Plant of the Month: April

Spiraea 'Arguta' AGM Common name: Bridal wreath, foam of May Family: Rosaceae Vital statistics Height and spread: Up to 2.5m (8ft) tall and wide Form: Deciduous shrub with arching stems Soil: Fertile, moist, well-drained soil. Aspect: Full sun Hardiness: Fully hardy

Spiraea 'Arguta'@ Harlow Carr

We have a number of plantings. The first is located directly below the Restaurant, on the path edge adjacent to the Tarn Gulley. This shrub can be seen as the visitor walks towards the flower trials area.

Another planting is located in the main borders, as the visitor walks up the borders form the streamside. And shrubs can be seen in the second bed along on the left hand side.

Spiraea

This is a genus of about 80 species of deciduous or semi-evergreen shrubs.  They grow in rocky places, thickets, woodlands, woodland margins and riverbanks.  Their wide distribution throughout the northern temperate regions extends through Europe, Asia and North America including Mexico.

They are cultivated mainly for their terminal, umbel-like racemes of flowers.  These are small and mainly saucer or bowl-shaped, white, yellow, pink or purple flowers.  Each flower may be 0.5-1cm across, or sometimes a little larger.  They cover the shrub when borne in spring or summer.

Compact spiraeas are ideal for rock gardens.  Low growing variants of S. japonica make good ground cover plants.  Taller spiraeas can be used for informal hedges.

The name Spiraea is derived from the Greek word speiraia, meaning a plant used for garlands.

Spiraea 'Arguta'

Spiraea 'Arguta' has an interesting parentage.  It is a seedling of S. x multifora and S. thunbergii.

And S. x multifora is thought to be a cross of S. hypericifolia and S. crenata. 

It is a dense, rounded, deciduous shrub with slender, arching stems that are twiggy and covered with down.  The leaves are lance-shaped, narrowly oblong, toothed and bright green, up to 4cm (1½in) long.  The saucer-shaped flowers are borne in the spring in terminal corymbs.  They reach 6cm (2.5in) across on short, leafy, lateral branches of the previous year's growth. 

The way in which the tiny white flowers smother the arching stems has given rise to its common names of bridal wreath and foam of May.

It is said to be the most beautiful of spring flowering spiraeas, never failing to produce a mass of flowers.

AGM

The RHS Floral B Committee awarded Spiraea 'Arguta' an Award of Garden Merit.

Cultivation

Grow spiraeas in fertile, moist, well-drained soil in an open sunny position.  They are best grown in larger gardens as groups of threes or fives and can also be grown as a hedge.

For those that flower in the spring, on the previous season's wood like S. 'Arguta', pruning is essential and carried out annually out after flowering. Thin out the older flowering stems, either from ground level or to where good strong shoots are growing further up the stems.

Summer flowering spiraeas, which flower on the current season's wood such as S. x billiardii and S. douglasii, can be pruned in early spring.

Spiraeas are generally free from pests and diseases.

Propagation

Take greenwood cuttings in the summer.  Divide suckering species such as S. x billiardii and S. douglasii in late autumn or early spring.  Or increase by layering.