How to grow Hibiscus

Where to plant

Both need full sun and well-drained soil; roselle does poorly in shade. Roselle is hardy only in zones 9 and 10 and is damaged by frost, so the harvest must finish before temperatures drop below about 40°F. It is a short-day plant that only flowers as the days shorten in fall, which is why it needs a long, warm season.

Tropical hibiscus stays evergreen in South and Central Florida. In North Florida it freezes to the ground but usually returns from the roots, and even a slight cold snap makes the lower leaves yellow and drop.

• Florida and Hawaii: grow roselle in the ground from a spring sowing, and tropical hibiscus as a garden shrub. In Florida roselle can also be planted in August.
• The Gulf South, Texas, the Desert Southwest and California: roselle can work where fall stays frost free long enough for the calyces to mature. Grow tropical hibiscus in a sheltered spot or a pot you can protect.
• Farther north, including the Northeast, Northern Plains and Mountain West: tropical hibiscus is a patio plant. Move the pot outside after the last frost and bring it back in before the first. Roselle needs a longer warm season than these regions give.
• Alaska: grow tropical hibiscus as a houseplant in a sunny window.

Choosing a variety

For roselle, UF/IFAS reports that 'Victor' has done well for gardeners in South Florida. For tropical hibiscus, choose any garden center variety by flower color and size; the flowers often last a day, but plants bloom over a long season.

How to grow roselle

1. Sow seed in March or April in trays or straight into the ground. Seedlings usually appear in 5 to 10 days. Roselle also roots easily from cuttings.
2. Pot seedlings on into 1 to 3-gallon pots in May or June, or plant them straight into the garden in spring, in full sun.
3. Give each plant plenty of room, as mature plants reach 5 to 7 feet tall and 3 to 5 feet wide.
4. Pinch or prune the young plants early so they branch, which gives more flowering shoots and more calyces.

Watering and feeding

Water roselle whenever rainfall is not enough, keeping the soil evenly moist but never waterlogged. Tropical hibiscus also flowers best with steady moisture and regular feeding through the warm months; potted plants dry out quickly in summer.

Pruning and care through the year

• Rotate roselle around the garden each year, as root-knot nematodes are its main pest in Florida.
• Save seed from your best roselle plants each fall, since it is grown as an annual.
• Prune tropical hibiscus lightly after a flush of flowers to keep it bushy. In North Florida, plants frozen to the ground usually regrow from the roots in spring.

Harvesting

Roselle flowers from about September or October in Florida. After each flower drops, the calyx swells into a fleshy, bright red cup around the seed pod. Pick the calyces while they are plump and tender, before they turn brown, usually in October and November and sometimes into the new year. Picking encourages more flowers.

Pull or cut the calyx away from the green seed pod before using it. Fresh calyces keep for about a week; dry or freeze them for longer storage. One plant can give as much as 12 pounds in good conditions.

Growing in pots

Tropical hibiscus is an excellent container plant for regions with frost. Use a large pot with drainage holes and good potting mix, keep it in full sun outdoors in summer, and move it into a bright spot indoors before the first frost. Water less in winter.

Using it

Brew roselle calyces fresh or dried for hibiscus tea, or cook them into jam, jelly, syrup, cordial and a cranberry-style sauce. They can stand in for rhubarb in crisps and pies. The young leaves are tangy and can be cooked as a green or added raw to salads.