Black Bean Beauty

Skyrail Nature Diary: November 2005


Renowned for its stunning red and yellow flowering displays, many people are unaware of the hidden qualities of the Black Bean (Castanospermum australe).

Also known as the Moreton Bay Chestnut, the Black Bean belongs to the Fabaceae family, one of the largest families of flowering plants. This plant, however, leads a lonely existence as the sole member of the Castanospermum genus; its nearest relative is located in South America.

Black Bean trees are found throughout rainforests from NSW to the tip of Cape York Peninsula, and have also been recorded in New Caledonia and Vanuatu. Black Beans prefer rich, moist soil, but it is a hardy plant that can tolerate a variety of conditions including frost, heavy shade and full exposure to the sun.

The Black Bean’s name comes from the large seed pods that appear on the tree between March and May, which split open to reveal three or more large, bean-like seeds. The seeds and leaves are toxic to livestock, and subsequently many Black Bean trees have been cleared from grazing areas.

Between September and December, the Black Bean bursts forth with spectacular flower arrangements any florist would be proud of! It is these flowers, along with a crown of up to 8 metres wide, that make it a popular shade tree in parks and gardens. The Black Bean is a hive of activity when flowering, with many native parrots, bats and butterflies flocking to its red and yellow flowers to sample the nectar.

The Black Bean’s outward beauty does, however, overshadow an impressive resume. The tree yields a beautiful hardwood ranging from dark brown to black in colour, making this a much-valued timber for turnery, flooring and furniture. In fact, a chair made from Black Bean timber takes pride of place in the British House of Commons as the Speaker’s Chair, a gift from the Australian Government.

Not content with a position in world politics, the Black Bean has also made a foray into the world of pharmaceuticals and medicine. Scientists in the 1980s discovered that a compound found in the tree, later named castanospermine, possessed the potential to kill the HIV virus.

Clinical trials were held to test this theory, but due to uncertainty regarding side-effects (it is toxic, remember!) it was eventually dropped for a different compound. However, castanospermine is still used as a base for developing other compounds, and has been found to have anti-inflammatory and anti-cancer properties.

The Aborigines found the Black Bean’s seeds a reliable, albeit cumbersome, source of protein, fat and fibre. After cooking in a traditional earth oven, the seeds were sliced and soaked in running water for up to three days; this would wash the toxins out, after which the seeds were ready to eat. Seeds were also crushed and sprinkled into pools of water to attract and catch freshwater shrimp.

Australia’s Tropical Rainforests are home to more than 3,000 different plant species from 210 families. Skyrail Rainforest Cableway provides guests with the perfect opportunity to view rainforest flora from above the canopy, before alighting at rainforest mid-stations to learn more from the forest floor.