The bush onion (Cyperus bulbosus) is an annual sedge with grassy leaves and chocolate brown seed heads. The roots produce many small bulbs up to 10 cm underground.
This has been one of the most important food plants in the bush area in Central Australia for tens of thousands of years, especially in times of drought. It is a totemic plant, featuring in many indigenous songs and in indigenous mythology of each of the seven indigenous language groups within Central Australia. Important increase ceremonies are held regularly. Bush onions are usually and traditionally eaten by Indigenous people.
They were once quite commons, but changes in land and fire management are pushing the bush onion closer to extinction. For example, it is encouraged by fire, but only grows after rain. So a change in management, which allows wild fires independent of any knowledge of forthcoming rain events, leads to the plant’s destruction. The greatest threat to the bush onion comes from the introduced buffel grass (Cenchrus ciliaris) which outcompetes and smothers the onion grass. The cattle industry in Central Australia strongly supports the continuance of buffel grass even though it is a poor substitute for indigenous grasses and other indigenous flora.
In comparison to other parts of the world, Central Australia does not appear to support a great number of plants with edible underground roots. As they are in high demand during drought periods, these plants can be under severe stress. Predation from termites can also severely reduce the crop.
The bush onion once cooked, by shaking it with hot coals in a dish, has a pleasant nutty taste. This was once an important food source, especially in times of drought. The white inner flesh, which is covered by a thin papery skin, can be eaten raw or cooked in hot ashes.
The nutritional value of these starchy foods is limited, however the high water content of at least one of these tubers was important to some Indigenous people. During cooler months this source of water allowed them to live in drier areas for long periods.