The pigeon pea has been grown by humans for more than 3,000 years and in some parts of the world it is an important source of protein. In the U.S. it has grown a bit out of favor among consumers and gardeners but it still has its uses, both as food as well as green manure or other cover crop uses.
Pigeon pea is scientifically known as Cajanus cajan and is, as the common name suggests, in the pea family or Fabaceae. It goes by various other names around the world, the more common English names being tropical green pea, no-eye pea, and Congo pea. In India, the split form of the pea is call toor dal and is a popular component of many recipes, most specifically lentil soup (dal).
Pigeon pea was first cultivated and is most likely native to southern India. From there it travelled to East and West Africa and from there to Europe and the Americas (via the slave trade). Now it is grown throughout the tropical regions of the world and has been incorporated into many traditional dishes.
In Hawaii, the pigeon pea has sometimes escaped from cultivation and has become sparingly naturalized. Although it survives on its own in Hawaii, it is not a particularly invasive species and tends to be found in already altered ecosystems. It has been around long enough to have a Hawaiian name (though it is not a Hawaiian native) and is known as pī nūnū or pī Pokoliko. “Pī nūnū” is a literal translation of “pigeon pea” and “pī Pokoliko” is a literal translation of “Puerto Rican pea.”
Pigeon peas and rice is a traditional Puerto Rican dish and most likely the origin of the Hawaiian name for the plant. It is interesting to note, though, that the pigeon pea has been in Hawaii since at least 1864, 36 years before the first Puerto Ricans were brought to Hawaii to work on the sugar plantations. Who actually brought the pigeon pea to Hawaii is not documented.
According to the Manual of the Flowering Plants of Hawai`i (published in 1990 by University of Hawaii Press and Bishop Museum Press) the pigeon pea may be found “apparently naturalized in open disturbed areas such as roadsides, pastures, and cane fields” from about 80 to 2000 foot elevations. It can be found on all the main islands in Hawaii.
Pigeon peas come in a variety of forms. There are annual varieties and short-lived perennial types. In Hawaii we have the perennial types but there are probably seed companies can that can sell you the annual varieties. The perennial ones can be short shrubs averaging 3 or 4 feet tall or taller shrubs, up to about 12 feet tall, when flowering.
Pigeon peas are easy to grow from seeds, though it may take a little while for the plants to take off. The seed germinate in one or two weeks from planting and may stay only a foot or two tall with one main stem for the first month or two. Once they get themselves established, though, they start growing quickly and within three to five months they are full and bushy. I tend to trim mine to keep them under control and use the trimmings in my compost or as nitrogen-rich mulch. This may slow down the flowering process but the clippings are well worth the wait and the bushier plants end up having more flowers – and seeds.
As a legume the pigeon pea is a nitrogen fixing plant. That means they have associated bacteria that take nitrogen from the air (N2) and change its form into one that is available for plants (NH4). Most parts of the plants are fairly high in nitrogen and as they decompose, add nitrogen to the soil (or compost) making it available to other plants. Nitrogen is also left in the soil by the decomposing roots, enriching the soils for other plants. This is what makes pigeon peas one of the recommended “green manures” used to enrich soils.
Even if it isn’t used as a green manure (worked into the soil before allowing to flower) but is grown as a crop, it is good to follow a pigeon pea crop with plants that need richer soils, such as corn or squashes. The bushy types can be trimmed and the main stems left behind to allow vine crops to grow on them. Or the whole plant can be trimmed to the ground (not disturbing the soil too much to allow the roots to decompose) and grain-type crops or greens can be grown, to use the released nitrogen.
As a legume, the pigeon pea has a typical pea-like flower. Those grown in Hawaii have yellow flowers with darker veins. They are attractive to honeybees, leafcutter bees and carpenter bees, as well as other pollinators, and relatively quickly followed by green seedpods. The seedpods are 1½ to 2½ inches long and about ¼-inch wide with three to nine seeds in them. The seeds are a little less than ¼- to a little more than ⅓-inch in diameter and slightly flattened balls. The range in color from light tan to nearly black.
The seeds can be eaten green or dried. In some parts of the world the pods themselves are eaten. Boiled green, nearly-mature seeds pods can be eaten like edamame or the green seeds removed and quickly parboiled and eaten like green peas or added to soups and stews. The dried seeds can be used any way dried beans are used. Pigeon peas and rice is particularly flavor-full and provide a complete protein for those trying to reduce or eliminate meat products from their diet. Pigeon peas are an important part of a vegetarian diet in parts of India.
So even though most Western gardeners and farmers have relegated the pigeon pea to green manure or animal food status, give this old staple a try. It is easy to grow, leaves garden soil in better shape than before it was planted, and adds some flavor to many dishes.