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Hibiscus syriacus ‘Diana’ (photo courtesy of Linda Lamb Peters)
Hibiscus syriacus ‘Diana’ (photo courtesy of Linda Lamb Peters)

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Zone
Zones 2-24, 28-41, H1
Full Sun
Full
Regular Water
Moderate

Hibiscus syriacus

Rose of Sharon, Shrub Althaea
Malvaceae
Deciduous, Shrubs

HIBISCUS

Big, brilliant flowers on plump shrubs rank this among the showiest flowering shrubs in Western gardens. Some are very tender tropical species grown in Hawaii, others very hardy. Plants typically bear funnel-shaped blossoms, often with prominent stamens.

Giant whitefly is the most important pest of hibiscus in central and Southern California, coating the undersides of leaves with wax and eventually defoliating the plant. A parasitoid wasp has been released to control it, and research continues on its control.

Hibiscus syriacus (photo courtesy of Proven Winners)
Hibiscus syriacus (photo courtesy of Proven Winners)

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Hibiscus syriacus

Deciduous shrub from eastern Asia. Grows to 10–12 ft. tall and 6 ft. wide. Upright and compact when young, spreading and open with age. Easily trained to a single trunk with a treelike top or as an espalier. Sometimes kept trimmed as a hedge. Leaves are to 4 in. long, often three lobed, coarsely toothed. Leafs out later in spring than most other deciduous shrubs; foliage drops in fall without coloring.

Blooms from mid- or late summer until frost, resembling a bush covered with hollyhocks. Blossoms are single, semidouble, or double, 1 1/2–3 in. across; some have a conspicuously contrasting red to purple throat. Single flowers are slightly more effective, opening somewhat wider, but they tend to produce many unattractive capsule-type fruits—which in turn produce many unwanted seedlings.

Easy to grow. Prefers heat, tolerates some drought. Prune to shape; for bigger flowers, cut back the previous season’s growth in winter, cutting down to two buds. Where winter temperatures drop to –10°F/–23°C or lower, protect young plants with a winter mulch for the first few years.

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