Thursday, October 26, 2017
By Libby Heldman
OSU Ext. master gardener volunteer
Known for its late-summer profusion of blooms, rose of Sharon adds beauty to any landscape after many plants have already completed their bloom period for the year. One can stand alone as a specimen plant, or several can form a privacy hedge or screen.
Rose of Sharon, Hibiscus syriacus, can be grown as a small tree or as a large shrub. I have four along my property line. One can grow 12 feet tall and 10 feet wide in an upright shape. The green leaves have three lobes, 2 to 4 inches long, and are placed alternately along the stem.
The flowers are tropical in appearance and have five petals. Some varieties have flowers that are single, and some are double. Although most often the flowers are pink, selections are available with red, purple, white and even blue flowers. Rose of Sharon blooms from July through September, often during the hottest and driest time of the year.
It is fairly easy to grow, needing minimal care. It prefers to grow in full sun to partial shade, in moist, well-drained soil. It will tolerate winds and salt conditions in soil, but if drought conditions occur, it needs to be watered.
Pruning is usually not required since the plant grows slowly and keeps a tight, upright form. If several are growing close together, you may wish to prune to increase sunlight and air. Shaping and pruning can be done at any time. In our Zone 5, it is best to prune in late winter or early spring (late February or early March). Little or no pruning gives many smaller flowers; frequent or severe pruning gives larger but fewer flowers.
Rose of Sharon is usually strong and easy to grow, but it can be bothered by aphids. These can be dislodged with high-pressure water sprays from the garden hose.
As with any growing plant, unusual weather and changes in the environment can make the rose of Sharon susceptible to disease. If leaf spots, particularly bacterial leaf spots, are seen, pick off and destroy infected leaves. Canker can be a problem and can kill a branch or the entire plant if grown in a wet spot. Bright, reddish-orange fruiting bodies may appear on the bark. Remove any infected branch. Be alert for powdery mildew and wood rot.
Rose of Sharon is a great, hardy choice that grows large and blooms beautifully. One problem can be reseeding of the plants throughout the garden. Although most of us grew up calling it the rose of Sharon, it is known to others as shrub Althea.
To learn more about this plant, go to: http://go.osu.edu/roseofsharon.