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gardening with traditionally useful indigenous plants
Pigweed (Amaranthus hybridus) growing in the Kirstenbosch’s Traditionally Useful Plants Garden. Photo: Phakamani Xaba.
Pigweed
by Phakamani Xaba, SANBI, Kirstenbosch National Botanical Garden and Peter Croeser
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.
P
igweed (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has been largely superseded by the more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.
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VELD&FLORA | DECEMBER 2010
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’ sidedish 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 leafvegetable 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 pests
Amaranths 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 littleaffected 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 uses
All 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.
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 aspects
Large-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 highdemand 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
An easy guide to growing
ACTIVITY
ENVIRONMENT REQUIRED
FOR SUCCESS
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 neverfading [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 neverfading 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
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: [email protected].
Reading
Grabandt, K. 1985. Weeds of crops and gardens
in southern Africa. Ciba-Geigy & Seal Publishing,
Johannesburg.
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).
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.
PIGWEED
TREATMENT
TIME
REMARKS
Sowing
Sow seed in trays using a welldrained, 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 dampingoff 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
Seed starts appearing within five weeks from
the sun for a week then put into germination date.
storage.
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!
DECEMBER 2010
| VELD&FLORA
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