Spiraea – Popular Shrubs for the Garden
This is another biggish group of shrubs, with about fifty kinds available, though for the normal shrub garden the selection can be limited to a few. Even these are varied in height, habit and flower colour.
The most familiar kind is the hybrid Spiraea X arguta, known to many gardeners as the Bridal Wreath, a shrub eventually about 6 feet tall, with slender arching stems, wreathed in April and May with multitudes of tiny white. To ensure that the shrub has ample opportunity to produce the long new shoots on which the flowers appear, it is necessary to prune after flowering at about the end of May, cutting back hard the old stems that have flowered.
The equally popular Spiraea X bumalda ‘Anthony Waterer’ must be treated even more drastically for in April it should be cut practically down to the ground. It will then produce masses of stems, about 2 feet tall, which, in late summer will bear flattish heads of crimson flowers. If these are cut off after they have faded, more may be produced well into September. Those who like variegated foliage should note that very often the leaves of this shrub are variegated with pink and creamy-white.
Spiraea thunbergii starts the season by flowering in late March or early April. In habit and in flower it is not unlike Spiraea X arguta, but it is not so tall, reaching 4 feet. It should be pruned in the same way. Spiraea X vanhouttei, again similar in habit and flower to Spiraea X arguta, flowers in June, but is taller, growing to about 7-8 feet.
All these spiraeas, flowering as they do on new growth, benefit from reasonably generous treatment and annual. They have no particular requirements but do better if the soil is well dug and enriched with compost at planting time and if it is given an annual mulch of compost, rotted manure or hop manure.
See: more varieties of popular shrubs