Amaranth

General Information and Agronomic Aspects

Introduction

Amaranths are among Africa's most popular and most nutritious leafy vegetables. Some are also an important source of nutritious grain. Amaranths consist of 60–70 species worldwide, many of which have edible leaves. About a dozen species are important in Africa, as leafy vegetables, grain and ornamentals. Many species are originally from tropical America. Although several species are often considered weeds, the tender shoots and leaves are harvested in both wild and crop fields and are increasingly being cultivated for both home consumption and markets. Amaranth is a promising crop mainly due to its tolerance to heat, pests and diseases and the high nutritional value of both seeds and leaves. 

Amaranth is a nutritious plant rich in micronutrients. The leaves are often cooked with coarser vegetables like cowpeas to soften them or bitter vegetables, such as spider plants, African nightshades and bitter lettuce to modulate their flavour. In dry regions, the leaves are dried and ground to powder for us   e in sauces during the dry season. Amaranth grains are also considered a good source of essential minerals like calcium, magnesium, iron, and zinc. The grains are mainly obtained from Amaranthus hypochondriacus and some forms of A. cruentus. The seeds may be made into pop-cereal or milled to make flour that is incorporated into various products such as cereal flours. In Ethiopia, the grains are used in brewing alcoholic beverages.

While amaranths are not commonly used as medicine, some of the species have been used to treat various ailments in traditional medicine. Some forms of amaranths can also be used to produce yellow and red dyes for coloring foods and medicines. Some types, like Amaranthus tricolor are also grown as ornamentals because they have big, bright red leaves and flowers.

(Source: Maundu et al., 2009, Grubben and Denton, 2004, Ebert et al., 2011, Trucco and Tranel, 2011, Schippers, 2000; Van Wyk and Gericke, 2000; Rensburg et al., 2004).

Varieties 
The genus Amaranthus, commonly known as the amaranths, is a resilient group of plants distributed widely throughout Africa. Members can be found in various habitats, including cultivated fields, disturbed areas and the wild. With over a dozen species occurring in Africa, some are native to the continent, while the majority have been introduced from other regions, particularly the Americas. Some native species such as A. sphaganiocephalus (Maasai amaranth), found in East Africa, have a limited distribution. On the other hand, some introduced species like A. cruentus are more aggressive and have a wider distribution.

Most members of the genus Amaranthus that are found in Africa have monoecious flowers, meaning that individual flowers can be either male or female, but both sexes are found on the same plant. The flowers are primarily wind-pollinated, contributing to their wide distribution in different habitats. The following are the main amaranth species used in Africa.

1. Amaranthus blitum probably originated is tropical Africa and the Mediterranean region. It is naturalized in other parts of the world, from the tropics to temperate climates. In Africa, it is found in many countries with humid or sub-humid climate, mainly from mid to high altitudes. It occurs in cultivation and less often in the wild. It is cultivated in Central Africa (Cameroon) and East Africa (Kenya (Nyanza, South Rift and Western regions), Uganda and Tanzania).

2. Amaranthus caudatus originated from the central and northern Andes. It had long been grown as a food crop in the Andes, e.g., by the Incas, and the most significant genetic variation occurs in this area (Ecuador, Peru, Bolivia, and Argentina). In Africa, the distribution of A. caudatus is less documented as it has often been confused with other amaranthus species. The brightly colored types are often grown as ornamentals, mainly outside Africa.

3. Amaranthus cruentus is widespread in tropical Africa. It is originally from Central America and Mexico. It is a major leafy vegetable in parts of West Africa (southern Nigeria, Benin, Togo, and Sierra Leone) and in Central and East Africa. Grain types of A. cruentus are common in Central America and northern South America, India and Nepal but also commercially grown warmer, drier areas of the United States, Argentina, and China.

4. Amaranthus deflexus or deflexed amaranth (meaning bent downwards) is uncommon in the region but has been sighted particularly in Southern Africa. It is originally from South America.

5. Amaranthus dubius is widespread throughout most warm, humid, and sub-humid tropical Africa. It originates from tropical America, where it is common in the Caribbean region and from southern Mexico to northern South America. The cultivated type may have been developed from a weedy ancestor in tropical Asia (Indonesia, India). Amaranthus dubius is widely cultivated in West, Central, East, and Southern Africa. It is particularly important on the east coast of Africa, where it grows spontaneously in crop fields and is preserved for use as a vegetable.

6. Amaranthus graecizans occurs naturally throughout tropical Africa in sub-humid and dry areas. It is also distributed in southern Europe, tropical and subtropical Asia and was introduced to the United States. It is mainly collected in the wild as a vegetable in parts of Kenya, Uganda, Tanzania, Malawi, and elsewhere in southern Africa. It is especially popular shortly after the start of the rainy season before seeds develop. It is locally cultivated on a small scale in home gardens, e.g., by the Acholi people in Nebbi, Uganda, and in parts of Tanzania for the market.

7. Amaranthus hybridus sub-species hybridus is common in mid to high altitudes in Africa. It is common in crop fields.

8. Amaranthus hypochondriacus originates from central Mexico. It is now widely cultivated worldwide, including in tropical Africa, where it is mainly grown for its vegetable and grain.

9. Amaranthus retroflexus is only occasional in parts of Africa. The red-rooted Amaranth, as it is commonly called, is native to North America. The inflorescence has a spiny appearance like that of A. hybridus spp. hybridus.

10. Amaranthus sparganiocephalus is found in semi-arid to semi-humid areas of Eastern Africa and the Arabian Peninsula. It is common in mid-altitudes. 

11. Amaranthus spinosus probably originated from tropical South and Central America but is now widely distributed in the warmer parts of the world, including tropical Africa, where it mainly occurs as a weed and in disturbed open places. It is not normally cultivated, but in crop fields, a few plants may occasionally be preserved as a source of vegetables.

12. Amaranthus thunbergii is native to Southern Africa but grows as far north as the Congo and the Horn of Africa. It mainly occurs in open places in the wild but also as a weed in cultivated land. It is now found as a weed in Australia and Europe.

13. Amaranthus tricolor originates from tropical Asia, where it is one of the important leaf vegetables. A. tricolor is not a competitive weed and therefore it is a rare exotic vegetable in Africa. It is occasionally cultivated in cities as an ornamental.

14. Amaranthus viridis is possibly of Asian origin but is now a cosmopolitan weed in the tropics and subtropics of the world. In tropical Africa, it is common in cities and roadsides. It is occasional in crop fields.

(Sources: Maundu, P. 1999; Ebert, A, W, 2011; Grubben and Denton, 2004; Achigan et al., 2014; Ebert, A.W., 2011).

Species accounts

Amaranths are often challenging to identify taxonomically due to their close resemblance and the presence of intermediaries. The small seeds are easy dispersed and so species may often occur where they are not expected. Easy morphological features to check include plant growth habit, stem and leaf coloration, mature plant height, the shape of the leaves and the inflorescence. The seeds are usually shiny black or brown but may be cream in edible grain types. The following are some of the more common amaranths.

Amaranthus blitum is a branched, erect, ascending or prostrate herb that grows to nearly 1.2 m in height, but usually smaller, around 30–60 cm, in cultivation. Its stems are usually green to brown, occasionally reddish in color. The leaves are typically green, sometimes with a slight brown tinge. The flowers are borne in axillary and terminal spikes. The seeds are conspicuously larger compared to other species of amaranth, with approximately 100 seeds per gram.

A. blitum is used as a leaf vegetable in many African countries. It is highly regarded for its soft texture. It is often recommended for young children, lactating mothers and people who are anaemic. The plants are eaten by livestock but sparingly.

(Sources: Maundu et al., 1999; Burkill, 1985; Achigan et al., 2014; Grubben & Denton, 2004).

Amaranthus cruentus is an annual herb grown for grain production (pseudocereal), as well as a leafy vegetable and ornamental. The plant can grow to a height of 1-1.5 m high, sometimes even higher. The crop is characterized by its fast growth, ribbed, straight stems, large pointed leaves, and a conspicuous terminal inflorescence with a prickly appearance. The inflorescence may vary in color from green to red or purple and sometimes a mixture of these colours. The seeds are usually dark brown to black, but can also be white to cream or golden in grain amaranths. Ornamental types of A. cruentus have large bright-red inflorescences and are often found in the tropics and subtropics. These inflorescences can be used to produce a red dye. In tropical Africa, A. cruentus is grown as a highly productive, nutritious and economically important leafy vegetable. The young leaves and tender stems are commonly harvested and cooked or fried, and served as a side dish. 
(Achigan et al., 2014, Maundu, 1999; Grubben and Denton, 2004; Wolosik et al., 2019. Chaney, 2021; Ebert, A.W., 2011).

Amaranthus dubius is an erect herb that grows to a height of 1 m or more. The stems are ridged, highly branched, and usually green or tinged purple. The leaves are simple, usually with an ovate leaf blade to 8 cm long, veins conspicuous underneath. The flowers are borne in clusters, in the axils and in terminal branched heads or spikes. Fruits are covered by bracts and bracteoles which are the more visible structures of the flowering part. Seeds black, shiny.

The leaves and tender shoots are used as vegetable, sometimes cooked with more bitter vegetables such as spiderplant, african nightshade and bitter lettuce. The plant is grown commercially for city markets, especially in East Africa. This species is now widely grown for its leaves and is also a common plant in disturbed areas, cities, and riverine environments

Used for children and lactating mothers, treating fever, hemorrhage, anemia and stomach ache.

(Grubben and Denton, 2004; Schippers, 2000, Maundu, P.M, 1999, Achigan et al., 2014)