Sow Pigeon Peas For Native Bees

A feast for people and bees: trial sowing of pigeon pea, Cajanus cajan, in 2009.

Pigeon peas are a perfect 21st century crop: they cope with warm, dry conditions in the subtropics and tropics. Last spring I decided to grow my own dal. Pigeon pea seed, Cajanus cajan, is listed under this name in seed catalogues  In shops, you buy them as split peas. These protein-rich seed are the main ingredient in dal, and they’re also added to soups and stews.

Pigeon peas are as useful as corn, but they have a smaller ecological footprint. They require far less food, water, pest control and they are easier but slower to grow. They’re a universal food, and India grows 80% of the global harvest.

They’re short-lived shrubs, 2 – 4 metres high. Their first crop is the heaviest, consequently they’re farmed as annuals. Unlike corn, they aren’t too fussy about soil type, as long as it has been well dug and, ideally enriched with either compost, cow or horse manure, or a green manure.

Pigeon pea is a legume, so their roots fix nitrogen. When you buy their seed it should come supplied with a small packet of a compatible strain of nitrogen fixing bacteria. You can buy packet seed supplied with innoculant on line, and you can buy the compatible innoculant separately. By inoculating the soil where you sow or plant pigeon peas you guarantee their roots will fix atmospheric nitrogen. Ploughing their roots back after cropping allows them to release their nitrates and carbon as they decay, feeding and improving the soil.

Indian farmers grow pigeon peas for good reason. Their side shoots make good mulch and they provide forage for livestock. Thicker stems produce firewood suitable for cooking. Plants can tolerate slightly saline soil (or bore water), and they only need trace elements or fertiliser to counteract known deficiencies in the soil. Above all, pigeon pea is drought tolerant: 600 – 800mm of rainfall produces a crop if most of the rain falls during summer.

Market gardeners often interplant rows of plant pigeon pea with crops, like sorghum, or fruit trees, like persimmon. Dried peas can be picked young and eaten green or when brown and fully mature. Some Australian cotton growers plant pigeon pea around cotton fields as a trap crop; pigeon pea leaves are more attractive to caterpillars than cotton. Pigeon peas are Climate Change winners, a 21st century crop for the poor and for farmers on marginal land. In drought in India, farmers turn from growing onions as a cash crop to pigeon peas as a survival crop.

Modern cultivars can be early maturing, cropping 3 – 4 months from sowing, old-fashioned cultivars are late maturing at between 5 – 11 months old. Mine are descended from a late maturing cultivar acquired from the Seed Savers’ Network ten years ago, the type traditionally grown because the seed are about 30% larger than the modern, faster growing cultivars preferred by industrial farmers.

I sow mine in my subtropical garden in October. I sow three seed in a 100mm round tube. Every seed germinates: I thin to retain the strongest seedling and then plant immediately the first roots start appearing in the drainage holes to prevent them becoming root bound. By late March, plants resemble leafy umbrellas four metres tall and that’s when flowering begins.

Peak flowering lasts around six weeks and, curiously, honeybees seem disinterested. Native bees find them irresistible, their visits increasing as flowering peaks. Fascinated, one weekend I observed their group dynamics. The first and last to visit were energetic blue-banded bees, (Amegilla cingulata). Around midday along came teddy bear (Amegilla bombiformis) and carpenter bees (Xylocopa aruana). Carpenter bees are divas; large, colourful, energetic and noisy. After drinking deeply, off they zoom.

But most of the massed action came from fire-tailed resin bees (Megachile mystaceana)and leafcutter bees (Megachile inermis). The leafcutters assertively drove off others, like the blue-banded bees.

Blue-banded bees

Dr Tim Heard, formerly a CSIRO entomologist, a leading Australian native bee expert, and Brisbane-based supplier of stingless bees and beehives, first visited my garden in May 2009. Captivated by busy pollinators on my pigeon peas, Tim identified another bee of the genus Chalicodoma (since reclassified as Megachile), working their flowers.

Tim explained how important the blue-banded bee is to horticulture. These are solitary species, but frequently nest in communities. They’re common, occurring everywhere except the NT and Tasmania. Soft sandstone, mud-brick and old mortar are favoured nesting sites. At night, males congregate on thin-stemmed plants, like grasses, resting and holding on with their mandibles.

Commercial tomato growers, through the Australian Hydroponic and Greenhouse Association, have been lobbying for the introduction of the exotic European bumblebee (Bombus terrestris) to increase yields and profit. Conservationists are already alarmed by the recent appearance of the bumblebee in Tasmania, where they are competing with native bees for pollen and nectar. Bumblebees are inefficient pollinators of natives, but pollinate weeds and exotics.

The Australian Native Bee Research Centre has proven the blue-banded bee is superior to bumblebee pollination of avocado, eggplant and tomato. Blue-banded bees are buzz pollinators, using wing beats to vibrate pollen off for collection. ANBRC techniques for establishing new colonies now offer a viable alternative to the bumblebee.

With six bee species working my pigeon peas, every flower set pods. Branches drooped under their heavy burden. Storms further bent branches earthwards, a reminder to space plants two metres apart, and to be prepared to stake them too.

I was pleased to be able to surprise Tim when I told him my blue-banded bees don’t vanish in winter, as they’re supposed to do. They forage on salvias and bedding begonias, proof that we can never know everything about gardening. (In July 2010, Tim witnessed one feeding on the Salvia discolor in my front garden).

You can discover more about native bees by subscribing to the free email newsletter of the Australian Native Bee Research Centre.

If you want protein-rich pigeon peas by the bucketful, grow them in drought. And plant pigeon peas for food, shade, shelter, forage and bees. Grow them in a school food garden to discover which species of native bee live in the vicinity. Use this food plant as a school science project!

Jerry Coleby-Williams
7th October 2019