Geography and distribution
Pigeon pea was first domesticated in India where it has been growing for thousands of years. Around 2,000 BC, a second centre of pigeon pea diversity was developed in East Africa and from there, probably as a result of the slave trade, the crop was brought to the Americas. Today pigeon pea is grown throughout tropical and subtropical regions of the world; the largest producer is India, followed by East Africa and Central America.
Pigeon pea (Photo: Forest and Kim Starr)
Overview: Cajanus cajan is an erect shrub up to 4 metres tall, with roots that extend up to 2 metres into the soil. Its main stem is erect, ribbed and the plant has many secondary branches.
Leaves: The leaves are alternate along the stems and are composed of three leaflets (tri-foliolate) and they are positioned alternately along the stem. The petiole (the stalk which connects the leaf to the stem) is 1-8 cm long and grooved above. The leaflets are elliptical (like a stretched circle when flat) to lance-shaped (lanceolate) and are 2.5-13.5 cm long to 1-5.5 cm wide. The leaflets are green above and a silvery grey-green beneath and are covered on their lower surfaces in small yellow glands.
Flowers: The stalked flowers are arranged along an unbranched axis (a raceme). The racemes are axillary (arising from the point between the main stem and a leaf). The flowers are yellow and are papilionaceous, typical of species belonging to the Leguminosae subfamily Papilionoideae, and resemble, for example, the pea (Pisum sativum) flower. Each flower has 10 stamens, 9 of which are fused into a partial tube, with the tenth stamen free. The ovary is positioned above the sepals, petals and stamens. The style is curved.
Fruit: The fruit is a straight or sickle-shaped pod 2-13 cm long x 0.5-1.5 cm wide containing up to 9 seeds. The seeds are 4-9 mm x 3-8 mm and can be white, brown, purplish, black or mottled.
Threats and conservation
Cajanus cajan is not considered to be threatened although wild populations are unknown.
Pigeon pea is cultivated mainly for its edible seeds, which are rich in protein and add a nutty flavour to many food preparations.
- In India, pigeon pea is most commonly used in 'dhal' (soaked dried, hulled, and split seeds) and in many other parts of Asia the seeds are used instead of soya bean to make tempeh or tofu.
- In Africa, the dried seeds are typically used in sauces to accompany staple food preparations such as rice, yam and cassava. The immature seeds and pods of pigeon pea can be eaten fresh as a vegetable in soups and sauces and when ripe, the seeds are often soaked first before frying or boiling them into porridge.
- In Central America pigeon pea seeds are canned and frozen so that they can be stored and eaten when the crop is no longer in season.
Tin of pigeon peas (Photo: Rusty Clark)
Besides being an excellent food source for humans, the seed pods and the leaves of pigeon pea are used to feed livestock and the plants themselves make a useful living fence, windbreaker, shade cover crop and support for vanilla.
Pigeon pea has the ability to fix atmospheric nitrogen through bacteria housed in root nodules, making it a good fertiliser for the soil.
The stems and branches are used for basketry, thatching, fencing and as fuel. It also serves as a host for silkworm and the lac insect.
The leaves of pigeon pea are used in traditional medicine to treat diarrhoea, gonorrhoea, measles, burns, eye infections, earache, sore throat, sore gums, toothache, anaemia, intestinal worms, dizziness and epilepsy. Remedies prepared from the root of the plant are taken to treat cough, stomach problems and syphilis. The roots are chewed to relieve toothache and in Madagascar the leaves are used to clean the teeth.
Crop wild relatives of pigeon pea
The Millennium Seed Bank and the Global Crop Diversity Trust are engaged in a ten-year project, called 'Adapting Agriculture to Climate Change'. The project aims to protect, collect and prepare the wild relatives of 29 key food crops, including pigeon pea, so that they are available to pre-breeders for the development of new varieties that are more resilient to the effects of climate change.
Millennium Seed Bank: Seed storage
The Millennium Seed Bank Partnership aims to save plants worldwide, focusing on those plants which are under threat and those which are of most use in the future. Once seeds have been collected they are dried, packaged and stored at -20°C in Kew’s Millennium Seed Bank vault.
Description of seeds: Average weight of 1,000 seeds = 98.5 g
Number of seed collections stored in the Millennium Seed Bank: One
Seed storage behaviour: Orthodox (the seeds of this plant can be dried to a low moisture content without significantly reducing their viability. This means they are suitable for long-term frozen storage).
Germination testing: Successful
This species at Kew
Pressed and dried specimens of pigeon pea are held in Kew's Herbarium, where they are available to researchers by appointment. Details and images of some of these specimens can be seen online in Kew's Herbarium Catalogue.