The four species of deciduous shrubs that make up the genus Exochorda of the Rosaceae, or rose, family are native to woodlands in parts of Korea, China, and central Asia. Often gardeners refer to the shrubs as pearl bush because the buds resemble white pearls. Growers raise the shrubs primarily for the abundant cup- or saucer-shaped white flowers that bloom in spring or summer. Bushes are typically a mass of white flowers when the shrub is in full bloom.
The leaves of Exochorda shrubs are not remarkable, but may provide garden color when they turn yellow in autumn. They are simple, oblong, or obovate in shape and may or may not be toothed at the edges, depending on the species and cultivar or hybrid. Usually the leaves are 2 to 3 inches (about 5 to 8 cm) long and various shades of green. In some species, the leaves and shoots are pinkish when young. E. racemosa, or common pearl bush from northern China, has two-toned leaves that are light green on top and darker green underneath.
Typically, the Exochorda flowers grow on upright racemes bearing six to ten pure white blooms. The flowers are usually between 1 to 2 inches (2.5 to 5 cm) in diameter. When planted as a hedge or border, the flowering shrubs often are a dramatic garden focal point.
One of the most popular garden specimens is the bride, a cultivar of the species E. korolkowii and E. macrantha. As a compact shrub, it typically measures 6 feet tall by 10 feet wide (about 2 by 3 m). Another popular choice is the species E. giraldii, or red bud pearl bush, which has pale green leaves with red veins. E. korolkowii has 3.5-inch (about 9-cm) long leaves that typically are olive to lime green.
In their native lands, Exochorda plants grow in temperate regions. In the U.S., they usually grow in USDA hardiness zones five to nine, depending on the microclimate, species or cultivar, and other factors. Generally, growers propagate the shrubs by sowing seeds or by rooting softwood cuttings. Most of these shrubs thrive in fertile, moist soil that has enough drainage to keep the roots from being soggy. They prefer sunny areas or a lightly shaded spot.
Most gardeners plant them in the role of solitary specimen plants, especially at the edges of woodlands. Gardeners may also use Exochorda plants as shrubby borders, which they may trim as informal hedges. All four of the species and their cultivars may benefit from a systematic pruning of the branches that have spent blooms. The shrubs flower on the previous year's growth. Therefore gardeners usually do not prune the current year's new growth. Cutting back old growth often helps promote new vigorous growth.