Amaranth (Revised)

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 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).

General Information (Species account and Ecological information)

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)

A. graecizans: Is an erect, decumbent or prostrate herb usually branched from the base and often less than 40 cm high. The leaves are small. Inflorescences are green and born in clusters on the leaf axils. The seeds are tiny, smooth and shiny black.

The leaves and the young tender leaves are used as vegetable. One significant limitation is that the leaves of this species are small, and gathering a sufficient quantity for a meal is laborious and time consuming. The vegetable is often mixed with other vegetable leaves and may also be mashed with a mixture of maize and pulse among the Kamba and Kikuyu . The seed is baked into thin cakes while in some countries it is ground into flour. In East and West Africa, the plant is used to manufacture local salt.

(Maundu et., al., 1999, Maundu, P.M. & Grubben, 2004, Grubben and Denton, 2004;).

A. hypochondriacus is an annual herb growing to 2m tall or more. .Its large inflorescence is often dense and varies in colors from red to dull yellow to green. The stem is stout, and the branches are angular. The fruit is ovoid to rhombic capsule. The seeds are whitish to yellowish or blackish.

A hypochondriacus is used as a potherb, and the seed is a grain (South and Central America and Asia). The seed is pooped, roasted, or milled like maize; used to make bread in India, while in Africa, it is grown as an ornamental; recommended as a health food; it has antioxidant properties.

(Schippers, 2000, Grubben and Denton, 2004, Achigan et al., 2014).

A. hybridus Is an erect or prostrate branched herb usually 40-80 cm but occasionally attaining the height of 100 cm, especially in cultivation. The stems are green or tinted red and ridged. The leaves are simple alternate, green or tinted red. The flowers may be yellowish, green, reddish, or purple At maturity, and the entire plant may be reddish. Seeds are round, shiny black or cream. The leaves and young shoots are used as vegetable. The species is the commonest and the most widely used in the wetter regions. Much of it is picked from the wild or occasionally spared when found growing as a weed. (Maundu et., al., 1999).

A.spinosus: commonly known as spiny Amaranth, is a stout (occasionally decumbent) herb that grows to a height of about 1 m. The stems are angular, green, that may have a purple hue. It bears small green flowers that are grouped in clusters and have spines. The seeds are smooth, shiny, and reddish brown.

In tropical Africa and other regions, A. spinosus is seldom used as a leafy vegetable, picked mostly while still young before the spines have hardened. The leaves are occasionally sold in markets in Uganda and Kenya, but command a lower price than, for example, A. dubius because of its spines and unpopularity. Its use as vegetable is declining, and it is considered a food of last resort during famines.

A. spinosus is also used as forage and is said to increase milk yield in cattle. However, the spines can cause injury to the mouths of grazing animals. In Uganda, the ash of burnt A. spinosus plants is used as a tenderizer in cooking coarse vegetables and as a vegetable salt in southern Africa.

A. spinosus has numerous medicinal applications. Its root is known for its diuretic properties and is used as a decoction to treat gonorrhea in South-East Asia, The bruised leaves are considered an effective emollient in many African countries and elsewhere, and are applied externally to treat conditions such as eczema, burns, wounds, boils, earache, and hemorrhoids. When the plant's ash is mixed with Water, it is used to wash sores. A. spinosus sap is also used as an eye wash to treat ophthalmia and convulsions in children.

(P Maundu, 1999a, Jansen, P.C.M., 2004, plant@net, 2022)

A. thunbergii (Thunberg's Amaranth) is a small annual erect or ascending herb that grows to a height of about 50 cm tall. The stem can be simple or branched, angular, and almost hairless below but usually with long multicellular hairs towards the top. Flowers are unisexual and greenish in short axillary clusters. This plant is essential in Botswana, Namibia, and South Africa, where it is commonly consumed fresh or dried.

Leaves of this plant have a slightly bitter taste compared to other amaranth species. The vegetable can be eaten fresh or dried with milk or fat in combinations with maize or sorghum. The plant is also used as fodder for livestock, the ground and dried flower heads are used to make tobacco snuff milder.

(Hyde et., al, 2021, Grubben and Denton, 2004).

A. tricolor (Joseph's Coat) is a vibrant annual herb that grows to a height of 1.2 m. The plant has a sturdy, angular stem that is often highly branched. The leaves vary in color from green and purple, and in some cultivars, the foliage can be a striking combination of brilliant yellow, red, pink, or copper. The seeds are brown. The leaves are commonly cooked and cooked as a leafy vegetable, the leaves and soft stems are also eaten raw with salads. A tricolor is also used as an ornamental and the treatment of inflammations and internally as a diuretic.

(Grubben and Denton, 2004; Schippers, 2002).

A. viridis is an erect annual or short-lived perennial herb that typically grows to a height 0.5 m. Its stems are slender, branched, and angular. A viridis is considered a pan-tropical weed and has penetrated warm temperate regions worldwide. It is also a widespread weed in Africa and is occasionally cultivated. Although mostly grown as a weed, its nutritional value is high. Leaves and young plants are eaten as cooked vegetables. The plant also serves as fodder for cattle and green manure. In traditional medicine, the leaves are highly regarded for their diuretic and purgative properties, and they are used to treat a variety of ailments. (Ebert, A, W, 2011, Grubben and Denton, 2004).

Ecological information

The different species of amaranths have different altitude ranges of occurrence, with upper limit of below 2600 m. Leafy amaranths thrive in warm temperatures above 25ºC. Seeds may fail to germinate below 15ºC.

When grown under irrigation, frequent irrigation is required. The plant can tolerate drought periods once they are established, and they prefer fertile, well-drained soils that are loose and plenty of sunlight. Loam or salty-loam soils with high organic matter and good water-holding capacity are ideal for amaranths. Amaranth can tolerate a soil pH as low as 4.5.

(AVRDC, 2006, Bruce French, EcoPort).

Nutritional value information, complimentary recipes

Nutritive Value per 100 g of edible Portion

Amaranth leaves are a nutritious green leafy vegetable low in calories and fat. They are rich in essential minerals and nutrients, making them an excellent addition to a healthy diet. Amaranth leaves are an excellent source of calcium, iron, magnesium, potassium, and dietary fiber, essential for building and maintaining strong bones and teeth, regulating heart rhythm, supporting the immune system, maintaining a healthy digestive system, and preventing constipation. Additionally, amaranth leaves are a good source of antioxidants, including β-carotene equivalent and vitamin C, which help protect cells from damage, support the immune system, and aid in iron absorption.

Climatic conditions, soil and water management

Amaranth grows from sea level to 2400 m altitude. The different species may suit different altitudes. Normally the hotter it is the better it grows and it generally thrives within a temperature range of 22-30°C. A minimum temperature of 15-17°C is needed for seed germination. Amaranth is grown during both wet and dry seasons, though irrigation is normally required for dry season crops since the rate of transpiration by the leaves is fairly high. Frequent applications of water are required, related to the stage of growth of the crop and the moisture-retaining capacity of the soil. It can however tolerate periods of drought after the plant has become established. It is adapted to low to medium humidity (Bruce French, EcoPort). 

Amaranth grows best in loam or silty-loam soils with good water-holding capacity, but it can grow on a wide range of soil types and soil moisture levels. Amaranth can tolerate a soil pH from 4.5 to 8.  

Propagation and planting

Amaranth requires thorough land preparation and a well-prepared bed for good growth. Prepare 20 cm high beds during the dry season and 30 cm during the wet season using a plough. The distance between centres of adjacent furrows should be about 150 cm with a 90 cm bed top. Amaranth is planted either by direct seeding or transplanting. The choice of planting method depends on availability of seed and labour and may also vary with the growing season. Direct seeding is appropriate when plenty of seed is available, labour is limited, and during the dry season when frequency of flooding is less. Transplanting is preferred when there is limited amount of seed, plenty of labour, and during the wet season when heavy rains and flooding are most likely to wash out seeds. Raising seedlings in a nursery and transplanting them to the field shorten the crop duration in the field, and secure a better and more uniform stand especially during the wet season. 

Direct seeding 

When direct seeding is used, seeds are either broadcasted or sown in rows. Broadcast seeds uniformly at the rate of 0.5 to 1.0 g/m² of bed. Since amaranth seeds are very small, mixing seeds with sand at a ratio of 1 g seed to 100 g sand makes it easier to sow the seed and to obtain a uniform stand. Cover seed lightly with a layer of compost or rice hulls immediately after broadcasting. When plants are to be grown in rows make furrows 0.5 to1.0 cm deep and space rows 10 cm apart on the bed. Sow seeds 5 cm apart within the row and cover with a layer of compost or rice hulls. (AVRDC, 2011) 
 

Transplanting 

There are two steps to transplanting:

1. Seedling production

Seedlings are grown in a seedbed, pulled and bare-root transplanted. They can also be grown in divided trays, lifted with the root ball intact and transplanted. If seedlings are started in a raised soil bed, the soil should be partially sterilised by burning a 3-5 cm thick layer of rice straw or other dry organic matter on the bed. This also adds minor amounts of phosphorus (P) and potassium (K) to the soil, which helps in the establishment of the seedlings. Broadcast the seeds lightly in a seedbed and cover them with soil. The seeds should be one 1cm deep. Cover the seedbeds with an insect-proof net to protect seedlings from pests.

2. Setting plants into the field

Transplant in the late afternoon or on a cloudy day to minimise transplant shock. Dig holes 10 cm deep on the bed using recommended spacing for the chosen variety. Place each transplant in its hole and cover the roots with soil and lightly firm. Irrigate immediately after transplanting to establish good root-to-soil contact.

Husbandry

Amaranth is a low management crop and can grow in poor soils, but it will benefit from application of  organic fertiliser resulting in higher yield. Although amaranth is relatively drought tolerant, yet insufficient water will reduce yield. Water should be applied especially just after sowing or transplanting to ensure a good stand. As a rule, the plants should be irrigated if wilting occurs at noon. Another way to estimate soil moisture content is to take a handful of soil from the bottom of a 15 cm hole. Squeeze the soil. If it holds together when you release your grip, there is sufficient soil moisture; if the soil crumbles, it is time to irrigate. Irrigate thoroughly to maintain vigorous plant growth. Avoid over-irrigation, which may enhance disease development and nutrient leaching. Drip irrigation or micro-sprinkler irrigation is recommended in areas with limited water supply (AVRDC, 2011).

Harvesting

First harvest is at a plant height of 30 cm, about 6 weeks after transplanting. Plants may be harvested at once or leaves and tender shoots maybe harvested several times. One single harvesting is adapted for short maturing and quick growing varieties such as A. tricolor. Whole plants are pulled from soil with roots, washed and tied in bundles. With multiple harvests, young leaves and tender shoots are picked at 2 to 3 week intervals. Eventually, the plants begin to flower and develop fewer leaves. Frequent harvesting of leaves and shoots delays the onset of flowering and thus prolongs the harvest period.

Amaranth and other leafy vegetables have a large surface and loose water rapidly. To reduce water loss, harvest during the cooler time of day, such as early morning or late afternoon.  

Blanching

This is a process of briefly scalding the vegetables in boiling Water (Often salted or steaming Water for a short time). The process inactivates naturally occurring enzymes that cause undesirable changes to the vegetable leaves during preservation. Blanching helps retain the vegetable's color and texture and also cuts down the cooking time for the vegetables.

Figure 19: Blanching vegetables Ⓒ Maundu, 2006

To preserve the vegetable leaves by blanching, the following procedure may be used:

• Pick the leaves and remove the inedible portion, e.g., the stalks.
• Clean the leaves well to remove dirt and cut them roughly.
• Boil Water in a cooking pot. Use 4 liters of Water for 6 handfuls (1/2 kg) of prepared vegetables (a handful of vegetables without stalks is about 80 g).
• Place the leaves in a wire basket, a perforated blancher, or a large sieve.
• Immerse the vegetables in the boiling Water and return the Water to boil within one minute of adding the vegetables. If it takes longer to boil, the vegetables will not be firm. In the absence of a blancher, you may put the vegetables directly into the boiling Water.
• Boil for about 3 minutes. The time needs to blanch may vary with the vegetable. For soft amaranth vegetables, 2-3 minutes are sufficient.
• The properly blanched vegetable will have a bright color all the way through when sliced with a knife. If the center of the blanched vegetables remains with the raw color, the vegetable may need slightly more time in the blanching Water.
• As soon as blanching time is up, remove the vegetables and immediately put them in ice water or cold running Water. Chill them for several minutes until they are completely cold, then drain them well.
• If the vegetables had been immersed directly in Water, drain off the hot Water after blanching and immediately place or plunge the blanched vegetables into ice water or run cold Water over them. Cool as quickly as possible to prevent cooking from the residual heat. After cooling the vegetables, drain them well using a sieve and squeeze out as much Water as possible because excess Water leads to poor-quality frozen vegetables.
• Package the vegetables in freezer bags or containers for freezing. Blanched vegetables may also be stored in the air for a few days.

Markets

Amaranth is gaining popularity as a highly nutritious food, and there is a growing market for both its leaves and grains. The market for amaranth leaves is growing as more people become aware of their health benefits and culinary uses. Vegetables destined to the market need to be clean, with minimal or no insect punctures, without live insects, soft and not wilted. In countries such as Kenya, Tanzania, Uganda and Nigeria amaranth leaves are important cash crops for smallholder farmers. In Kenya the vegetable leaves are slowly finding their way to supermarkets, grocery stores and high end hotels. In addition to being sold fresh, amaranth leaves can also be found in frozen canned, or dried form in various grocery stores and markets. The demand for dried amaranth leaves is increasing due to their longer shelf life.

Until recently, grain amaranth was not a popular crop in Africa. More recently, farmers have taken the growing of grain amaranth more seriously and are supplying millers and supermarkets in Zimbabwe, Kenya, Uganda, and Ethiopia. The Amaranth seeds are popped like popcorn or ground into flour, usually used to enrich other flours. The seeds can be germinated into nutritious sprouts. The Amaranth flour is a versatile ingredient that can be used to create a variety of baked goods, including bread, cakes, muffins, pancakes, cookies, noodles, pastas, and crackers. The demand for amaranth products is expected to be fueled by health-conscious consumers who are seeking healthier, more nutritious, and gluten-free food options. The USA, Mexico, Europe, and the Asia Pacific regions are predicted to be major markets for amaranth.

Fresh Quality Specifications for the Market in Kenya