Pigweed (Amaranthus) is Africa’s most nutritious leaf vegetable. Archaeological investigations have revealed its use as

a valuable source of food by humans in Africa and the Americas for thousands of years. The various species of Amaranthus remain an important cultivated leaf vegetable in the lowland tropical areas of Africa and Asia. Yet today in most parts of the world the hardy, ubiquitous pigweeds are regarded as nuisance weeds. Their once important role in our diet has been largely superseded by the more familiar, more appealing, but far less nutritious, introduced vegetables we see in shops and grow in our gardens.

Scientific investigations of traditional food plants have revealed the value of the humble pigweed and there has been renewed interest in its potential for sustainably helping solve rural Africa’s nutritional deficiency problems. Easy to grow, easy to harvest, easy to cook, one serving of pigweed leaves as a ‘spinach’ side-dish will provide five times the iron you need, twice the calcium, 20 times the vitamin A and nearly half of your daily protein requirements.

Where do we find pigweed?Pigweeds or amaranths are found throughout Africa and the rest of the world, many of them with edible leaves and roots

and some with seeds Large enough to be harvested and utilized as ‘grain’ food. Many of the more important amaranth species harvested in the wild or cultivated for food originated from the Americas but have become cosmopolitan. Many are regarded as weeds such as the very widely distributed A. hybridus, originally from central America, but found in Africa literally from Cape to Cairo.

The most widely cultivated leaf-vegetable species in Kenya and Uganda is A. blitum (the red-leaved form is called ‘bbuga’ and the green-leaved form, ‘dodoo’). It is believed to have originated in the Mediterranean region but spread to Asia and southern Europe where it has been cultivated for the past 400 years. It was once widely cultivated in West Africa but is now less commonly grown there.

What does it look like?Amaranthus hybridus is a multi-branched erect herb growing up to 1 m high with grooved, smooth green (intruded by red) stems. Leaves are green, simple, alternate, elongate ovate, and apically-tapered. The plant bears a profusion of elongate terminal and axial cat’s tail-like flower-heads densely packed with flowers between December and May. Dioecious, with the small male (staminate) flowers born at the tips of the inflorescences, the larger female (pistillate) flowers awn-like, spreading bracteoles packing the rest of the inflorescence (flower-head). Seeds are small, shiny, and black.

Ecology and pestsAmaranths grow well in heat and sunlight and, being C4 plants, can cope with a variety of moisture regimes from tropical wet to near aridity, but have poor frost-resistance.

The larvae of several species of the small Casebearer Moths (Coleophoridae) feed almost exclusively on amaranth leaves, initially as leaf miners, and then constructing a protective case of debris and excrement. In moister areas in Central and West Africa, fungal wetrot can be a problem for young plants. Apart from some leaf feeding by a variety of insects, amaranths appear to be remarkably little-affected by pests and A. cruentus has shown marked resistance to root-knot nematodes.

Despite the nutritional value of amaranths, a number of species pose a serious weed problem to commercial crops.

Traditional and future usesAll pigweed species, being rich in proteins as well as trace elements and minerals, provide a valuable source of nutrition whether harvested from the wild or cultivated as a leaf vegetable. They continue to be widely used for ‘spinach’ in rural Africa, Asia and central America.

Pigweedby Phakamani Xaba, SANBI, Kirstenbosch National Botanical Garden and Peter Croeser

Pigweed (Amaranthus hybridus) growing in the Kirstenbosch’s Traditionally Useful Plants Garden. Photo: Phakamani Xaba.

This is the fourteenth in a series of articles on indigenous plants that have traditionally been used by humans in southern Africa for food, medicine, crafts and charms. Some of these plants are now threatened while others that once formed an important part of our diet have been forgotten. It is hoped that these articles will help revive an interest in growing, using and conserving a valuable indigenous resource. Please note that cited traditional information about medicinal use of plants does not constitute a recommendation for their use for self-treatment. Improper or uninformed use of wild plants can be extremely dangerous.

Micronutrients beneficial to humans include carotene, Vitamins A and C, iron, and calcium. Red-leaved amaranths are also rich in anthocyanins.

Excessive consumption (i.e. more than 100  g of prepared leaf ‘spinach’ a day) can have deleterious effects, however, as the leaves contain oxalates which can bind calcium. The plants are also considered toxic to grazing ruminants such as cattle because of a microbial change in the rumen which converts harmless nitrate in the grazed leaves to toxic nitrites.

Commercial aspectsLarge-scale commercial cultivation of amaranths in Africa is only partly for local consumption. The bulk is processed for export to developed first world countries as a high-demand health food.

The resistance of A. cruentus to soil nematodes allows it to be grown in both East Africa and West Africa as a year-round monoculture without crop rotation.

The climate and soils of Africa are highly suitable for growing selected amaranth species as a leaf vegetable (fresh, dried or canned) and as a nutrient-rich grain, particularly the large-grain species such as the now pan-tropical A.  cruentus and the closely-related ornamental Prince of Wales Feather (A. hypochondriacus) and the plumed A. caudatus.

Amaranths are considered by many specialists as the African food crop of the future, both for their leaves and their grain. Their C4  photosynthesis biochemistry ensures

a remarkable production yield under high light conditions. Amaranths are easy to grow, easy to harvest and produce abundant viable seed.

Seeds are available from the Kirstenbosch Seed Room. Contact Mr Khuphumla Zenze, Seed Room, Kirstenbosch National Botanical Garden, Private Bag X7, Claremont, Cape Town, 7735. Tel +27 (021) 799 8624, Fax +27 (021) 762 8239, email: seedroom@sanbi.org.za.

ReadingGrabandt, K. 1985. Weeds of crops and gardens in southern Africa. Ciba-Geigy & Seal Publishing, Johannesburg.

Pooley, Elsa, 1998. A field guide to wild flowers of Kwazulu-Natal and the Eastern Region. Natal Flora Publications, Durban.Quin, P.J., 1959. Food and feeding habits of the Pedi. Witwatersrand University Press, Johannesburg.Schippers, R.R. 2000. African indigenous vegetables: An overview of the cultivated species. Natural Resources Institute, University of Greenwich.Van Wyk, B-E, & Gericke, N., 2000. People’s plants: a guide to useful plants of southern Africa. Briza, Pretoria. Van Wyk, B-E., Van Heerden, E. & Van Oudtshoorn, B. 2002. Poisonous plants of South Africa. Briza, Pretoria.

ACTIVITYENVIRONMENT REQUIRED

FOR SUCCESSTREATMENT TIME REMARKS

Sowing Sow seed in trays using a well-drained, loamy media.

Seeds are long lived and hardy. Water the seed tray once a day or assess according to the wetness of the media. Seedlings can be treated for damping-off using any commercially available fungicide.

Sowing should be done in early spring (September) to January. The tray should be in a warm sunny area so as to hasten the germination.

When conditions are optimal, seed germination occurs within five days of sowing. Plants can be transplanted within two weeks.

Cultivation When transplanting seedlings after two weeks germination, beds should be weed-free and composted. Plant out in prepared beds in full sun, with 0.5 m spacing between seedlings.

Water initially every day for three days to compensate for transplant shock, then every second day for two weeks, then every third or fourth day.

Plants will mature within five weeks. Seedlings are vigorous growers and will out-compete weeds.

Harvesting and storage of seed

After two weeks of flowering the flowering stalk should be inspected for developed seed that is matured. Matured seed is very small, pin-head size, and black in colour. The flowering stalk can be harvested.

Flower stalks can be dried in the sun for a week then put into storage.

Seed starts appearing within five weeks from germination date.

Seed can be cleaned by rubbing the dry flower stalks against each other until the small black seeds are visible. A fine mesh sieve can also used to clean the seeds, by rubbing the flower stalk against it. Cleaned seed can be stored under cool, dry conditions until needed. Wear leather gloves as the process can be rough on the hands!

PIGWEEDAn easy guide to growing

WHaTS in a naMe?

Botanical name: Amaranthus hybridus (L.) subsp. hybridus. Amaranthus hybridus was first described by Linnaeus in volume 2 of the Species Plantarum in 1753. (Amaranthus from the Greek amarantos meaning never-fading [referring to the flower] and hybridus from the Latin hybrida, literally meaning mongrel, referring to the variability of the species and the possibility that it had resulted from cross-breeding). To the Ancient Greeks the long-lasting amaranth flower was a symbol of never-fading youth, or immortality (hence its generic name), and was celebrated as such in their poetry, plays and songs. Of the 22 species and subspecies of Amaranthus recorded from South Africa, only eight are indigenous, the rest being introduced weeds. The most common in southern Africa are the two prostrate to semi-erect pigweeds - Perennial Pigweed ( A. deflexus) and the indigenous Red Pigweed (A. thunbergi), and the erect, multi-branched annual pigweeds - Common Pigweed (A. hybridus) and Spiny Pigweed (A. spinosus) so-named

because of its paired, sharp, 2 cm spines. Worldwide there are some 70 species in the genus Amaranthus. Many amaranths have become cosmopolitan and have been so widely cultivated in the past that the genus is difficult to separate into species because of variability, hybridization and the wide variety of different ‘forms’. This includes the A. hybridus complex of central American origin to which the most widely-cultivated amaranth in Africa north of the equator, A. cruentus, belongs.

Family name: Amaranthaceae (amaranthus family). With the recent inclusion of the former Chenopodiaceae, the Amaranthaceae now contains about 160 genera and 2400  species of mostly herbs or shrubs of the tropical and subtropical regions of the world.

Common names: Amaranth, Common Pigweed (English); Misbredie (Afrikaans); Marogo, Tepe (Sotho); Thepe (Tswana); Serepelele, Theepe (Pedi); Umfino, Umbuya, Utyutu (Xhosa, Zulu).

gardening with tradit ional ly useful indigenous plants

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