Tropical hibiscus

About Tropical hibiscus

Tropical hibiscus, also called Chinese hibiscus, is an evergreen shrub with glossy leaves and huge flowers 3-6 inches or more across in red, pink, orange, yellow, white and blends (NC State). Each flower lasts only about a day, but plants in sun bloom almost nonstop from spring to fall (LSU AgCenter; UF/IFAS), and hummingbirds and butterflies visit them. It isn't the cold-hardy hibiscus or rose of Sharon, which have their own entries; outside the Deep South it's a patio and container plant that spends winter indoors.

Grows outdoors all year in zones 9-11 (NC State); in north Florida it freezes to the ground but often regrows from the roots (UF/IFAS). Protect it from temperatures below 45 F (LSU AgCenter); elsewhere grow it in a pot and overwinter it indoors.

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.

Set plants out after frost danger has passed, where they get 6-8 hours of direct sun (LSU AgCenter). Many bloom best a little root-bound, so don't over-pot, and expect some bud and leaf drop after a move (LSU AgCenter, NC State). For winter, bring it in before nights fall regularly below the mid-50s to 45 F: give it a sunny south or west window, water less and skip fertilizer until new growth starts, or let it go dormant in a cool spot with the roots barely moist (UMD, MU Extension, Smithsonian Gardens). Days to first bloom aren't documented; nursery plants are usually sold in bloom.

Soil

Rich, well-drained soil high in organic matter that stays evenly moist; work sand and organic matter such as pine bark into heavy clay (NC State, LSU AgCenter).

Test the soil and aim for pH 6.5-6.8; work sand and organic matter such as pine bark into heavy clay so it drains (LSU AgCenter).

Feeding

• Spring through fall, while it's growing and blooming: fertilizer with two to three times as much potassium as nitrogen, such as 12-4-18, or slow-release granules plus a water-soluble bloom fertilizer. Feed regularly through the season (Smithsonian Gardens); LSU AgCenter suggests pairing slow-release granules with water-soluble feed when you water. Follow label rates.
• Late winter or spring, when an overwintered plant starts new growth: water-soluble fertilizer. Skip or cut back feeding over winter, then resume once new growth shows (Smithsonian Gardens, UMD).

Don't let it dry out: that's the main cause of bud drop and yellow leaves (LSU AgCenter). Never spray malathion on hibiscus (UF/IFAS).

Harvest

Flowers open on new growth from spring through fall, nearly all year in South Florida, and each lasts about a day (UF/IFAS, NC State). Cut plants back by about half in early spring for a compact shape; pruning delays flowers for a while but doesn't stop them (NC State, Smithsonian Gardens).

Varieties (3)

Sources we could open document only these 3 (two series and one patented cultivar); hundreds of named hybrids exist.

Pests to watch for

Aphids, Whiteflies, Mealybugs, Thrips, Twospotted spider mite, Scale insects

Diseases and problems

Sooty mold

In the kitchen

NC State lists the flowers as edible; use only blooms from plants that haven't been sprayed.

Safety: Neither NC State nor the ASPCA lists toxic parts. If you eat the flowers, pick them from plants you haven't treated with pesticides.

Pets: Not listed separately by the ASPCA; its hibiscus entry (H. syriacus, which also gives the name rose of China) is non-toxic to dogs, cats and horses.