Beans, Plums & Fruits of the Forest

Skyrail Nature Diary: January 2010

The rainforest is bursting with fruit this month, which can be found from the canopy, all the way down to the forest floor. Particular fruits to look out for include the 'beans' of the Black Bean, 'plums' of the Cassowary Plum and fruits of the Walking Stick Palms and Scented Daphne.

The Black Bean, also known as the Moreton Bay Chestnut, belongs to the Fabaceae family, one of the largest families of flowering plants. It is a common shade tree around Cairns, and occurs naturally throughout rainforests from NSW to the tip of Cape York Peninsula and Vanuatu.

Growing up to 35m tall, the Black Bean (Castanospermum australe) is a large tree in the forest, which is easy to identify in September / October, thanks to its red / orange, pea-like flowers. The flowers are followed by fruits, seeds resembling large beans, encased in chestnut-like pods, which can now be seen at Skyrail.

Despite these seeds being very poisonous, they were a traditional food source for Aborigines, who valued their protein, fat and fibre content. To remove the toxins and make the seeds edible, they were steamed, then sliced very finely and rinsed in running water for two to three days before being pulped and eaten like rice. Note: This is a simplified version of the traditional preparation techniques: we do not recommend anyone eat Black Bean seeds, without the correct preparation.

The Cassowary Plum (Cerbera floribunda) is another tall rainforest tree (grows to 30m) now fruiting at Skyrail. These large, blue fruits contain a sap which is poisonous to humans and most animals, except the endangered Southern Cassowary.

The Cassowary's stomach is filled with a rare combination of digestive enzymes, which make it immune to the toxic alkaloids of the Cassowary Plum fruits. This is lucky for the tree, as the Cassowary is the only bird large enough to eat the fruits intact, which assists with seed dispersal and germination for the Cassowary Plum.

Another food source for the Southern Cassowary, are the smaller, red fruits of the Scented Daphne (Phaleria clerodendron). At Skyrail, this understorey shrub can be seen at Barron Falls Station, growing adjacent to the Rainforest Interpretation Centre.

Growing between 3-8m tall, the Scented Daphne is an open, multi-stemmed shrub with dark, glossy green leaves. All parts of the plant are considered poisonous to humans, including its perfumed, white flowers which can appear throughout the year, but most usually in November, on the examples growing at Skyrail. The Cassowaries seem to enjoy the soft flesh of the red fruits.

Another understorey plant fruiting at Skyrail this month is the Walking Stick Palm (Linospadix monostachya), at Red Peak Station. These red fruits are edible for humans and are sweet with a peppery aftertaste.

The plant's common name comes from its strong, flexible 'cane', which can be used as a walking stick. Rarely growing taller than 2m, the Walking Stick Palm has a crown of weeping fronds and is popular with gardeners and also as an indoor plant.