a pair of buds.
How to cut back late summer-flowering spiraea
Species such as Spiraea japonica, which bloom in late summer, do so on growth produced the same year. Cut back all growth in early spring to around 30cm from the ground. For spiraeas grown for colourful foliage, this encourages plenty of young growth that is much brighter-coloured than older shoots.
Renovation pruning of older shrubs
Spiraeas tend to develop dense, twiggy growth that becomes congested in the centre, so the shrub grows large with fresh growth on the outside only. After several years, take out about a quarter of the oldest stems near to the ground, which lets light and air through the centre and encourages fresh new growth to develop.
How to propagate spiraea
Take semi-ripe cuttings of non-flowering shoots in mid to late summer. Some spiraeas form spreading clumps and produce shoots on the outer part of the clump (called suckers) which form roots at the base: these can be detached and planted separately.
Growing spiraea: problem solving
Spiraea is a trouble-free shrub to grow as long as it’s planted in good soil. In poor soil that’s liable to dry out, powdery mildew may appear on the leaves.
Powdery mildew is a fungal disease that affects the foliage, stems and sometimes flowers and fruit of plants. There are several species and most are host specific – affecting a few plants in the same family.
Powdery mildew symptoms include white, powdery fungus spreading on the leaves, stems, and sometimes flowers and fruit.
The best way to prevent powdery mildew forming is to grow your spiraea in full sun and to water regularly in dry weather. Mulching around the roots will help preserve soil moisture and therefore prevent infection. Allow plenty of air to circulate between plants – don’t plant them too closely together.
Spiraea varieties to grow
Spiraea betulifolia ‘Island’ – a low growing, compact, deciduous shrub with white flowers. Height x Spread: 100cm x 100cm.
Spiraea japonica ‘Magic Carpet’ – works well as ground cover, low hedging and can be used in pots. Pretty pink flowers. H x S: 60cm x 60cm
Spiraea x vanhouttei – exceptional autumn colour, with pure white flowers in summer. H x S: 180cm x 150cm
Spiraea x cinerea ‘Grefsheim’ – long pure white flower spikes against dark green leaves. H x S: 1.5m x 1.5m
Spiraea japonica ‘Anthony Waterer’ – Bright pink flowers against pink-tinged, green leaves. H x S: 2m x 1.5m