Common Name: Purple Amaranth

General Information

Amaranthus cruentus is a fast-growing, vigorous, erect annual plant. The branched stems, which are topped by terminal spikes of flowers, can grow up to 2 metres tall[].
The plant has a long history of cultivation for its edible leaves and seeds in the Andes, and is still sometimes grown as a food crop. It is a major leaf crop in parts of Africa, where it is sold in local markets and is also canned and sold in supermarkets[, ]. It is often grown in gardens as an ornamental, there are some forms with large, bright-red inflorescences that are particularly used like this[].

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

Original habitat is obscure, it was probably tropical America.

Habitat

Not known in a truly wild situation.

Properties

Weed Potential	Yes
Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Annual
Height	1.00 m
Pollinators	Wind, Self
Self-fertile	Yes
Cultivation Status	Cultivated, Ornamental, Wild

Cultivation Details

The plant can be cultivated from the tropics to the temperate zone. It grows best in areas where annual daytime temperatures are within the range 22 - 28°c, but can tolerate 10 - 45°c[]. It can be killed by temperatures of 4°c or lower[]. It prefers a mean annual rainfall in the range 2,000 - 2,400mm, but tolerates 500 - 4,000mm[].
Prefers a well-drained fertile soil in a sunny position[]. Requires a hot sheltered position if it is to do well[]. Prefers a pH in the range 5.5 - 7, tolerating 4.3 - 7.5[].
Often cultivated as a food crop and ornamental plant, it has escaped from cultivation in many areas and become naturalised as a weed of cultivated and disturbed ground[].
A fast-growing plant, the first crop of leaves can be harvested in 30 - 50 days from sowing the seed, and the plant can carry on being harvested for up to another 250 days[].
Grain yields usually range from 800-1200 kg/ha but with the use of fertilizers the yield can be raised up to 3 t/ha.
This species is cultivated for its edible seed in many parts of S. America and in Japan[, , ]. There is at least one named variety, 'Oeschberg' is a very productive plant, growing 1 metre tall and can yield up to 2.5 tonnes per hectare[]. This species is the most adaptable of the grain amaranths, it also flowers under a wider range of daylength hours than the other species[].
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 as a spinach[]. The mild-flavoured leaves are rich in vitamins and minerals[]. A good source of vitamins A & C, iron and calcium[].

Seed - very small but easy to harvest and very nutritious. They are eaten cooked or ground into a powder and used for making cakes etc[, ]. They can also be sprouted and used in salads[]. 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[].

The flowers are used as a food colouring in ceremonial maize bread[].

Medicinal

The plant is diuretic[]. It is used as a tapeworm-expellant[].
Water from the macerated plants is used as a wash to treat pains in the limbs[].

The roots are boiled with honey and then used as a laxative for infants[].

The ash from the stems is used as a wound dressing[].

The heated leaves are applied externally on tumours[].

Other Uses

Yellow and green dyes can be obtained from the whole plant[].
A red dye is obtained from the inflorescence of red forms[].

The dried plant is burnt as a source of potash[].

Propagation

Seed - can be sown in situ or in a nursery seedbed and then transplanted to their permanent position 2 - 3 weeks later[]. 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[].

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