Rose of Sharon (shrub althea)

Hibiscus syriacus · Mallow family (Malvaceae)

At a glance
Hardiness zones	5 to 9
Sun	full sun to part shade
Water	moderate
Life cycle	perennial
Frost	Hardy: takes frost
Spacing	72 to 144 inches

About Rose of Sharon (shrub althea)

Rose of Sharon is a tough, upright Asian shrub that blooms in the hottest part of summer with hibiscus flowers in white, pink, red, lavender and blue. Hummingbirds, butterflies and bees visit, and the flowers are edible. It is listed as invasive in Kentucky and Georgia and in parts of Virginia, because seedy types scatter seedlings that are hard to pull; plant low-seed or sterile cultivars.

Hardy in zones 5-9. Listed as invasive by the Kentucky and Georgia Exotic Pest Plant Councils and by Arlington County and the City of Alexandria, Virginia; seedy cultivars self-sow heavily.

When to plant

Timing is counted from your average last spring frost (and first fall frost). Sow & Tell works out the actual dates for your ZIP code.

Choose a low-seed or sterile cultivar (see varieties): Clemson names 'Diana', 'Helene', 'Aphrodite' and 'Minerva' as low-seed, though an Oregon State study found 'Aphrodite', 'Diana' and 'Minerva' still set some viable seed; the double Smoothie types are sold as fully sterile. For a hedge, space plants 6-12 ft apart (NC State).

Soil

Moist, well-drained sand, loam or clay; it handles a wide pH range, some salt, and short spells of wet or dry soil.

Loosen the soil and work in compost; follow a soil test before adding fertilizer.

Feeding

Established plants: spring as growth begins (a split feeding can follow in early summer): Slow-release shrub fertilizer, about 3-1-1 or 3-1-2 ratio (3-0-1 if the soil test shows enough phosphorus). Follow a soil test. Spread it evenly over the root zone and water it in; for slow-release types Clemson's upper limit is 2-4 lb of nitrogen per 1,000 sq ft per year.

Don't fertilize a drought-stressed shrub, and don't overfeed; Rose of Sharon is tough and needs little.

Harvest

Blooms July into September on this year's growth; each flower lasts one day. Prune in late winter or early spring, removing about a third of the oldest wood; spring pruning gives bigger flowers.

Varieties (22)

Variety	Type	Notes
Blushing Bride	Double	Pink double flowers that fade to white.
Freedom	Double	Large double pink flowers all summer.
Smoothie Fusion	Double	Double flowers in purple, dark pink and light pink.
Strawberry Smoothie	Double	Large double pink flowers from midsummer to frost.
Blueberry Smoothie	Double, sterile	Double blue-toned flowers.
Peppermint Smoothie	Double, sterile	Ruffled double red-pink flowers; glossy green leaves.
Collie Mullens	Semi-double	Pink flowers with burgundy centers.
Purple Pillar	Semi-double	Lavender semi-double flowers with dark red centers.
White Chiffon	Semi-double	White flowers on graceful stems; rounded habit.
Lavender Chiffon	Semi-double, low-seed	Large lavender flowers on graceful stems; 8-12 ft.
Whit XXI	Semi-double, sterile	Soft pink flowers with extra petaloids; semi-dwarf, about 6-8 ft tall; the patent reports no seed.
Blue Bird	Single	Blue vase-shaped flowers.
Jodi	Single	Pure white flowers; leaves variegated dark green, light green and gold. A sport of 'Diana'; the patent reports no self-seeding.
Notwoodthree	Single	Large single blue flowers with a lacy center.
Pink Giant	Single	Large pink flowers with a burgundy spot at the center.
Red Heart	Single	White flowers with a deep red center.
Aphrodite	Single, low-seed	Deep rose-pink flowers.
Diana	Single, low-seed	Large pure white flowers that stay open at night; dark green leaves.
Helene	Single, low-seed	White flowers with a reddish-purple eye.
Minerva	Single, low-seed	Heavy bloomer; lavender flowers washed with pink and a red eye.
ILVO347	Single, sterile	Orchid-pink flowers with dark red centers; the patent reports no seed or fruit.
Purpureus Variegatus		Half-closed maroon flowers late in the season; green-and-yellow variegated leaves.

Pests to watch for

Aphids, Twospotted spider mite, Japanese beetle, Whiteflies, Sawflies (garden sawflies)

Diseases and problems

Leaf spot, Blight

In the kitchen

The flowers are edible (NC State).

Safety: NC State and the ASPCA list no toxic parts. Eat only flowers grown without pesticides.

Pets: Non-toxic to dogs, cats and horses (ASPCA)

Sources

Photo: Photo: Gmihail, CC BY-SA 3.0 rs, via Wikimedia Commons (CC BY-SA 3.0 rs). Photo resized for the web.

Planting dates and advice are general guidance; check with your local Cooperative Extension office for your area.