Few shrubs are as spectacular in bloom as established plantings of Spiraea vanhouttei (Bridal Wreath Spirea). Not all of us have room for this magnificent bloomer, but breeders have worked diligently to develop smaller spirea with three-season interest. Two of my favorites are Spiraea ‘Magic Carpet’ and Spiraea ‘Little Princess’. Both plants are 2′-3′ (.6-1.0 m) high by 3′-4′ (1.0-1.2 m) wide at maturity. .
The red-tipped new growth and apple-green mature leaves make ‘Magic Carpet’ something of a specialty planting. It’s best used as a focal point. For a more conservative shrub that will settle in nicely with other border plants, or as an attractive massed bed, ‘Little Princess’ is my first choice.
The leaves of ‘Little Princess’ are a darker medium green, and the shrub has a pleasant rounded shape. (If planted in partial shade, the growth pattern will be more open.) In the fall the leaves turn a soft red.
Instead of the washed-out, barely pink flowers of most common spireas, ‘Little Princess” flowers form deep pink clusters that gradually fade to pale pink. In full bloom, it is common for both colors to be present at the same time. Re-bloom can be encouraged by trimming back the shrub lightly after its first growth (in Zone 5, first bloom is mid-June to early July).
Spireas prefer full sun but can manage light shade. They are known for being easy to grow in some of the worst soils, and, as long as they are regularly watered in their first year, they survive well with only average rainfall. ‘Little Princess’ is hardy in Zones 4-8.
Spireas have few insect or disease problems when planted in full sun with adequate air flow. Aphids could be a problem; powdery mildew is possible on overgrown plants in humid environments; leaf spot can occur in cool, moist climates; and, as a member of the Rosaceae family, spirea is susceptible to fireblight, although the occurrence is rare.
The main issue with any compact spirea is that growth can become scraggly–smaller branches don’t leaf out, while other branches shoot up higher than normal. To keep spireas looking attractive, the plant can be cut back at any time during the active growing season. For major rejuvenation, cut back the entire plant every three years to approximately 6″ (15 cm) above the ground before plants begin to grow in the spring.