Hibiscus syriacus is an ornamental shrub that is native to China and India. At maturity, it stands at about 8 feet (2.4 m) in height and 4 feet (1.2 m) in diameter and features large, colorful five-petal flowers. Other names for the shrub are Rose Althaea, Shrub Althaea and Rose of Sharon.
This plant is widely planted in climates that have hot summers. It does well in full sun to partial shade and offers continuous blooming from mid-summer through early autumn. Its flowers are about 2-4 inches (5.1-10.2 cm) in diameter and are produced on the current season's growth. Coloration for the showy blossoms range from solids of white to magenta to blue. Bicolor blossoms with the throat a different color than the petals are commonly cultivated.
The trunk of hibiscus syriacus is grayish and generally smooth. Branching begins near the ground with numerous vertical branches. The lower limbs are sometimes removed to present the shrub in tree form. The natural growth pattern for the shrub is upright with spreading branches that develop into a vase-shaped profile. If not pruned, the limbs tend to arch away from center as the plant ages.
The leaves of the shrub are medium to dark green, three-lobed and about 2-4 inches (5.1-10.2 cm) in length. The surface is smooth, and the edges are slightly scalloped or toothed. The plant leafs out late in the spring, and the leaves hold late into autumn before turning a yellowish green.
Hibiscus syriacus prefers hot weather with full exposure to sunlight, though it can tolerate partial shade. The plant does best in moist, well-drained soil but it is very adaptable and can thrive in an urban environment. The shrub is easily transplanted. Propagation is chiefly by rooted stem cuttings, though it can be successfully cultivated from seed as well.
In landscaping, hibiscus syriacus is often used as a screen or shrub border. It can be planted to accent an entrance or as an informal hedge. Grouped with other plants, the shrub serves well as part of a living wall or privacy screen. Though prized for its profuse blooming throughout the summer, the shrub is less ornamentally attractive in late autumn.
Hibiscus syriacus is readily available in several popular varieties. The Bluebird variety features a blue single flower sporting a dark pink eye and reddish base. The Ardens is a purple double-flowering variety. The Red Heart produces single white scarlet-eyed blossoms. Dozens of other varieties or cultivars have been developed, some of which are not seed-bearing.