Castanospermum australe, often called Black Bean or Moreton Bay Chestnut is a rather nice tree native to the coastal rainforests and beaches from Lismore in northern New South Wales to the Iron Range on the Cape York Peninsular in northern Queensland in Australia. Although native to north-eastern Australia, these trees are hardy to many conditions within the country, but will be shorter-in Melbourne it will only reach a height of 8 metres (rather than the 40m at maturity further north). The binomial name means the following:

• Castanospermum-comes from two words, ‘castanea’ which is Latin for chestnut and ‘spermum’ is Greek for seeded.
• Australe-Latin for southern, in reference here to the southern hemisphere.

In its native habitat, the Moreton Bay Chestnut grows in soil that is moist but well-drained and fertile located on hillsides and riverbanks. the tree prefers full sun but tolerates shade and light frost.

The leaves are pinnate, 30-6 cm long with individual leaflets being 7-20 am long and 3 cm wide. The margins are entire, the upper leaf surface is glossy and glabrous while the lower surface is paler and dull.

The flowers appear in spring in racemes up to 15 cm long. They are orange to red in colour, contrasting nicely when seen as they are partially hidden by the leaves. Flowers are followed by pods that contain between 1-5 seeds that are quite large in comparison to other seeds.

When grown in cultivation, these trees have a rounded habit, reaching up to 20 metres in height and 8 metres in spread. They are useful shade trees in gardens, parks and anywhere else with space for a good sized tree.

Other uses of the tree are as a plant to help stabilise steam and river banks as the root system is extensive (BUT don’t plant one within 10 metres of drains, sewers, building foundations and swimming pools. It is also a good timber tree. It also contains alkaloids that apparently have anti-HIV and anti-cancer properties (but you should always follow doctors advice when unwell, as such compounds have to go through various processes to make them useful in the relevant way-and people far more educated than me do this sort of valuable work).

It is also worth noting that the seeds and leaves are toxic to livestock, so don’t plant in a situation where livestock could then eat them.

• All photos are my own
• https://www.anbg.gov.au/gnp/intern-2002/castanospermum-australe.html. Accessed 14/12/23
• https://www.plantnetrbgsyd.nsw.gov.au. Accessed 14/12/23