This article appeared in the July 2002 web issue of Horticulture Update,
edited by Dr. William C. Welch, and produced by Extension Horticulture,
Texas Cooperative Extension, The Texas A&M University System, College Station, Texas.

Althaea, Rose of Sharon,
Hibiscus Syriacus

By Dr. William C. Welch, Landscape Horticulturist
Texas A&M University, College Station

ost Southerners have childhood memories of althaeas. They were once one of the most popular ornamental shrubs in our region.

My memory is of a huge double-pink specimen planted at the side of my grandmother’s home in south central Texas. It must have been fifteen feet tall and almost as wide. From May through most of the summer it was laden with double, fluffy pink flowers. Anyone who seriously wanted a plant could root 10- to 12-inch stems during the winter by putting them into any good garden soil, and watering them every few days if rain was lacking. The cuttings were usually ready to transplant the next fall.

Althaeas grow quickly and need little attention. They thrive in the heat of summer and require only occasional deep watering to keep them growing and blooming.

Native to China and India, they have been cultivated as long as records exist. The Chinese used the flowers and leaves for food. Thomas Jefferson grew them from seed, and was documented to have planted them at all three of his homes.

Colors range from white to pink, lavender, and reddish purple. Several kinds have dark-colored centers in the flowers, and single-flowering types are quite common. Seedlings often sprout in nearby areas. Propagation from cuttings is usually preferred, because unlike seedlings, rooted cuttings will be exactly like their parents. Althaeas are cold hardy over most of the nation.

About the only serious problem is cotton root rot, which can kill plants of any age, and for which there is no practical control. Cotton root rot is mainly a problem in alkaline soils. Bud drop may occur when plants are under stress from too much or too little water.

Newly planted althaeas should be watered every few days, like most other plants. Specimens located in sunny areas bloom much better than those planted in the shade.

The National Arboretum released several new althaeas in the 60s and 70s. These are all sterile triploids that have larger, earlier flowers, but they set no seed. Cultivars include ‘Diana’ (white), ‘Helene’ (white with maroon throat), ‘Minerva’ (lavender), and ‘Aphrodite’ (pink). Another cultivar released a number of years ago is ‘Bluebird’, which is a single-flowering lavender-blue color. All these newer introductions tend to be more compact in form than the species types, and I find them better adapted to the northern half of Texas than the south.

Wherever you live, althaeas are a good possibility for use as large, deciduous hedges or specimens. Heavy pruning promotes vigorous growth and flowering, but creates unsightly stubs. By removing lower limbs flush with the main trunks, althaeas may be used as small trees, much like crape myrtles.

Almost every southern nursery that sold ornamental plants in the 19th century listed althaeas. They probably deserve wider use in today’s gardens, as we seek drought-tolerant, easily grown plants that provide color over a long season. Few non-native plants are as well adapted to our area.