Common Name: Moreton Bay Chestnut

General Information

Castanospermum australe is a tall, evergreen tree with a very dense crown of abundant, dark-green, glossy foliage[]. It grows up to 40 metres tall with a bole up to 120cm in diameter[].
The seeds are a traditional staple food of the Australian Aborigines, and are also harvested from the wild by other people. The tree is most attractive at flowering time with sprays of orange-red flowers and also when bearing its large pendant, cylindrical, bean-like fruits[]. It is therefore often planted as an ornamental in warm temperate to tropical areas[].

Known Hazards

The immature seed is poisonous, though mature seeds are harmless[, ]. Another report says that the raw seed is poisonous and needs treatment to render it edible[]. The seed needs to be cut in slices and washed for several days prior to consumption, otherwise it can cause severe gastrointestinal disturbance[].

Botanical References

Range

Australia - northern New South Wales, Queensland; southwestern Pacific - New Caledonia, Vanuatu

Habitat

Subtropical and tropical gallery-type rainforests and on the banks of creeks[, ], usually in good rich moist soils[].

Properties

Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Evergreen Tree
Height	18.00 m
Growth Rate	Slow
Pollinators	Birds
Cultivation Status	Ornamental, Wild

Cultivation Details

Castanospermum australe is a tree of moist, lowland tropical and subtropical climates, it grows best at an elevation between 50 - 750 metres[, ]. It prefers a mean annual rainfall in the range 1,600 - 3,200mm, but tolerates 1,000 - 3,800mm[]. It grows best in areas where annual daytime temperatures are within the range 20 - 32°c, but can tolerate 10 - 41°c[]. There are conflicting reports on hardiness - one report says that the plant only tolerates short-lived light frosts with occasional temperatures down to about -5°c in its native range and is less tolerant than this when cultivated, whilst another report says that it can succeed in areas that are cooler than its natural range[]. It is said to be able to grow outdoors in south Cornwall (hardiness zone 9)[].
Requires a very well-drained[] but moist high-grade soil and a very sunny position when grown in areas cooler than its natural climate[, ].
The crushed leaves smell like cucumbers[].
Flowers are produced on the old wood[]. The flowers are rich in nectar and are pollinated by parrots in the wild[].
This species has a symbiotic relationship with certain soil bacteria, these bacteria form nodules on the roots and fix atmospheric nitrogen. Some of this nitrogen is utilized by the growing plant but some can also be used by other plants growing nearby[].

Edible Uses

Seed - cooked[, , , ]. The fresh raw seed contains high levels of saponins[] and can be harmful[, ]. The cooked seed tastes like a sweet chestnut[]. It probably requires considerable leeching before it is safe to eat[]. The Australian aborigines finely sliced the seeds and soaked them in running water for 10 days before roasting them and grinding them into a powder[]. This powder could be stored for later use[]. The seeds are about 3 - 4.5cm wide and are carried in pods 10 - 25cm long and containing 3 - 5 seeds[, ].

Medicinal

The seed yields compounds called castanospermine that are under investigation as HIV inhibitors and might be useful in the treatment of AIDS[, , , ].
Parts of the tree contain chemicals which, after careful extraction, have been shown to have anti-cancer, anti-inflammatory, and anti-HIV properties[].

The seedpods are astringent[].

Used to treat post-prandial hyperglycaemia in diabetic patients[].

Agroforestry Uses:

The extensive root system is used to protect riverbanks and catchment areas in Australia[].

Other Uses

The seeds have a high saponin content[]. Although the report does not elaborate, the saponins could probably be used as a soap substitute[].

The seeds contain toxic saponins which are reportedly toxic to a serious pest of stored grain[].

The heartwood is dark-brown to almost black; the sapwood varies from white to yellow. The grain is straight, though sometimes interlocked, the texture is slightly greasy. The wood is hard, heavy, durable, resists decay. It polishes well and has a high resistance to the passage of electric current. It is used in construction, cabinet making, carving etc[, , , ]. One of the most valuable woods in Australia, the sliced veneers can be good substitute for teak[]. The wood has a density of 700 kg /cu m[].
The wood can be used as a fuel[].

Propagation

Seed - we have no details on this species but would recommend sowing it in a greenhouse as soon as it is ripe (if you can get hold of ripe seed!). Pre-soak stored seed for 24 hours in warm water and sow in a greenhouse. Prick out the seedlings into individual deep pots as soon as they are large enough to handle. Grow them on for at least the first winter in a greenhouse before planting out in the summer. Give the plants some protection from winter cold for their first year or two outdoors.