Herb Research Foundation

BOTANICAL DESCRIPTION

Hibiscus sabdariffa is a member of the Malvaceae family. It is an annual herb that grows to 6 feet or more, stems are glabrous; lower leaves are ovate with the upper leaves being 3-5 palmately lobed. The flowers are axillary or in terminal racemes, the petals are white with a reddish center at the base of the staminal column, the calyx enlargens at maturity and the fruit is fleshy and bright red. It is known as roselle (English), l'oiselle (French), jamaica (Spanish), karkade (Arabic), bissap (Wolof) and dâ (Bambara) among other names.

The calyces are used to make cold and hot beverages in many of the world's tropical and subtropical countries. In China the seeds are used for their oil and the plant is used for medicinal properties. The leaves and powdered seeds are eaten in West Africa.

HIBISCUS PRODUCTION

Environment

Hibiscus is quite hardy and grows well in most soils that are well drained. It tolerates poor soil, and is often grown as a supplemental rather than a primary crop. It requires 4-8 months with nighttime temperatures not below 21^oC. In addition, it requires 13 hours of sunlight during the first 4-5 months of growth to prevent premature flowering.

Hibiscus requires a monthly rainfall ranging from 5-10" in the first 3-4 months of growth. Dry periods can be withstood and are desirable in the last months of growth. Rain or high humidity during the harvest time and drying can downgrade the quality of the calyces and reduce the yield.

Planting

Hibiscus sabdariffa is very sensitive to changes in the length of day. This photoperiodic quality of blooming, when the days become shorter, require the planting time to be set according to the day length and not according to the rainfall requirements.

Hibiscus is a deep-rooted crop so deep plowing is recommended in preparing the seedbed. To produce a large calyx 1,000-2,000 pounds of manure are added per acre.

Seeds are planted at a rate of 6-8 pounds or less per acre approximately + inch deep. Seeds are best planted at the beginning of the rainy season, 2-3 feet between rows and 18-24 inches within the rows. The reduced planting rate produces a larger calyx.

Planting can be done with a modern grain drill and then later requires thinning by hand, or by seed can be hand-planted. A good alternative tool would be a corn planter small enough to accommodate the hibiscus seeds.

There are over 100 cultivars or seed varieties of Hibiscus sabdariffa. The major commercial varieties are those grown in China, Thailand, Mexico and Africa, principally Sudan, Senegal and Mali.

Natural Enemies

Major diseases of hibiscus are mostly stem and root rot. Prevention techniques can include monitoring water in an irrigated field as well as avoiding the planting of crops that are also prone to these diseases. Damage done to hibiscus by insects is minor but it does exist. In the order Coleoptera is the stem borer and flea beetles, Podagrica spp. In the order Lepoptera, the abutilon moth, the cotton bollworm, and the cutworm. The order Hemoptera is a minor problem, the mealy bugs and the leafhopper, and finally in the order Hemiptera the cotton strainer.

Plant enemies usually do not compete in a cultivated field. Weeding can increase yield and calyx size, but may also reduce profit for the farmer. Because of differences in available land and labor prices, Chinese hibiscus fields are generally weeded and even hand watered if necessary, for maximum yield, while those in Thailand are given minimal attention. Quality is comparable.

Growth

Flowering of the hibiscus is induced as the days become shorter and light intensity reduces. Flowering begins in September or later depending on the country in question, and continues through October or later when the entire field is in bloom. Flowers begin to drop at the end of October or later. The seed pods begin ripening towards the bottom and proceed to the top. In Sudan, growers will sometimes allow the seed to completely ripen and the leaves drop prior to harvest.

Harvest

The harvest is timed according to the ripeness of the seed. The wet red fleshy calyces are harvested after the flower has dropped but before the seed pod has dried and opened. The more time the capsule remains on the plant after the seeds begin to ripen, the more susceptible the calyx is to sores, sun cracking, and general deterioration in quality. All harvesting is done by hand. Special care must be taken during harvesting operation to avoid contamination by extraneous material. At no time should the calyx come in contact with the ground or other dirt surfaces. Clean bags or containers should be used to transport from the field to the drying location.

In addition to avoiding contamination, the time between harvest and drying should always be kept at a minimum. Different harvesting methods are in use today. In Mexico the entire plant is cut down and taken to a nearby location to be stripped of the calyces. In China only ripe calyces are harvested with clippers leaving the stalks and immature calyces to ripen in the field. The field is harvested approximately every ten days until the end of the growing season. The calyx is separated from the seed pod by hand, or by pushing a sharp edged metal tool through the fleshy tissue of the calyx separating it from the seed pod.

Drying

Drying can be accomplished by different methods. Drying with adequate ventilation, using woven nylon mats for example, prevents sun baking, which can reduce quality. A clean sheet of plastic placed on the ground can also be used with the hibiscus spread thinly on top. This method is still prone to insect infestation and mold. Spreading the calyces on screens or frames would improve ventilation further and reduce drying time. Such frames could also be stacked or hung in a well ventilated building. Drying the calyces in forced air dryers would be costly and is rarely done. If heated drying methods are used, care must be taken so that the temperature does not exceed 43^oC.

Yield

Total yield averages 250 K per hectare, but yields up to 500 K per hectare have been reported. The drying ratio is 10:1.1. That is, for every 100 pounds of fresh calyx, 11 pounds of dry calyx is produced.