Angervo (Spiraea x billardii)

• Type: deciduous shrub, summer-flowering spiraea
• Botanical name: Spiraea × billardii (S. douglasii × S. salicifolia)
• Height and spread: 1.5–2 m / 1.5–2 m
• Flowering: June–August; bright pink narrow panicles up to 20 cm
• Foliage: green, greyish beneath; yellow in autumn
• Light: sun to part shade
• Soil: loose, moderately moist, well-drained; pH 5–8
• Hardiness: USDA 4–5, no winter cover needed in Estonia
• Pruning: early spring – flowers on current-year shoots
• Use: tall hedges, back of borders, banks, parks, bee plant
• Size: potted plant

Planting. Spiraea × billardii flowers best in sun but also grows well in part shade. The soil should be loose, moderately moist and free-draining, from slightly acid to slightly alkaline; very chalky soil can cause leaf chlorosis. For a hedge plant 2 per running metre, for groups 1–1.2 m apart. Container plants can go in from April to October.

Watering and feeding. Water once a week in the first year, 10 L per plant, more often in heat; established shrubs need water only in long droughts. Feed in spring with a balanced fertiliser; if the leaves yellow, give an iron chelate. Mulch to keep moisture in.

Care. Spiraea × billardii flowers on the current year's shoots, so prune it in early spring: shorten stems by a third to a half to strong buds and remove stems older than 4–5 years at the base. Cut off faded plumes to keep the shrub tidy and encourage extra flowers. Remove unwanted suckers if the shrub must not spread. No winter protection is needed in Estonia.

Gardener's tip. Thanks to its suckers, Spiraea × billardii quickly forms a dense wall – one of the best spiraeas for a tall flowering hedge along a fence. If you need a firm boundary, sink a root barrier 25–30 cm deep around the planting.