Common Name: Thunberg's Pigweed

General Information

Amaranthus thunbergii is an erect or ascending, annual plant growing around 50cm tall. The stem can simple or branched[],
The edible leaves and seeds are sometimes gathered from the wild and used locally. They are a popular vegetable in Botswana and also among the Asian population living in South Africa, where the leaves are sometimes sold in local markets[],

Known Hazards

No members of this genus are known to be poisonous, but when grown on nitrogen-rich soils they are known to concentrate nitrates in the leaves. This is especially noticeable on land where chemical fertilizers are used. Nitrates are implicated in stomach cancers, blue babies and some other health problems. It is inadvisable, therefore, to eat this plant if it is grown inorganically.

Botanical References

Range

Eastern and southern Africa - tropical areas from Congo to Ethiopia, Eritrea and Somalia, south to northern S. Africa.

Habitat

Waste and disturbed ground as a weed of cultivation, overgrazed areas, open woodland, frequently where irrigated or in seasonally wet areas along river banks, lake shores, apparently always on light soils (sand, loam ); from sea-level to 1,400 metres[]

Properties

Edibility Rating
Other Uses Rating
Habit	Annual
Height	0.50 m
Growth Rate	Fast
Pollinators	Wind, Self
Self-fertile	Yes
Cultivation Status	Wild

Cultivation Details

Prefers a well-drained fertile soil in a sunny position[]. Prefers light soils[].
The plant grows quickly from seed - young shoots can be harvested from the wild three weeks after the rains have started, whilst repeated harvesting stimulates the growth of new shoots[].
Plants are particularly susceptible to attacks by leaf-chewing insects[].
Plants should not be given inorganic fertilizers, see notes above on toxicity.
Most if not all members of this genus photosynthesize by a more efficient method than most plants. Called the 'C4 carbon-fixation pathway', this process is particularly efficient at high temperatures, in bright sunlight and under dry conditions[].

Edible Uses

Leaves - cooked[]. A somewhat bitter flavour compared to many other species in the genus[]. It is used as a spinach, eaten with milk or fat in combinations with sorghum or maize, or eaten with a porridge of pearl millet[].

Seed - cooked. Very small and fiddly, but the seed is very nutritious. The seed can be cooked whole, and becomes very gelatinous like this, but it is rather difficult to crush all of the small seeds in the mouth and thus some of the seed will pass right through the digestive system without being assimilated[].

Medicinal

None known

Other Uses

Yellow and green dyes can be obtained from the whole plant[].

Propagation

Seed - sow late spring in situ. An earlier sowing can be made in a greenhouse and the plants put out after the last expected frosts. Germination is usually rapid and good if the soil is warm[], but poor germination rates are experienced in cool or cold soils[]. A drop in temperature overnight aids germination[].
Cuttings of growing plants root easily[].