Rose of Sharon is known by the Latin name Hibiscus syriacus. It is part of the mallow (Malvaceae) family, which also includes hollyhocks, cotton and okra. The word "hibiscus" comes from the ancient Greek "hibiskos," which was used to describe mallow plants. "Syriacus" is Latin for Syria, originally thought to be the shrub's native area. It is actually native to parts of India and China. The plants are generally hardy in U.S. Department of Agriculture plant hardiness zones 3 through 8.
Latin plant names define family relationships that are identified by common characteristics. Hibiscus family members, including rose of Sharon and tropical hibiscus (Hibiscus rosa-sinensis), hardy in USDA zones 9 through 11, often roughly triangular, feature lobed leaves. Definitive plant identification usually hinges on the the flowers, which feature five petals apiece, except in double-flowered hybrids and varieties. Hibiscus petals are joined to the central stamen tube, which projects outward from the flower. This long stamen tube is the most recognizable hibiscus flower feature. Hibiscus plants generally produce an oval-shaped seed capsule with five cells.
The United States National Arboretum sponsored a rose of Sharon breeding program that produced several good varieties, named after ancient Greek deities. These include "Diana" (Hibiscus syriacus "Diana"), with large white flowers; "Minerva," (Hibiscus syriacus "Minerva"), an erect cultivar featuring lavender flowers with dark red central "eyes"; and "Helene" (Hibiscus syriacus "Helene"), with white flowers and red-purple bases. Older varieties include the double-flowered "Lady Stanley" (Hibiscus syriacus "Lady Stanley"), with pink blooms and "Blue Bird" (Hibiscus syriacus "Blue Bird"), bearing single blue-tinted flowers with red centers.
Roses of Sharon can be grown as multi-stemmed shrubs or pruned into small trees, a particularly good use for small gardens. Plants "standardized" or grown as trees can be underplanted with a variety of annuals and perennials to maximize garden space. Like tropical hibiscus, the standard forms can also be grown in large containers. Rose of Sharon makes an excellent flowering hedge, but can also function as a specimen or stand-alone shrub. The plants are pollinated by insects or birds and are good choices for pollinator-friendly planting schemes.
Rose of Sharon has many advantages. It is undemanding, tolerant of different soil types and somewhat resistant to deer browsing. It can also be grown near black walnut trees without succumbing to the growth inhibiting substances produced by the trees' roots. The shrubs have a significant disadvantage-- potential invasiveness. Roses of Sharon bear seeds that germinate at a high rate, producing many unwanted offspring. If not monitored, these offspring can spread into naturalized areas. Always prune the shrubs as soon as the flowers fade and buy varieties that are listed as producing few or no fertile seeds.