This species is treated here in a narrow sense, excluding Hibiscus asper which is treated as distinct[].

Common Name: Kenaf

General Information

Hibiscus cannabinus is an unbranched or branched, erect, annual to perennial plant; normally single-stemmed, it usually grows around 1.8 metres tall, though some selected cultivars can be up to 5 metres. The stems can become more or less woody and persistent[, , , ].
A multipurpose plant, providing food, medicines and a range of commodities. Kenaf has been cultivated for 6,000 years as a fibre crop in Africa and the plant is now widely cultivated in tropical and sub-tropical areas of the world, for its fibre, as an oil crop and also as a food crop and medicinal plant. Both the fibre, and the oil obtained from the seed, are traded whilst the edible leaves are sold in local markets[, , ].
Often found as a weed of cultivated crops within its native range, it has the potential to spread as a weed in other suitable areas[].

Known Hazards

None known

Botanical References

, ,

Range

Original habitat is obscure, it probably arose in the tropics of Asia or America

Habitat

Not known in a truly wild situation, but the plant is found in cultivated land, old gardens, dikes between
irrigated fields, ridge tops in shallow soil, rocky fissures, talus, open grassland plains, savannash, flood plains, seasonal swamps[].

Properties

Weed Potential	Yes
Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Annual/Perennial
Height	1.80 m
Growth Rate	Fast
Pollinators	Insects, Bees
Self-fertile	Yes
Cultivation Status	Cultivated

Cultivation Details

When cultivated, the plant is usually grown as an annual. It can be grown successfully in a wide range of climates from the temperate zone to the tropics, at elevations up to 1,000 metres. It grows best in areas where annual daytime temperatures are within the range 15 - 28°c, but can tolerate 10 - 35°c[]. It is damaged by frosts[]. It prefers a mean annual rainfall in the range 600 - 2,000mm, but tolerates 450 - 3,000mm[].
Prefers a well-drained humus rich fertile soil in full sun[]. Tolerates most soils but prefers a light sandy soil[]. Plants are adapted to a wide range of soils and climatic conditions[]. Prefers a pH in the range 6 - 7.5, tolerating 4.3 - 8.2[]. The plant is damaged by heavy rains with strong winds[].
A fast-growing plant, the first harvest of its leaves can take place within a month of sowing, whilst the fibre can be ready to harvest in 3 - 4 months[, , ].
Yields of fibre can be 1 - 6 tonnes per hectare[].
Yields of leaves can be 20 - 30 tonnes per crop per hectare when the plants are uprooted, or up to 60 tonnes if the plants are harvested as cut and come again[].
Annual seed yields can be about 350 - 400 kilos per hectare[].
Plants are daylight sensitive, they remain vegetative and do not flower until the daylength is less than 12.5 hr/day. Two weeks of very cloudy days will induce flowering as daylength approaches 12.5 hr[].
The plant has a deep-penetrating taproot with deep-seated laterals[]. Plants are highly susceptible to root-knot nematodes[].
Kenaf is mainly an out-breeding plant, but up to 30% self-pollination occurs[, ].

Edible Uses

Shoots and young leaves - cooked[, , ]. Used as a potherb or added to soups[]. The leaves have an acid flavour like sorrel[].

Flowers - raw or cooked[].

Seed - roasted or ground into a flour and made into a kind of cake[, , ].

Root - it is edible but very fibrous[]. Mucilaginous, without very much flavour[].

Bark - raw[]. Children chew the bark for its sweetness[].

An edible oil is obtained from the seed[]. The refined oil is used for cooking[]. The seed contains about 20% of a first class cooking oil[]. The yield varies from 2 - 10 tonnes per hectare[] (or is it per acre?). One report says that the seed oil is considered to be inedible[].

Medicinal

The juice of the flowers, mixed with sugar and black pepper, is used in the treatment of biliousness with acidity[].

The seeds are aphrodisiac and stomachic[, ]. They are added to the diet in order to promote weight increase[]
Applied externally, the leaves are used as a poultice on pains and bruises[].

The leaves are purgative[]. An infusion of the leaves is used in the treatment of coughs[]. In Ayurvedic medicine, the leaves are used in the treatment of dysentery and bilious, blood and throat disorders.
The powdered leaves are applied to Guinea worms in Africa[].

The peelings from the stems have been used in the treatment of anaemia, fatigue, lassitude, etc[].

Agroforestry Uses:

Kenaf plants accumulate minerals such as selenium and boron, and can be used as a bioremedial tool for removing these metals from contaminated soil[, ].

Other Uses

A fibre is obtained from the stem[, ]. It is a very good jute substitute though it is a bit coarser[, ]. The fibre strands, which are 1.5 - 3 metres long, are used for making rope, cordage, canvas, sacking, carpet backing, nets, table cloths etc[, , ]. For the best quality fibre, the stems should be harvested shortly after the flowers open[, ]. The best fibre is at the base of the stems, so hand pulling is often recommended over machine harvesting[]. Yields of about 1.25 tonnes of fibre per hectare are average, though 2.7 tonnes has been achieved in Cuba[, ]. Yields of 3.5 tonnes per hectare have been achieved[]. The pulp from the stems has been used in making paper[].
The stems are usually retted in clear and slow-moving water for a period of 10 - 15 days at temperatures above 30°c to liberate the fibres from the bark[].

An extract of the whole plant is used as an ingredient in commercial cosmetic preparations as a skin conditioner[].
A powder made from the stems is used as an ingredient in commercial cosmetic preparations as a skin conditioner[].
An aqueous solution of the steam distillates obtained from the stems is used as an ingredient in commercial cosmetic preparations as an antioxidant, skin conditioner and skin protector[].

The stems have been used as plant supports for growing runner beans etc[].

The seed contains between 18 and 35% of an edible semi-drying oil[]. It is rather similar to groundnut oil, obtained from Arachis hypogaea[]. The oil is also used for burning, as a lubricant and in making soap, linoleum, paints and varnishes[, , , ]. The seed yield varies from 2 to 10 tonnes per acre[] (or is it per hectare?).

The soot from the stems has been used as a black pigment in dyes[].

The stem has been used as a base for drilling fire[].
The dried stems, after the fibre is removed, can be used as fuel[].

Propagation

Seed - sow early spring in a warm greenhouse. Germination is usually fairly rapid. Prick out the seedlings into individual pots when they are large enough to handle. If growing them as annuals, plant them out into their permanent positions in early summer and protect them with a frame or cloche until they are growing away well. If hoping to grow them as perennials, then it is better to grow them on in the greenhouse for their first year and to plant them out in early summer of the following year.
Cuttings of half-ripe wood, mid summer in a frame. Overwinter them in a warm greenhouse and plant out after the last expected frosts.