Althea, more commonly known as the Rose of Sharon (Hibiscus syriacus), is a multi-stemmed shrub that typically grows upright with a vase-shaped or rounded habit. It features attractive green foliage that may turn yellow in fall before dropping. The most notable feature of Althea is its large, showy flowers, which resemble hibiscus blooms. These flowers come in a variety of colors, including white, pink, purple, and blue often with a contrasting throat. They bloom profusely from mid- to late summer and continue into fall, attracting bees, butterflies, and hummingbirds.
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Scientific Name
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Hibiscus syriacus
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Foliage: Deciduous
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It loses its leaves in the winter. The leaves are medium green, often three-lobed, and have a "toothed" edge. They are usually one of the last plants to leaf out in the spring (don't worry if it looks dead in April!)
Flowers: Large, trumpet-shaped flowers (2–4 inches wide) come in shades of white, pink, red, purple, or blue, often with a contrasting "eye" in the center.
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Mature Height
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8-12 feet |
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Mature Width (Spread)
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6-10 feet |
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Growth Rate
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Moderate (typically 1-2 feet per year) |
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USDA Zone
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5-9 |
Plant Care & Characteristics
Light Requirements: Full Sun to Partial Shade. It blooms most prolifically in full sun (6+ hours). In hotter climates (Zone 9), it appreciates a little afternoon shade to keep the flowers from wilting.
Water Requirements: Moderate. It prefers consistently moist, well-drained soil. While it is somewhat tolerant of wet soil, it does not like to sit in a swamp.
Drought Resistance: Moderate. Once established, it can handle short dry spells, but its flowering will be significantly reduced, and it may drop flower buds if it becomes too thirsty. Althea benefits from regular watering during dry periods, especially in hot weather.
Soil Type: Adaptable. It thrives in rich, loamy soil but is quite tolerant of various types, including clay and sandy soils, as long as they drain well. It prefers a slightly acidic to neutral pH. Adding organic matter, such as compost, to the soil can improve its fertility and drainage.
Deer Resistance: Moderate. Deer may eat the flower buds or young leaves, so it may need protection if you have a high deer population.
Maintenance: Common varieties of Rose of Sharon are notorious for producing a massive amount of seeds that sprout everywhere in the garden. If you want to avoid weeding out hundreds of "babies," look for sterile cultivars such as the 'Chiffon' series or the 'Satin' series (e.g., 'Blue Satin'), which produce few to no seeds. Althea benefits from occasional pruning to control its size and shape and to promote flowering by removing dead or damaged branches. Pruning is best done in late winter or early spring before new growth begins. Applying a balanced fertilizer in spring can help encourage healthy growth and flowering.
