Several varieties of the late-summer scene-stealer hibiscus are hardy even where climates are less than tropical, including rose mallow (Hibiscus moscheutos; USDA zones 5 through 10), rose of Sharon (Hibiscus syriacus; USDA zones 5 through 9), Texas star hibiscus (Hibiscus coccineus; USDA zones 6 through 9) and confederate rose (Hibiscus mutabilis; USDA zones 7 through 9).
All of these plants produce many showy flowers that last one day each on canes that grow up from the roots each spring. The plants are also easily propagated by seed – indoors or out – and can bloom in their first season.
Indoors From Purchased Seed
Nick the Seed Coat
Soak the Seeds
Soak the seeds in a small bowl of hot water for up to 24 hours. Begin the sowing process 12 weeks before your last expected spring frost.
Prep the Planting Tray
Fill a planting tray with moist seed-starting mix, usually a soil-less product that combines perlite, vermiculite and peat moss.
Sow the Seeds
Sow the seeds 1/4 inch deep, firming the moist seed-starting mix over the seed. Place one seed per plug if your seed tray has inserts that hold the mix in separate 1- to 2-inch compartments. Otherwise sow seeds a few inches apart so seedlings will be easy to remove later.
Keep Them Warm
Set the tray on a waterproof greenhouse heat mat set to 68 to 72 degrees Fahrenheit or in a room with the same temperature range.
Cover the tray with its included clear plastic dome or with plastic wrap to keep moisture in.
Check the Seed Tray
Check the seed tray regularly over the one to three weeks it takes the seeds to germinate. Ensure the soil is moist but not soggy. Too-wet soil can cause the seeds to rot before they germinate.
Remove the Plastic
Remove the plastic when plants emerge and move the tray to a site where it receives bright, indirect sunlight.
Apply a balanced, water-soluble fertilizer mixed to half its recommended strength with every other watering after the seedlings produce their first true leaves – the first pair of leaves after the initial seed leaves that emerge at germination. Water enough to keep the potting soil evenly moist, never letting it dry out or become waterlogged.
Transplant the Seedlings
Transplant the seedlings to separate 1-gallon containers filled with standard potting soil when they have at least three sets of leaves. Allow them to grow in a sheltered area for several weeks before transitioning them to their permanent outdoor location when all danger of frost has passed.