Revised by Joey Williamson, HGIC Horticulture Extension Agent, Clemson University, 09/15. Prepared by Marjan Kluepfel, HGIC Information Specialist, and Bob Polomski, Extension Consumer Horticulturist, Clemson University. New 05/99. Images added 05/09.
Spireas (Spiraea species) are among the easiest flowering shrubs to grow. These attractive shrubs are fast growing and should be grown in full sun for best flowering. They can, however, tolerate partial shade. Some are spring bloomers; whereas others bloom in the summer. Plant sizes vary by species and cultivar, and they range from 1½ to 8 feet tall. There are many species of spireas (greater than 80), but only the most commonly encountered species and cultivars are included here.
Baby's breath spirea (S. thunbergii), also called thunberg spirea, is a showy, graceful shrub from 3 to 5 feet high and wide, with many slender, arching branches. The small, narrow, toothed leaves turn orange in late fall. The tiny white flowers are clustered in the axils along the stems in spring. More than any other spirea, it has a feathery appearance. These are some of the earliest bloomers. Prune soon after flowering if needed. For USDA zones 4 to 8.
Vanhoutte spirea (S. x vanhouttei) in full bloom.
Joey Williamson, ©2008 HGIC, Clemson Extension
Vanhoutte spirea (S. x vanhouttei) is a deciduous broadleaf shrub with an arching branch habit that can grow 5 to 8 feet high and spread as much as 7 to 10 feet wide. The Vanhoutte hybrids are crosses of S. trilobata and S. cantoniensis. The small leaves are blue-green in summer with no appreciable fall color. Masses of small, white flower clusters cover the plant in the spring. For USDA zones 3 to 8.
Flower clusters of Vanhoutte spirea (S. x vanhouttei).
Karen Russ, ©2008 HGIC, Clemson Extension
Reeves spirea (S. cantoniensis) is a white, single-flowered shrub with a white bridal wreath growth habit. The straight species is rarely encountered, whereas double-flowered cultivars are more common in South Carolina landscapes. The shrub grows 5 to 6 feet tall. In the Upper South the small green leaves may turn red in fall. In the Deep South they remain on the plant without changing color. Prune after flowering if needed. For USDA zones 5 to 8.
Bridal wreath spirea (S. prunifolia) is an early blooming, deciduous shrub with white, double flowers that appear before the foliage in the spring. This spirea grows to about 6 feet tall and wide. Prune, if necessary, soon after flowering. Fall color is red to orange. These are often found at old home sites and are hardy from USDA zones 5 to 8. Other species of spirea, such as the Vanhoutte spirea, are often sold as “bridal wreath spireas” in catalogs.
Although spireas are typically not large plants, they do grow quickly.
Spireas are valued for their form and flowers. They are used as a specimen plant or as a hedge, screen, or border. Smaller cultivars can make nice accent plants for a border perennial garden. Most spireas are deciduous shrubs, and some have colorful fall foliage. Spirea flowers are often visited by butterflies. Spireas are generally deer resistant.
Fall is the best planting time, as it is for most shrubs. Spireas are also easy to dig and transplant to new sites, and late fall after leaf drop is the best time for moving these shrubs. These shrubs grow best, more dense, and produce more blooms in full sun. Spireas are tolerant of many soils except those that are extremely wet. The plant also responds well to applied mulch and summer watering.
After flowering has finished, prune the mostly spring-blooming spireas. Thin out old and weak canes to the ground annually. Prune the summer-blooming, bumalda spireas in winter or early spring. The bumaldas generally need less severe pruning than other species of spireas. After flowers on any spirea cultivar fade, remove them and a second flush of growth is stimulated, which will result in additional flowers.
Like other members of the rose family, spireas are susceptible to various pests and diseases, but most are not serious.
Diseases: Phytophthora or Pythium root rots could occur in poorly drained, wet soils, but these soils should be avoided for almost any type of shrub.
Phyllosticta and Cylindrocladium leaf spots have been reported on S. x bumalda cultivars, but are uncommon. Any shrub watered by over-head irrigation is more apt to contract a foliar fungal disease, so drip irrigation is always the best choice. Sprays with chlorothalonil (such as Daconil) will help control fungal leaf spot diseases. Rake or blow out fallen diseased leaves during the late winter and dispose of them to aid in disease control.
Insect Pests: Aphids are occasionally a problem in the spring. Spray in the early evening with an insecticidal soap solution for aphid control, and repeat sprays as needed.
Invasiveness: Japanese spirea (Spiraea japonica) is considered invasive in the Southeast US. Because of this potential, Japanese spirea and its cultivars are not recommended as suggested landscape plants*. Bumalda spireas (S. x bumalda) are crosses between S. japonica var. albiflora and S. japonica. These are also Japanese spireas and may be invasive. The most commonly produced cultivars, and there are many, are included last for purely educational purposes, so that if cultivar names only are listed in a catalog or in a nursery, SC residents will realize that these are Japanese spireas.
Reference: *The Southeast Exotic Pest Plant Council
Cultivars for SC Landscapes
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This information is supplied with the understanding that no discrimination is intended and no endorsement of brand names or registered trademarks by the Clemson University Cooperative Extension Service is implied, nor is any discrimination intended by the exclusion of products or manufacturers not named. All recommendations are for South Carolina conditions and may not apply to other areas. Use pesticides only according to the directions on the label. All recommendations for pesticide use are for South Carolina only and were legal at the time of publication, but the status of registration and use patterns are subject to change by action of state and federal regulatory agencies. Follow all directions, precautions and restrictions that are listed.