Hibiscus sabdariffa aka Roselle

Hibiscus sabdariffa is a fast-growing plant that typically reaches 2-3 meters (6-9 feet) in height with a spread of about 2 meters (6 feet). Fiber varieties can grow up to 4.5 meters tall, while edible cultivars tend to stay around 1.5 meters. The plant develops a deep taproot system and produces woody stems at the base. Young foliage has simple single-lobed leaves that mature into distinctive 3-5 lobed leaves as the plant grows.

Hibiscus sabdariffa thrives in warm temperatures between 12.5-27.5°C (55-82°F), with optimal growth at 24-32°C (75-89°F). The plant is highly frost-sensitive and will be killed by freezing temperatures. It grows as a perennial in USDA zones 8-11 and as an annual in cooler zones 3-7. In tropical and subtropical climates, it can survive year-round, but in temperate regions it must complete its life cycle before the first frost.

Hibiscus sabdariffa produces striking cup-shaped flowers from August to November, typically 3-6 inches across. Flowers are gold, yellow, or white with a distinctive dark red center. As a short-day plant, it requires 12 or more hours of darkness to initiate flowering, which is why blooming occurs in late summer to fall. The flowers are hermaphrodite (containing both male and female organs) and are self-fertile. After flowering, the fleshy red calyces develop and are ready for harvest about 3 weeks after the flowers drop.

Hibiscus sabdariffa has two main subspecies. The subspecies sabdariffa has long branches reaching about 1.5m, produces red or pale yellow edible calyces, and has poor quality fiber - this is the type grown for food and beverages. The subspecies altissima is unbranched, grows up to 4.5m tall, produces leathery inedible calyces, and is cultivated for high-quality fiber. Popular edible cultivars include 'Victor', 'Rico', and 'Archer'. There is also a 'white sorrel' variant with greenish-white fruits instead of red.

Hibiscus sabdariffa is primarily an outdoor plant that requires full sun and performs best in garden or field settings. It grows as a perennial in USDA zones 8-11 and as a rapid-growing annual in zones 3-7. The plant needs a long growing season (90-150 days) for calyces to mature, which can be challenging in cooler climates with short summers. It prefers tropical lowland conditions at elevations up to 600 meters with annual rainfall of 1,500-2,000mm. Plant after the last frost when soil has warmed.

Pruning young Hibiscus sabdariffa plants encourages bushier growth. When stems reach about 18 inches (45cm), pinch or cut 2-3 inches from the tips just above a node. Remove dead, diseased, or crossing branches to improve air circulation and prevent fungal issues. Regular pruning is not necessary for most garden plants.

Hibiscus sabdariffa is easily propagated from seeds, which germinate very rapidly. Sow seeds about 6mm (1/4 inch) deep, spacing them 30-45cm (12-18 inches) apart. Germination can be improved by abrading or soaking seeds beforehand. Seeds can be started indoors in a warm greenhouse or sown directly outdoors after the last frost. The plant can also be propagated from half-ripe wood cuttings taken in July-August. Cut 15cm (6 inch) stems through a node, apply rooting hormone, and keep in water and sunlight until roots develop.

Hibiscus sabdariffa is generally pest and disease resistant, but can be affected by common garden pests including aphids (particularly yellow aphid Aphis gossypii), whiteflies, spider mites, mealybugs, and scale insects. Root-knot nematodes may affect roots, though the plant shows some resistance. Cotton stainers can damage ripening calyces. In humid conditions, mildew (Oidium) and root rot may occur. Control aphids and whiteflies with insecticidal soap or neem oil. Prevent root rot with well-draining soil and avoid overwatering.

Hibiscus sabdariffa flowers are hermaphrodite, containing both male and female reproductive organs, and the plant is self-fertile. Pollination is primarily carried out by insects including bees, butterflies, and hoverflies. Hummingbirds are also attracted to the flowers. While the plant can self-pollinate, insect visitors improve fruit set and seed production. The flowers open in the morning and are receptive to pollination for about one day before the petals fall.

All parts of Hibiscus sabdariffa are edible. The fleshy calyces are the most prized part, eaten raw in salads or used to make the famous hibiscus tea (known as karkade, agua de jamaica, or sorrel drink). Calyces are rich in citric acid and pectin, making them excellent for jams, jellies, sauces, and syrups. Young tender leaves and stems have a tart, rhubarb-like flavor and are used in salads and curries. Seeds can be roasted and eaten as snacks or ground for soups; they contain 17-20% oil. Even the fibrous root is edible, though somewhat bland and mucilaginous.

Hibiscus sabdariffa has a long history of medicinal use and is valued as an aromatic, astringent, cooling herb. The calyces contain gossypetin, anthocyanins, and hibiscin, which contribute to documented antihypertensive (blood pressure lowering) effects. Clinical studies support benefits for cardiovascular health, including reducing LDL cholesterol oxidation and improving lipid profiles. Traditional uses include treating fevers, digestive issues, kidney function, and as a diuretic. The leaves are used as an emollient and cough remedy. Seeds have laxative and tonic properties.

Beyond food and medicine, Hibiscus sabdariffa provides valuable fiber and other products. The stem fiber, called rosella hemp, is strong and durable, used for making sackcloth, twine, cord, and rope. A yellow dye can be extracted from the flower petals. Seed oil is used in cosmetics, soap making, and paint production. Flower and leaf extracts function as skin conditioners and antioxidants in commercial cosmetics. The plant is also grown ornamentally for its attractive red stems, lobed leaves, and colorful flowers and calyces.