Sow Pigeon Peas For Native Bees

Pigeon peas are a 21st century crop. Last spring I decided to grow my own dal. Protein-rich split peas are the main ingredient, also added to soups and stews, and these are dried pigeon pea seed, Cajanus cajan.

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

Indian farmers grow pigeon peas for good reason. They’re short-lived shrubs, 2 – 4 metres high. Their first crop is heavy, so they’re grown as annuals. Unlike maize, they aren’t too fussy about soil type, their roots fix nitrogen, shoots make good mulch and forage for stock. Stems produce firewood for cooking, plants tolerate slightly saline soil, don’t need fertiliser, and they’re drought-tolerant: 600 – 800mm of warm season rainfall produces a crop.

Smallholders often interplant rows of plant pigeon pea with crops, like sorghum, or fruit trees. Dried peas can be eaten green or when brown and fully mature. Pigeon peas are a 21st century crop, especially for poor farmers and marginal land. They’re Climate Change winners.

Cultivars can be early maturing (3 – 4 months) or late maturing (5 – 11 months). I sowed mine in my Brisbane garden in October. Every seed germinated: I thinned heavily. By late March, plants resembled leafy umbrellas four metres tall and the first flowers opened. Mine were a late maturing cultivar, the type traditionally grown. Modern cultivars are early maturing and preferred by industrial farmers.

Flowering lasted six weeks and, curiously, our honeybees seemed disinterested. Native bees found them irresistible, their visits increasing as flowering peaked. 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 sp.) and carpenter bees (Xylocopa aruana). Carpenter bees are divas, large, colourful, energetic and noisy. After drinking deeply, off they zoom.

But most of the 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

Tim Heard, a local CSIRO entomologist and native bee expert, visited my garden in May. Captivated by the pigeon pea scene, he identified another bee of the genus Chalicodoma, 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 them two metres apart, and possibly stake them too.

Tim Heard was surprised 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.

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

Jerry Coleby-Williams
7th October 2008