Rose of Sharon (Althea)

Hibiscus syriacus

Althea grows 8 to 12 feet high and 6 to 10 feet wide. It grows as a shrub or small tree with very erect branches. It has a vase shaped, multi-stemmed growing habit. It is deciduous.

It transplants well and grows in about any soil except those extremely wet or dry. Does best in moist, well-drained soils supplemented with organic matter. Althea grows in a wide range of pH levels. It flowers best in full sun but will do ok in partial shape. Prefers hot weather so does well in southern gardens. Very tolerant of summer heat and humidity. Generally tolerant of urban conditions. Prune to shape in spring. Prune althea heavily in early spring. This will encourage larger flowers. The leaves of althea are medium to dark green in the summer. They hold their color late and have a poor yellow fall color. Sometimes althea tends to leaf out late in the spring so do not worry if this happens to you.

Althea flowers in July, August through September. Flowers can be white, red, purple, violet or a combination. Flowers can be single or double. Flowers are typically 2-4 inches across. Many cultivars are available. Our favorite is Blushing Bride which has double pink flowers.

Hibiscus plants are like daylilies in each flower only lasts one day. If flowers are not deadheaded a 5-valved fruit capsule will persist through the winter. Seeds require no pre-treatment for propagation and therefore can self-sow which may be a nuisance in the landscape. We have not seen any self-sowing althea in our garden.

This shrub is native to China, India, Japan and Korea. It is the national flower of South Korea. It is also commonly called shrub althea. Hibiscus means mallow. At the time this species was named, it was mistakenly believed to be native to Syria, hence the now misleading specific epithet.

No serious insect or disease problems. Some susceptibility to leaf spots, blights, rusts and canker. Japanese beetles, whiteflies and aphids are occasional insect visitors. Japanese beetles can severely damage foliage if left unchecked.

Excellent flowering shrub that may be massed, planted in groups or used as a specimen. Good for foundations and shrub borders. Also can be effective as a hedge or screen.