Spirea is a group of woody smaller leafed shrubs that, depending upon type, bloom on long, arching or on more compact stems in either spring or summer, or in flushes throughout the season. They are typically classified as spring or summer blooming. Early-spring blooming spirea most often has a delicate cascading habit with large clusters of white flowers on arching branches while later in the spring, look for a broader range of colors on a more diverse size shrub. Summer blooming spirea are usually a more upright shape with beautiful pink, white or red flowers.
Spirea's foliage is also a standout—depending on the variety it can be green or blue-green but also can morph into different shades from spring to fall. All spirea are deciduous, losing their foliage in fall.
The spirea you are probably most familiar with is a bridal wreath, a larger type that stuns in spring with an unforgettable display of cascading branches smothered in white flowers. More compact types, such as the japonicas, are indispensible team players in foundations, middle-to-front of borders, and even in containers. Pairing well with lots of other shrubs (see below), they provide simple, elegant green filler when not in bloom, amplifying the impact of summer bloomers such as roses and hydrangeas.
While there are quite a few species of spirea (80+!), here the ones you are most likely to find readily available at garden centers:
Japanese spirea (Spiraea japonica) Offering the greatest range of sizes (dwarf right up to 5' or taller) and flower and leaf colors, Japanese spirea produces lavish clusters of white, light pink, rosy-red or purple flowers in late spring and summer. Finely textured green or blue-green foliage is most typical, but this is where to look for cultivars with luminous yellow or chartreuse foliage that changes color throughout the season.
Bridal wreath spirea (Spiraea prunifolia) Gardeners have planted this old-fashioned classic for generations (if you have an older bridal wreath in your garden, lucky you!) seduced by the brilliant display of double white flowers that cover bare branches in early spring. Give this one room to do its thing--it reaches 4 to 8 feet high and 6 to 8 feet wide and those arching branches benefit from negative space.
Nippon spirea (Spiraea nipponica) Nippon spirea, commonly known as snowmound spirea, is a relatively smaller, upright, mounded shrub reaching 4 to 5 feet tall and wide. Look for a late spring frothy shower of clustered, small, white flowers that cover the limbs like a mound of snow followed by signature deep blue-green leaves during the summer months.