Native to the temperate climate areas of southern Asia, from India to China, the rose of Sharon (Hibiscus syriacus) grows up to 10 feet tall and 6 feet wide. A woody shrub, it only goes dormant in winter and drops its leaves, resprouting them in spring after the threat of frosts pass. Gardeners enjoy the rose of Sharon since it displays large, trumpet-shaped flowers that look like tropical hibiscus blossoms from midsummer to fall.
Rose of Sharon shrubs persist only in regions with compatible winter temperatures. Extreme temperatures in winter -- both too warm and too cold -- kill the shrubs. Grow rose of Sharon in U.S. Department of Agriculture plant hardiness zones 5 through 9b. The winter temperatures in these areas drop into the minus 20 to plus 30 degrees Fahrenheit range annually.
Causes of Death in Winter
Any shrub, including a rose of Sharon, that is stressed by drought or other environmental factor is more likely to sustain damage from cold during the winter. Rotting roots from wet soil, a disease or insect pest infestation that lingers from summer and weakens the shrub may cause an unhealthy plant to die during winter. If winter weather is unusually cold or dry, or if the rose of Sharon is bombarded by drying winter winds, some branches may die back, even as far as the ground. New growth will sprout in spring only if roots remain alive.
Various rose of Sharon shrub twigs or branches may partially die back over winter, regardless of USDA zone. Withhold pruning dead plant tissues until early to mid spring when the threat of frost no longer occurs. According to the University of Connecticut, harsh pruning of these plants, to a height 6 to 18 inches tall, results in vigorous regrowth and larger flowers later in summer. Rose of Sharon regrowth is rather slow to appear in spring, as it needs warm air and warm soil temperatures to start growing.
To determine whether your rose of Sharon or any parts of branches are dead after the winter, check the branches. Dead branches are brittle and shriveled, and shatter when bent. Live twigs or branches bend slightly when given some pressure. Living branches have a light green, moist layer under the bark. Since growth is slow to appear in spring, wait to prune back rose of Sharon until you see swelling buds and leaves emerging. Leaves only grow from living tissue.
- University of Connecticut: Hibiscus Syriacus
- "A-Z Encyclopedia of Garden Plants"; Christopher Brickell and H. Marc Cathey, eds.; 2004
- Photo Credit Jupiterimages/Photos.com/Getty Images
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