Crops, fruits, vegetables

Introduction

Vernonia amygdalina, commonly known as bitter leaf (bitterleaf) belongs to the genus Vernonia in the family Asterace

ae (sunflower family). The genus Vernonia is vast, comprising over 1000 species, among them, more than 300 species in Africa, with approximately one-third of these in Madagascar.
Four related woody species used as vegetable are known by the name bitter leaf: The common bitter leaf (Vernonia amygdalina), the sweet bitter leaf (V. hymenolepis), star-flowered bitter leaf (V. colorata) and country bitter leaf (V. thomsoniana). A fifth vegetable species, Vernonia cinerea or little ironweed is an annual commonly found in crop fields. V. amygdalina and V. hymenolepis are mainly wild but are often cultivated or preserved in cropland in West Africa. The similar looking V. colorata is less frequently cultivated and is generally found in drier areas of Africa. It is frequently consumed in the drier parts of West and Central Africa. V. thomsoniana is more commonly found in the wild particularly on highlands and is the bitterest of the five species. 
Species within the genus Vernonia are very variable and differences may not be obvious especially between V. colorata and V. amygdalina. V. thomsoniana has smaller leaves than the cultivated ones.
Vernonia amygdalina holds great culinary and medicinal significance in Africa. Despite its bitter taste, the leaves are widely used in traditional African cuisine as a vegetable and for flavoring soups and stews. The bitterness is often reduced by mixing with other vegetables like the waterleaf (Talinum triangulare). Varieties that are less bitter can be found, but are still not common. V. amygdalina is commonly found in Nigeria, Cameroon, Gabon and Congo (Democratic Republic) and to a lesser extent in their neighboring states. The Luhya in western Kenya use V. amygdalina as a vegetable, but do not cultivate it. This bitterleaf species can also be found in South-East Asia where it is similarly grown as a vegetable. Bitter leaf is a popular vegetable in West Africa. In Cameroon the species grows spontaneously all over the country.
Apart from its culinary use, Bitter Leaf has a long history of use in traditional medicine. It is believed to possess various medicinal properties, the leaves, roots, and stem, are used to treat ailments such as malaria, stomachaches, and fevers. Several countries in Africa, including Nigeria, Ghana, and Cameroon, are major producers and consumers of Bitter Leaf due to its popularity in local cuisines and traditional medicine. In the global markets, herbal medicine companies and health food stores source Bitter Leaf extracts and supplements from both local African producers and international suppliers (Ucheck Fomum, F., 2004). 

Species accounts

Vernonia amygdalina is a single-stemmed shrub to 3 m, sometimes a tree to 10 m. The much branched; stem may be up to 40 cm in diameter. Bark: Pale grey, rather rough, flaking later, branches brittle. Leaves: Ovate, up to 20 x 5 cm, tapering at both ends, dark green above, soft pale hairs below, edge may be widely toothed. Flowers: White-green, each only 6 mm across, in dense branching flattened heads to 30 cm across, sweet scented in the evening. Fruit: Tiny seeds with stiff white hairs.
V. amygdalina is easily mistaken with V. colorata in West and Central Africa. The two species are used in a similarly manner. V. amygdalina has leaves with irregular edges, dented with hairy fruits. It grows spontaneously in secondary forest. V. colorata on the contrary has leaves with regular edges with glabrous fruits. It grows in dry derived savannahs. The leaves of V. amygdalina are sometimes collected from the wild but most people prefer leaves from cultivated plants which are generally less bitter. (Stivels, 1990, Ucheck Fomum, 2004). 

Ecological conditions 

Vernonia amygdalina occurs naturally along rivers and lakes, in forest margins, woodland and grassland, up to 2000 m. It often occurs in disturbed localities such as abandoned farmland, and can be found growing spontaneously in secondary forest. It requires full sunlight in cultivation. Flowering is induced by short days. It prefers a humid environment although it is fairly drought tolerant. It can be found on all soil types, but performs best in humus-rich soils.
The species has been observed to be eaten by goats in Central Zone of Delta State, Nigeria. However, in general, it has been found that Vernonia amygdalina have an astringent taste, which affects its intake (Bonsi et al., 1995a). A mixture of Vernonia and molasses has been tried in order to make bitterleaf more palatable by animals, but 6.6 % of DM intake had to be added to improve the intake of Vernonia. During the dry period, dairy farmers in southern Ethiopia feed animals with boiled Vernonia, since the boiling decreases the content of secondary plant compounds and makes the feed more palatable. Vernonia amygdalina has also been fed to broilers, where it was able to replace 300 g kg-1 of maize-based diet without affecting feed intake, body weight gain and feed efficiency (Teguia et al., 1993 cited by Bonsi et al., 1995a).

Related species

1.     Vernonia hymenolepis can be found wild in mountainous areas in Cameroon, Uganda, Kenya, Tanzania and Ethiopia and is frequently cultivated in Cameroon where it is referred to as sweet bitterleaf. It is also called bayangi bitterleaf because of its popularity with the Bayangi people in the Manyu division of South-West Cameroon. Sweet bitterleaf is grown as an annual crop, which reaches a height of about 75 cm when grown as a kitchen-garden crop or in mixed cropping systems, whereas in the wild it can be either annual or perennial depending on the availability of moisture in the soil. In some places near streams, wild shrubs of 3 m high can be observed which are probably at least 2 or 3 years old. V. hymenolepsis is by far the least tolerant to drought. It is therefore often found in marshy areas or at high altitudes and its cultivation during the dry season requires frequent irrigation.

2.     Vernonia colorata

This is a shrub or small tree. The leaves are oval or more frequently elongated, with distinctly undulate margins. The upper surface is harshly hairy, the undersurface covered in dense woolly hairs, obscuring the net-veining. The flowerheads are star-shaped, forming large terminal clusters, mauve when young but soon turning white. Of the four frequently consumed Vernonia species in West Africa, V. colorata is most tolerant to drought (Hyde et al, 2018).

3.    V. thomsoniana is an erect slender, sparingly-branched shrub up to 3(5) m. tall. Stems may be one to several with the upper stem and branches finely ribbed and densely hairy. Leaves are 10 x 5 cm. or larger. The lower surface is soft-hairy. The species is found from sub-montane forest margins and grassland to high rainfall mixed deciduous woodland and grassland throughout tropical Africa from Guinea and the Sudan southwards to Angola and Mozambique at medium altitudes.

4.    Vernonia cinerea is an erect, branched or unbranched herb up to 1.5 m high, usually 30-100 cm. Stem with longitudinal lines, hairy. Leaves: Broadly ovate, slightly hairy, margin wavy or toothed, base flat, narrowed or rounded. Flowers: Purple or white, borne on a terminal branched inflorescence. 
The species is widespread in Africa. It is mainly found in wet areas, in grassland, roadsides, disturbed areas and cultivated land as a weed, often under trees. Commonest during wet seasons in hot low areas, 0-1,700 m. The leaves are used as vegetables among the Mijikenda groups of Kenya. Leaves are often cooked with other vegetables as by themselves, they have a strong odour. Common combinations are Launaea cornuta (mchunga), amaranths and cowpea leaves. It can be grown easily from seed. (Maundu et al., 1999).

 Agronomic aspects 

Propagation is possible by seed, but most farmers use stem cuttings selected on the basis of attributes such as degree of bitterness, leaf size and growth characteristics. In home gardens more than one type is often grown because young people prefer the less bitter types and elderly people the more bitter ones. Cuttings grow faster than seedlings. Seed may be collected from dry flower heads. Seedlings are grown under shades. Seeds are broadcasted or sown in lines spaced at 15-20cm apart. After 7 days seedlings emerge. Overcrowding will cause rotting of seedlings. When the weather is dried, watering is to be done at least once a day. Before transplanting the seedlings, leaves are tasted for their bitterness using the tongue. The seedlings are transplanted at 6 weeks old. In mixed cropping systems, seedlings are spaced 75 x 75 cm, while they are spaced at about 20 x 20 cm in monocropping. A closer spacing will reduce the vigour due to etiolation (being thin and tall) and competition for nutrients and water. In some home gardens people plant bitterleaf amongst other crops or as a hedge or live fence; in commercial fields it is planted in rows
Cultivation practices
V. amygadalina is generally multiplied by planting shoots in to the soil. Mature and young stem cuttings are used for planting. The cuttings are planted at 450 angle to foster the growth of shoots. Cuttings are selected from varieties known for their attributes. Young leaves that emerge after about three weeks are in a high demand in the market especially during drought periods.

Husbandry
Weeding, mulching and the application of organic manure in the nursery stage contribute to healthy and rapid growth of seedlings and cuttings. During the dry season bitterleaf is scarce and thus expensive at the markets and therefore irrigation is profitable. Old branches should be pruned back to a low level to stimulate the production of larger, succulent and abundant foliage. This is best done before the arrival of the rains. Some farmers deliberately prune their bushes back at the end of the rainy season and make sure that the plants receive adequate water. The young light-green sprouts with large leaves that emerge after about 3 weeks are very valuable at the market, since at that time most other leaves have turned grayish in color, are much smaller and distinctly coarser and bitter. Young plants are more productive than older ones and commercial farmers prefer to plant a new crop at the beginning of every new season or after the second year. They do not remove their old crop until they have been able to harvest the first regrowth at the start of the season because this commands a premium price.

Harvesting and post-harvest practices

Harvesting
The first harvest takes place at about 4 weeks after transplanting. Plants are ratooned at 5-10 cm above ground, when the plants are about 40-50 cm in height. This operation will enable the lateral shoots to grow and extend harvesting for 2 to 3 months. During the rainy season, harvesting takes place by cutting the leafy shoots, allowing new side shoots to develop, which can be harvested a few weeks later. Stems of various lengths are cut in the afternoon and these are sorted and tied into bundles of equal length. The bundles are kept overnight, placed upright in a basin of water and sometimes covered with jute bags to avoid desiccation. The bundles themselves are tied together into bigger bundles before they are carried to the market. During the dry periods people pick only the leaves and leave the shoots intact. Young pale green sprouts with large leaves grown under irrigation during the dry periods fetch high prices in the market, because by this time most leaves of other plants are small and very bitter.
After each harvest, urea is applied to help growth of new shoots. Contact of urea and leaves should be avoided to prevent fertilizer burn. Stems are tied in bundles whose size varies with the season. The bundle can be about 1kg in rainy season but reduces to about ½ kg during the drought period. 
Post-harvest practices
Stems of various lengths are cut in the afternoon and tied into bundles. These bundles are kept overnight, placed upright in a basin of water. Alternatively, several other bundles are tied together and sprinkled with some water ready for market. Sometimes bundles are covered with jute bags to avoid desiccation.
Leaves may be shredded and pounded in a mortar. During pounding foam develops. This foam and bitterness is removed by repeatedly rinsing the leaves with water between poundings. Leaves may be shredded and boiled first. The pounded leaves are rinsed until the water that drains off is no longer green. Alternatively, the leaves are pressed into fist-sized balls before they are marketed. People have become careful when buying processed bitterleaf because some unscrupulous traders use other plants to increase the volume. Office workers in the main cities no longer have the time to prepare bitterleaf themselves and have become accustomed to a ready-made product offered at the local markets. A more bitter product is obtained by stopping the formation of foam during pounding by adding palm oil.
In urban areas, consumers are accustomed to buying ready-made products to cook their meals. Thus there is high demand for these processed products (Schippers, 2000).

Nutritional value and recipes

The bitter taste of Vernonia amygdalina is due to anti-nutritional factors such as alkaloids, saponins, tannins and glycosides (Buttler and Bailey, 1973; Ologunde et al., 1992 cited by Bonsi et al. 1995a; Anonymous, 1999). The leaves are rich in protein, fibre, calcium, iron, magnesium, potassium, zinc, vitamin A, riboflavin, Vit B6 and folate.

Source (Nutrient data): West African food composition table (Stadlmayr, 2012)
$ Draining the water several times leaches away water soluble nutrients significantly.
a Lewis, J. 2019. Codex nutrient reference values. Rome. FAO and WHO
b NHS (refers to saturated fat)
c https://www.hsph.harvard.edu/nutritionsource/water/
d British Heart Foundation
e FDA
f NIH
g Mayo Clinic
h For pregnancy and lactation, the amount increases to 1.9 mg and 2.0 mg, respectively

Complimentary recipes
In Cameroon, bitterleaf is processed in three main ways to reduce the bitterness. Firstly, the leaves are shredded from the stems, sliced into tiny slices and then subjected to squishing and rinsing several times with cold water. Alternatively, the sliced leaves are pounded in a mortar before squishing and rinsing for those who do not want to use soda (limestone). Secondly, it can be blanched for 5-10 minutes in hot water in which potash has been added before squishing and rinsing. In all cases, the product is rinsed several times to get out the foaming greenish liquid, which is the bitter part of it. The squishing and rinsing continues until the foaming stops and the liquid from the vegetable is almost clear. Thirdly, whole leaves that are not sliced or chopped are blanched in hot water and used mostly in porridges. Seasonings of choice are used. These include seasoning cubes, green leafy species (like ground celery, basil, leeks and parsley) and pepper. Depending on the occasion ground egusi (seeds of the members of Cucurbitaceae e.g. pumpkin and gourd seeds), smoked fish or meat is added. This is served with fufu (starchy component of a meal made from flour derived from corn, yams, plantains or cassava), boiled plantains, yams, cocoyams, taro and potatoes.

1.    Nndole soup

Ingredients
1 kg beef
200 g stockfish (cut into small pieces)
1/3 cup dried shrimps
1 cup fresh peanuts (dehulled)
1 small onion
2 medium fresh round red pepper
2 cloves garlic
500 g bunch fresh bitter leaf (Vernonia amygdalina)
Salt 
(Enough for 5-6 persons)

Method
•    Clean, cut up and wash meat, season with some salt and half onion, put to boil with about 3 cups water, half way through boiling (15-20 minutes) wash stockfish and add to boiling meat, cook both until tender adding more water if necessary, remove from pot and set aside, save the meat stock
•    Wash bitter leaves, blanch peanuts, remove from heat and peel off skin, grind and set aside
•    Grind dried shrimps, then grind together pepper, garlic and the rest of the onion
•    Heat oil moderately in a pot, add ground peanuts, and the ground pepper mixture, fry for 5-7 minutes stirring constantly
•    Add stock from the boiled beef and stockfish making it up to 4 cups with water, add boiled meat and stockfish, ground shrimps and washed bitter leaves, salt to taste and stir very well. 
•    Allow to cook under low heat fro 15-20 minutes stirring occasionally
•    Serve hot nndole with boiled yam, plantain, rice or cassava.
Source: Foods of West Africa-Origin and use by Francisca Smith.

2.    Ndole (Ndunekun) and groundnut paste)

Ingredients
150 g washed bitterleaf
2 tablespoonfuls groundnut flour 
4-6 medium size smoked fish (or 1 kg beef) 
2 tablespoonfuls of cooking fat 
1 teaspoonful Salt 
3 seasoning cubes or 1 tablespoonful of curry powder 
1 chili pepper
1 tablespoonfuls of soya 
60 g onions 
1 tablespoonful ginger 
1 tablespoonful garlic 
100 g crayfish 
Green leafy species (stalks of celery, leeks and parsley), optional            

Preparation
For this dish, the preferred method of washing the bitter leaf is by using limestone, Wash dried grains of peeled groundnuts and soak in water for about 30 minutes
Boil groundnuts for 5 minutes and grind into paste and mix well 
Chop the meat into cubes and boil till tender
Remove skin and shred the fish and wash (soak fish to remove skin if tough)
Wash bitter leaf using limestone as above 
Blend the garlic, ginger, hot pepper and crayfish
Add the oil to a separate saucepan, and heat it 
Add chopped onion and shredded fish and fry till it begins to turn golden brown, and then add the groundnut paste bit-by-bit stirring all the time to ensure it does not burn. Allow to simmer over low heat for 15 minutes
Add the ground ingredients, the meat, salt and seasoning cubes, stir and cook for 10 minutes
Add the bitter leaf into the mixture while stirring, also add ground leafy species at this stage, and allow cooking for 5 minutes
Serve warm with yam, plantain, fufu or other preferred starchy staple.

Remarks:
Mature leaves are preferred as young ones are too soft. However, the mid-vein is removed to help reduce the bitterness and toughness.
Too much of either groundnut or soybean paste will dilute the recipe causing it to appear as a soup.
For this recipe soybean can replace groundnut paste in this popular dish called ‘ndole’. To prepare the soybeans, boil same number of cups of soybeans till they are cooked, i.e. soft when pressed between the fingers. When cooked remove the skin, and grind in blender. The rest of the steps as described for groundnut paste. 
The recipe could be quite bitter.
Source: Poubom CF, Ngundam, Mboussi a Messia and Simon Zok in: A Cookbook of African Leafy Vegetables. IPGRI, 2006.

3. Ndonaesaka Ndole-egusi (Bitter leaf with egusi)

Ingredients
100 g bitter leaf 
200 g beef 
3 glasses egusi 
5 tablespoonfuls cooking oil 
120 g fresh tomatoes 
4 seasoning cubes 
10 g pepper 
5 g salt 
5 g or 1 teaspoonful garlic 
50 g onion 
10 g or 1 teaspoonful ginger 
Green leafy species ( as above)            

Preparation
Shred leaves and cut into tiny slices
Add limestone to boiling water and proceed as described above 
Cut the meat into cubes. Add salt, seasoning cubes and a little water to ensure it does not stick to the saucepan and let it cook for about ten minutes or until well done 
Grind separately the pepper, garlic, ginger, crayfish and egusi then mix them together inside a pan
Heat the cooking oil in a saucepan and when hot, add the chopped onion and tomatoes and stir
Add the meat and dry fish and stir
Add ground egusi, stir and let to cook for 10 minutes 
Add the rest of the ground ingredients and stir
Add the washed bitter leaves, mix well, and cook for 10 minutes, add the ground green leafy species
Served with fufu corn, boiled yams or plantains or any other staple starchy component

Remarks
Too much egusi will dilute the vegetables causing it to loose its taste.

Source: Poubom CF, Ngundam, Mboussi a Messia and Simon Zok in: A Cookbook of African Leafy Vegetables. IPGRI, 2006.

4. Nchubekang

Ingredients
2 kg bitter leaves (2 bundles)
1 kg beef 
1 tablespoonful palm oil or another cooking oil
5 g bush onion 
4 seasoning cubes
2 teaspoonfuls salt 
1 glass cray fish 
2 g chili pepper 

Preparation
Wash the bitter leaves well and slice them 
Cut the meat into smaller pieces
Put this into a saucepan, add a little water to ensure it does not burn and steam it till it is dry of water or has become tender enough
Add salt and the seasoning cubes 
When the meat is tender add to it the bitter leaves and cook it for 20 minutes
Add the chopped bush onion, ground crayfish and hot pepper and stir
Add the oil and cook for 5 minutes
Serve with starch of choice

Remarks 
Too much onion and oil will unpleasantly alter the taste of the food.
Source: Poubom CF, Ngundam, Mboussi a Messia and Simon Zok in: A Cookbook of African Leafy Vegetables. IPGRI, 2006.

Introduction.

Brassica carinata, also known as Ethiopian kale or Abyssinian mustard, is a member of the Brassicaceae family and the genus brassica. The genus Brassica includes other essential exotic species such as cabbage, turnip, rape and swede, and kales. Ethiopian kale is believed to be native to the Ethiopian Highlands and is the African relative of kale from Europe. It has since spread to other parts of Africa and the world, including South and North America, Europe, and Asia. It is primarily grown in semi-arid regions, where its drought tolerance and short growing season make it an ideal crop.
Ethiopian mustard is cultivated as a multi-purpose crop in the Ethiopian highlands at altitudes between 1500 and 2600 meters. Several landraces exist that are used for their leaves, for their oilseed, as fodder, or a combination of these. Such landraces could be strongly branched with many small leaves, or plants could have just a few branches with larger leaves with a wide range of sizes and shapes in between.
Brassica carinata is a highly versatile plant with numerous applications. In most parts of Africa, B carinata is primarily used as a cooked leafy vegetable. The leaves and the tender stems are eaten in salads, boiled, and pickled. Despite its sharp odor, the cooked leaves have a delightful taste and are abundant in nutrients such as protein, fiber, and vitamins. The plant is often grown in mixtures of other traditional leafy vegetables and is eaten by preparing it with nightshade and spider plant.
Apart from being a food source, B. carinata is also utilized for its medicinal properties. The seeds of this plant are renowned for their efficacy in treating stomach aches, while the water used to boil the leaves is believed to have therapeutic benefits for diarrhea. Moreover, the seeds of ethiopian kale are used as a flavoring spice for raw meat in ethiopia. The seeds also contain glucosinolates that possess anti-carcinogenic properties. B. carinata has significant industrial value, as the oil derived from its seeds can be utilized to produce water repellants, waxes, and polyesters. Although the seeds of this plant contain high levels of erucic acid and glucosinolates, which are unsuitable for human consumption, they are highly productive and serve as a valuable source of animal feed.
(Maundu et al., 1999 ,Grubben et al., 2004, AVRDC & IPGRI, 2006).

Geographical Distribution

Brassica carinata is believed to have originated in Ethiopia approximately 4000 years BC, and it boasts a high degree of genetic diversity within this region. However, due to confusion in the literature regarding its distinction from Brassica juncea (L.) Czern., it is difficult to determine the exact distribution of Brassica carinata throughout Africa. The cultivation of Brassica carinata as an oil crop is restricted to Ethiopia, but as a leafy vegetable, it is often grown in East and southern Africa, less so in West and Central Africa (AVRDC & IPGRI, 2006).

Ethiopian kale is native to Eritrea and Ethiopia. It appears wild occasionally in field has been introduced in a number of African countries including: Gabon, Ivory Coast, Kenya, Tanzania, Uganda.

General information.
Species account

Brassica carinata is an erect, annual herb that grows to a height of 1.2 m or more. The stems and leaves are light green, pinnately lobed, and smaller compared to other brassicas). Flowers are yellow, borne in a long terminal inflorescence. They later bear a long green capsule that turns brown when dried and bears many small, pale to dark brown seeds, 1-1.5 mm in diameter. The time from sowing to the emergence of the Ethiopia kale seedling is about 5 days depending on the temperature and the soil moisture conditions. The plants develop an extensive rooting system. The plant sometimes occurs as a weed in cultivated areas and prefers fertile soils between 0 to 1600 m in elevation that receive 600 mm to 1600 mm of annual rainfall.
(Maundu et al., 1999, AVRDC & IPGRI, 2006).

Production of Brassica carinata for its seed is important only in Ethiopia. Production in Canada and the Mediterranean region is still experimental. As a leafy vegetable, it is mostly grown as a kitchen garden crop. However, in Tanzania, Malawi, Zambia, and to a lesser extent in Zimbabwe, it is also grown as a market crop. Its use as a leaf crop appears to decline because of higher-yielding leaf cabbage (Brassica oleracea) and leaf mustard (Brassica juncea). No statistical data on its production are known. (AVRDC & IPGRI, 2006).

Ecological information
Ethiopia kale is adaptable to a variety of environments thriving in highlands of up to 2600m with a cool climate and in lowlands with relatively warm and dry conditions. The vegetable crop does well in wide range of soils except in water-logged or saline soils. It grows best in the dry seasons when there are few pests and diseases. The optimum temperature ranges between 15 and 20 degrees Ethiopian kale' small seeds germinate rapidly in moist soils in partial shade or full sun (AVRDC & IPGRI, 2006

Agronomic aspects

Land preparation
Till land to fine tilth due to B. carinata's small seed size. African kale needs to be grown on free-draining soil with good soil fertility – well-decomposed cattle manure should be incorporated into the soil before planting 

Seed sources 
There are various seed sources for Brassica carinata, including commercial seed suppliers, agricultural research institutions, farmer-saved seeds, and seed exchanges. Commercial seed suppliers offer high-quality genetically pure seeds tested for germination rates and essential traits. Agricultural research institutions offer seed for a nominal fee, and farmer-saved seed is a cost-effective option but may lead to genetic drift. Seed exchanges provide diverse genetic material, but ensuring the seed's quality and viability is essential.

Planting 
It is advisable to plant on raised beds to reduce the incidences of damping off disease on the vegetable (AVRDC &IPGRI, 2006). Propagation is generally by seeds and rarely through cuttings. Planting is by direct seeding. It may be broadcasting or in rows – 15cm apart. Broadcasting is not encouraged as it results in uneven plant densities and makes it harder to carry out weeding, fertilizer, insecticide application, and harvesting. It is also more wasteful of seed and manure. Farmers may cover the seedbeds with grass to keep the surface moist and dark. When the cotyledons have spread after germination, this mulch is removed or placed next to the plantlets. Seedlings can be transplanted at the 4-leaf stage, about 5 weeks after germination. Depending on the variety, the field spacing is about 35-40 cm within and 50-60 cm between rows. Seedlings are planted with a spacing of about 75x50 cm for varieties with large leaves, as found in West Africa and Tanzania, and 50x50 cm for the small-leaved varieties in Zambia and Zimbabwe. When grown as an oil crop, seeds are sown directly in lines or broadcast when a short-duration leaf crop is aimed for.

Crop management
Ethiopian kale responds well to manure, and where possible, well-decomposed cattle manure should be incorporated into the soil before planting. Organic matter not only adds nutrients to the soil but also improves the structure of the soil, increasing its water-holding capacity. Manure may be applied at a rate of about ½ - 1kg/m². 
A recommended management is to cut the stems at 15 to 20cm height to encourage the proliferation of more and larger leaves. Frequent irrigation is needed for a good leaf yield. When the rains have stopped and irrigation is unavailable, plants will start to flower and produce seeds. When the crop is sown at the onset of the rains, attack by pests and diseases will be severe. To avoid such attacks, it is recommended that the crop be sown 5-6 weeks before rains are expected so that the crop can be transplanted at the onset of the rains.

Harvest, post-harvest practices and markets

a.    Harvesting 
The first harvest is done while thinning the seedlings from seeds broadcast at high density 6 weeks after sowing. The whole plant is uprooted, especially when the land is needed for another crop. The plants should be about 20cm in height, and thinning should be done to leave a spacing of about 35cm between plants. For a conventional crop, the first harvest takes place about 5 weeks after transplanting. Leaf harvesting is best done once in 2 weeks with 50% defoliation.

b.    Post-Harvest 
Ethiopia kale leaves are rather perishable – they wilt or become yellow if left on the shelf for more than a day. It is, therefore, advisable to only harvest small quantities at a time. To keep them for a long, leaves are kept moist inside a bag left in the shade or in a cool and dry place. When B. carinata is a whole plant with roots, place the roots in water so they can be kept for a few days. Traditionally, the leaves are dried in the shade for consumption in the dry season. Blanching can also be used to preserve the vegetables. Blanching is done by immersing the vegetable leaves in hot water at a certain temperature for a given period or steaming (Cookbook for traditional vegetables).

Seed Production
To produce a crop for seeds, plants must be selected early and left for late flowering. Large leaves, desirable consumption characteristics, good performance, and disease free are all characteristics to look out for. Such a selection is likely to lead to a significant increase in yields. Seedpods should be protected from birds, which split them open to eat the seeds. Pods should be harvested when fully dry, just before they open naturally, and shatter their seeds. The heads should be plucked off and dried on a large sheet in the shade, not in direct sunshine, as this could result in cooked seeds that will not germinate. Drying completely will usually take 3-5 days. Pods are crushed by hand or hit with a stick to release the seeds, then winnowed to clean them. Seeds should be stored in a clean, sealed container or polythene bag. 

Value addition and Market

Brassica carinata is a versatile crop that has attracted attention for its potential as a source of vegetable oil and biofuel. Additionally, the leaves of the plant are a nutritious vegetable, rich in vitamins and minerals and are grown commercially in various countries. In addition to Ethiopia, B. carinata is also grown as a commercial crop in other African countries, including Tanzania, Uganda, Kenya, Malawi, and Zambia. 
B. carinata is a highly desirable crop due to its agronomic superiority and ability to withstand frost compared to other oilseed crops and mustards. Additionally, it boasts a high oil content, large seed size, and lower rates of lodging and shattering in comparison to other species within the Brassica family. These favorable characteristics contribute to its overall marketability and potential for success in the agricultural industry.

Nutritional value and recipes

Brassica carinata is a nutrient dense leafy vegetable rich in vitamins, minerals, and phytochemicals. It is an excellent source of antioxidants, dietary fiber, and protein, and it has been shown to have numerous health benefits.
Ethiopian kale is also a good source of protein, with a protein content of around 25-30% (Mnzava and Schippers, 2007). This makes it an excellent choice for vegetarians and vegans looking for plant-based protein sources. B. carinata is also a good source of vitamins, including vitamin A, thiamin, riboflavin, niacin, and folate. Vitamin A is essential for maintaining healthy vision, skin, and immune function. Thiamin, riboflavin, and niacin are important for energy production and maintaining a healthy nervous system, while folate is necessary for cell growth and development. Furthermore, Brassica carinata has a low glycemic index, which means that it can help regulate blood sugar levels and may be beneficial for people with diabetes.

Table 1: Approximate composition and level of nutrients in raw and cooked Ethiopian kale (Brassica carinata)

Source (Nutrient data): FAO/Government of Kenya. 2018. Kenya Food Composition Tables. Nairobi, 254 pp. http://www.fao.org/3/I9120EN/i9120en.pdf
$ Draining the water several times leaches away water soluble nutrients significantly.
a Lewis, J. 2019. Codex nutrient reference values. Rome. FAO and WHO
b NHS (refers to saturated fat)
c https://www.hsph.harvard.edu/nutritionsource/water/
d British Heart Foundation
e FDA
f NIH
g Mayo Clinic

Complimentary recipes 
a.    Fried kanzira and leaf amaranth (terere) in fresh milk 
Kenyan dish
Ingredients
•    90 g of kanzira (B. carinata)
•    100 g amaranth
•    ½ to 1 cup of water
•    1 tablespoonful of cooking fat
•    1 small onion (60 g when)
•    1 medium-sized tomato (40 g when)
•    ¼ cup of fresh milk
•    Salt to taste (1 pinch)

Preparation
•    Remove stalks of the kale
•    Wash the vegetables separately, and drain and chop the Kanzira only. You may also chop the amaranth
•    Heat the water, add salt, then add the vegetable mixture (blanching). Blanch for 3 minutes. (Blanching is done to retain colour and nutrients). Remove immediately and dip in cold water, then chop
•    In a separate saucepan, heat the fat, add the chopped onion and fry it until it turns golden brown. Ensure onions do not burn
•    Add the chopped tomato and fry them until tender
•    Add the vegetables and stir-fry for five minutes
•    Add salt to taste
•    Vegetables ready to serve

Variation
½ cup Fresh milk or ¼ cream can be added after frying. Cook briefly after adding milk. It is usually better to add tomatoes to vegetables and avoid cooking tomatoes to retain more heat-sensitive Vitamins.
Remarks 
Although this mixture is bitter in taste, all age groups relish it. These vegetables are soft, and their cooking duration is short. This combination is more palatable when fried rather than boiled.

Source; Cookbook for traditional vegetables (IPGRI, 2006). 

b.    Figiri

Ingredients
•    2 handfuls (150 g) Ethiopian mustard leaves
•    One 50 g onion
•    2 (60 g) tomatoes
•    4 tablespoonfuls of cooking oil
•    3 tablespoonful groundnut flour
•    ½ cup fresh milk
•    Salt to taste
•    1 cup of water

Preparation
•    Select the tender leaves of Ethiopian mustard 
•    Wash in clean running water to remove soil and insects
•    Cut the midrib and shred the mustard finely
•    Wash, peel, and chop the tomatoes
•    Clean, wash and chop the onion
•    Fry the onion lightly, add tomatoes, stir and cook till soft
•    Add shredded mustard and stir till well mixed. Simmer while covering the pan for 2 minutes
•    Mix groundnut flour with milk, add into the vegetables and stir for 2 minutes
•    Season to taste and serve as a relish

Variation
•    Use coconut milk, water or cream instead of milk
•    Use peanut butter instead of groundnuts
•    Use meat instead of groundnuts
•    Can add carrots to the recipe

Remark
The vegetable cooks fast so do not overcook it.
 Source; Cookbook for traditional vegetables (IPGRI, 2006).
 

Introduction

Gnetum africanum, commonly known as African joint fir or eru, is a plant species that belongs to the family Gnetaceae and the genus Gnetum. It is one of the several species within the genus Gnetum. The genus comprises approximately 35 species of small trees, shrubs, or most often lianas, found in tropical South and Central America (about 7 species), Africa (2 species), and Asia (about 25 species). They look much like dicotyledonous flowering plants (having opposite leaves with a net venation and cherry-like seeds), although they are gymnosperms. The 2 African species G. africanum and G. buchholzianum, are very similar and have been classified in section Gnetum. They are found in humid tropical forests ranging from Nigeria to Cameroon, the Central African Republic, Gabon, the Democratic Republic of the Congo, and Angola. The two species are quite similar and can only be distinguished by the shape of the leaf and the characteristics of the reproductive structures. In its cultivation zones, Gnetum leaves form a very popular and highly valued vegetable; they are often picked from the wild and sold at local markets, where they are frequently a significant commodity. The plant is highly regarded for its nutritional value, as it is rich in essential nutrients such as vitamins, minerals, and proteins. The leaves of Gnetum africanum are commonly used in traditional African dishes, including soups, stews, and sauces. The plant is highly regarded for its nutritional value, as it is rich in essential nutrients such as vitamins, minerals, and proteins.
In addition to its culinary applications, Gnetum africanum also possesses medicinal properties. It has been traditionally used in African herbal medicine for various purposes, In Nigeria, eru is used for treatment of piles and high blood pressure and also as medicine against enlarged spleen, sore throat and as a purgative. In the Central African Republic, the leaves are eaten to treat nausea and as an antidote to arrow poison made from Periploca nigrescens Afzel. In Cameroon the leaves are chewed to mitigate the effects of drunkenness and they are taken as an enema against constipation and to ease childbirth. They are also used to treat boils and fungal infections on the fingers. The supple stem is sometimes used as rope. Gnetum africanum often commands lower market prices than G. Buchholzianum because of its thinner and paler leaves. Additionally, the leaves are exported to ethnic marketplaces throughout the world. Current harvesting methods are unsustainable, so research is being conducted on economically producing the plant. (Schippers & Besong,, 2004, Mialoundama, 1993).

Species accounts

Both African Gnetum species (Gnetum africanum and Gnetum buchholzianum are dioecious (with plants being either male or female) lianas with two different types of stems. The orthotropic (vertical) ones have small, scale-like leaves and rapidly grow vertically, reaching main branches of a tree where they produce stems with fully developed leaves. The stem continues climbing until it reaches the canopy where it branches into several leafy stems. Female plants often show more vigorous growth with stronger stems than male plants. Eru continues to grow during the dry season and new shoots may develop where the stem has been cut or where side shoots have been removed. Under wild conditions, both species grow and form underground tubers or roots that store plant food reserves. These can remain alive for many years when the vegetation and the Gnetum vines above ground are cleared and the soil surface is laid bare. The distinctly coloured drupe-like seeds are probably dispersed by birds and other animals.

G. africanum leaves are relatively thin, light to pale green, and ovate to oblong in shape. The male catkins are of equal width from the base to their tip. G. buchholzianum leaves are elliptic to oblong in shape, thick and dark green. It produces catkins with a diameter decreasing from the base to the top internode (Schippers, 2004). The dry matter content of fresh Eru leaves is much higher than for other dark or medium green leafy vegetables. This gives a feeling of firmness during preparation, leading some customers to view eru as a meat replacement. Gnetum africanum is threatened with disappearance because of intensive gathering and cultural activities which are destroying the forests that support the plants. Possible adoption into farm systems is a step on the right way to conserving this plant (Orwa et al., 2009, Schippers, 2004).
Ecological requirements
Eru can be found in the rain forest from sea level up to about 1200 m altitude and prefers an annual rainfall of about 3000mm. 
Gnetum africanum and Gnetum buchholzianum thrive in a wide range of habitats, including farm fallows or abandoned farmland, secondary forests, and closed forest. The vines of both Gnetum species climb supporting big and small trees, dead trees, saplings, shrubs, other climbing vines such as rattan palms, and a host of other plant materials in the complex tropical humid forest, where they grow luxuriantly and produce significant quantities of leaf biomass. It is usually found on middle and under-storey trees together with other climbers and frequently forms thickets. It can also be found in riverine forest areas that are otherwise too dry for the species. Gnetum africanum is mainly found at the periphery of primary and secondary forests. Gnetum buchholzianum is primarily found in the forest, especially near openings created by fallen trees (Asaha, 2000, Mialoundama 1993, Shiembo, 1996, Shiembo, 1999, Schippers, 2000).
Agronomic aspects 
Seed germination is slow and irregular; germination periods of 1 year or more are pretty normal. Even so, the germination percentage is very low in a nursery. It is assumed that seeds need pretreatment, such as passing through the intestines of a bird, fruit bat, squirrel, or other animals, before they germinate. Seed is typically found only in the tree canopy. Seed collection is thus far from easy, a reason why eru is hardly cultivated.
The cheapest propagation method available is rooted cutting. Fresh stem cutting is taken, for which a stem with a single pair of leaves is adequate. These cuttings are placed in well-decomposed sawdust as a rooting medium, and care is taken to keep the leaves moist. A mist system is ideal for this purpose, although not essential, and other means of keeping the leaves wet with a fine spray if water can also be used.
Evapotranspiration of the new cuttings should be minimized and it is recommended that the plant bed be covered with fine gauze, nylon net, or a loosely woven piece of cloth. Once rooting has taken place, which may take about a month, the new plantlets should be transferred to a proper growing medium with forest soil. Polythene sleeves filled with soil can be used for this purpose. Once side shoots have developed from the nodes, plants should be given more space to create an adequate flow of air 
After about 6 weeks, the rooted cuttings are transferred to polythene sleeves, bamboo pots, or other containers, where they remain for a further 2-3 months. The soil mixture for these containers consists of 25% sand and some compost, supplemented with forest soil. Field planting occurs at the beginning of the rainy season, preferably next to a young tree or shrub.

Management
Eru is mainly collected from wild stands; farmers often retain it when clearing fields. If cultivated, farmers need to provide support, e.g., by using commercial plantations of rubber trees, oil palm, and other crops. The use of fences was only found to be successful when there is enough shade, and it is generally too expensive. Fully exposed plants do not grow well; their leaves are thin and pale green. In experiments, nutrients, especially nitrogen, have shown a positive effect on growth and rate of leaf development.

Harvest, post-harvest practices

The current method of harvesting, especially for export trade, is by either uprooting whole plants or pulling the stems from the trees. This leads to large-scale destruction of natural stands. Occasionally, trees have to be cut to reach leafy stems in the canopy. This is mainly done during the dry season when the forest is more accessible and where there is little work on the farm. Controlled harvesting in which only side shoots or parts of stems are collected is clearly better than destructive harvesting. After such harvesting, new shoots may develop where a stem has been cut or where side shoots have been removed. Preliminary observation indicates that 3-4 harvests per year are possible, whilst still allowing substantial regrowth. More frequent harvesting will result in thin leaves that are considered inferior. 
The first harvest may take place 6-9 months after planting and the total lifespan of eru is estimated at over 10 years.

Post-harvest practices
Leaflet stems of eru remain fresh for at least a week. Branches collected from the forest are brought to collecting points from where they are sold in the local markets or exported. For this trade, whole leafy stems are packed in large bales. Selection takes place on the size and texture of the leaves, which is mainly dependent on the species. Gnetum buchholzianum is more popular with consumers and expensive because its leaves are generally thicker than those of Gnetum africanum. The fresh leaves are somewhat leathery and are thus tough to eat whole. The leaves are therefore shredded into strips about 2 mm wide. This product can be prepared directly or dried for later use after reconstitution by soaking in water. This shredding process is done by placing several leaves on top of each other and cutting them with a sharp knife. It is a tedious job that is often done before export, mainly to black communities of Nigerian and Cameroonian origin in the U.S. and the U.K. (Schippers and Feeday, 1998).
Gnetum is often eaten as part of a mixture in a groundnut-based stew. It often replaces meat because of its high protein content and is thus much appreciated. To soften the otherwise tough product, people mix Eru with waterleaf, Talinum fruticosum, and these two vegetables are always eaten together.

Value addition, and market value 
Preservation of Gnetum
Chopped well-dried leaves are packaged in containers e.g. in polythene bags and stored in room temperature. They may keep well for about 1 year. The stored leaves are soaked in hot water prior to cooking.
In trade, consignments of Gnetum africanum and Gnetum buchholzianum are often mixed. Traders will pay more for the thick dark green leaves of the latter, but much variation is also caused by growing conditions. Most eru is consumed locally, but intensive trade has developed from Cameroon and more recently also from Gabon and the Central African Republic to meet the large demand in Nigeria. Most eru from Cameroon, Gabon and the Central African Republic is transported to Idenau, a coastal village in Cameroon, and from there by boat to Nigeria. Estimates for the annual export of eru leaves (both species) to Nigeria range between 2500 t and 4000 t. Another major marketing centre is the Koilo Region in Congo. Other marketing centres in Cameroon are Campo near Kribi for export to Gabon and the Mfoundi market in Yaoundé. Dried shredded leaves are exported, mainly from Nigeria to the United States and to a lesser extent from other countries to France and the United Kingdom (Schippers, R.R. & Besong, M.T., 2004).

Nutritional value and complimentary recipes 

Gnetum africanum is rich in fiber (28–37%) and protein (13–18%). The plant is high in carbohydrates -38–44% dry matter. Other values based on 100 g dry weight of leaves indicate: carbohydrates 70 g, of which 40 g is cellulose, protein 16.5 g, lipids 6 g and ash 7 g. The caloric value for G. africanum leaves therefore is much higher than in most vegetables, 248 to 307 kcal/100 g (Ali et al. 2011). The high protein and fat content of eru leaves explain why it is often used as a substitute for meat. The protein of Eru has all eight essential amino acids (isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine). This nutrient composition of Gnetum varies depending on the variety. The nutritional value of Gnetum buchholzianum is often higher than that of Gnetum africanum.

Proximate composition and level of nutrients in Gnetum leaves prepared in different ways

1Data in %. Source: AVRDC & IPGRI, 2006
2 Data in ppm. Source AVRDC & IPGRI, 2006. To convert to %, divide by 10000.
3Chemical composition of G. africanum (% of dry matter), Ali et al. 2011 (Ali, Fadi & Assanta, Mafu & Robert, Carole. (2011). Gnetum africanum: A Wild Food Plant from the African Forest with Many Nutritional and Medicinal Properties. Journal of medicinal food. 14. 1289-97. 10.1089/jmf.2010.0327.)
 4Chemical composition of G. africanum in %. Source: Ali et al. 2011.
RE=retinol equivalents. 
RAE =Retinol activity equivalents. A RAE is defined as 1μg all-trans-retinol, 12μg beta-carotene, or 24μg α-carotene or β-cryptoxanthin.
a Lewis, J. 2019. Codex nutrient reference values. Rome. FAO and WHO
b NHS (refers to saturated fat)
c https://www.hsph.harvard.edu/nutritionsource/water/
d British Heart Foundation
e FDA
f NIH
g Mayo Clinic

Complimentary recipes

1. Fumbwa (Kikongo, Lingala)
(DRC recipe of Gnetum)
Ingredients
1 teaspoonful salt
1 green pepper
4 tablespoonfuls of palm oil
8 tomatoes 
1 magii cube (seasoning)
10 teaspoonfuls peanut butter
2 onions, medium size 
300 g smoked fish
4 cups water

Preparation
Wash leaves and cut them into small pieces
Bring water to boil and then soak the leaves
Wash the leaves 3 times in the hot water
Heat palm oil and add all ingredients at once i.e. tomatoes, peanut butter, flavoring cube and smoked fish
Mix all the ingredients, add salt to taste and then add water
Cook in low fire till the vegetable is soft. This may take up to 2 hours
Serve with manioc or maize fufu. One may also eat with chikwangue

Remarks 
The Bakongo people of west DRC like this vegetable. They have however influenced other communities living in the capital, Kinshasa. Note also that, this preparation requires a lot of peanut butter and cooking because it is coarse.

2. Gnetum africanum with palm oil and peanut. 
Ingredients
•    500 g (or more) of Gnetum africanum, or substitute any other greens: Cassava leaves, collards, kale, turnip greens or similar; or spinach; cleaned, stems removed; and shredded, finely cut, or pounded in a mortar with a pestle 
•    one cup peanuts (or peanut butter) 
•    one or two ripe tomatoes, peeled and chopped (or canned tomato paste, or canned tomato) 
•    one leek (or one onion), finely chopped 
•    one piece of dried, salted, or smoked fish (the size of your hand), bones and skin removed, cleaned, soaked in water, and rinsed 
•    one cup red palm oil

Preparation procedure
•    Place the greens in a large pot. Add enough water to partially cover. Bring to a boil. Reduce heat, (do not cover), and simmer until greens begin to become tender. (Cooking time varies considerably depending on type of greens used.) Add water if pot becomes dry.
•    Grind, chop, or pound peanuts into a fine paste. (Or you can start with natural, sugar-free peanut butter.)
•    When greens are mostly tender and liquid is reduced, add tomatoes (or tomato paste), leek (or onion), and dried fish. Continue to simmer, on low heat, stirring occasionally. Simmer until everything is tender and ready to eat. 
•    Remove a cup of the pot liquid and combine it with the peanut paste in a bowl. Stir to obtain a smooth sauce. Stir the peanut sauce into the greens, and reduce heat to as low as possible. Top with red palm oil and simmer for a few more minutes. 
•    Serve with boiled yams or sweet potatoes and/or cassava tuber, banana leaf or rice. 
Source: http://www.congocookbook.com/c0219.html

Genetic resources
Eru is hardly cultivated at all at present. There is still massive exploitation of the remaining natural stands, which have almost disappeared in Nigeria and are becoming scarce in Cameroon, Gabon, and the Central African Republic. There is an urgent need to collect and preserve the diversity found within the two African Gnetum species, preferably throughout their natural range (AVRDC & IPGRI, 2006.) 

Prospects
Alternatives to destructive harvesting of eru should be found. Once the new methods of propagation and cultivation have been adopted, there will be scope for the development of eru as a new crop, for which there is already high demand and an attractive price could be paid. The diversity found between accessions is considerable, offering scope for improving quality and productivity (AVRDC & IPGRI, 2006).