In North Queensland
by Greg Calvert
In the last ten years there has been a massive upsurge of interest in edible native plants, known by many as “Bush Tucker”. While there is a series of tests which can be conducted on fruits to determine if they are edible, there are several species which enthusiasts should be aware can do serious harm if experimented with.
Finger Cherry (Rhodomyrtus macrocarpa):
When I was first learning about edible plants, I taught myself a rule: “If it is a fleshy fruited plant in the huge Myrtaceae family, then it is edible”. This is true for all of these eighty plus trees and shrubs in Australia, except for possibly one species.
The Finger Cherry or Native Loquat is a common rainforest tree in the Wet Tropics and Cape York Peninsula, with large leaves and spectacular crops of bright red cigar-shaped fruit with numerous seeds. Under the careful supervision of an Aboriginal elder (whose botanical knowledge I trusted completely), I skinned and tasted one of these fruit. It was absolutely delicious! Possibly one of the nicest eating of all the Cape York Bush Tucker and they certainly pass all the taste tests for toxic plants.
The problem is that people who have gorged themselves on this fruit have gone suddenly and irreparably blind, and there is no cure or treatment known. Aborigines on Cape York inform me that they have eaten this plant all their lives and have never heard of nor seen these drastic symptoms. In Hopevale, near Cooktown, Aboriginal elders say they used to skin or roast the fruit prior to eating it, but stated that they felt it was “like playing Russian roulette”.
Authorities are at a loss to explain the plant’s toxicity. Some suggest that unripe or partially ripe fruit are the culprit. It is actually quite common for plants to load their unripe fruit with toxins to deter premature dispersal. The other theory is that there is some sort of fungi growing on the skin of the fruit. Whatever the reason, this is a plant for all enthusiasts to be aware and beware of.
Cycads (Cycas, Lepidozamia, Macrozamia spp.)
The large plump nuts of the palm-like cycad tempted many early explorers into giving them a taste. The results were punishing, to say the least, causing violent eruptions from both ends of their bodies.
The Dutch explorer, de Vlamingh, recorded in 1696 that “The sailors who ate these nuts crawled all over the earth and made ungovernable movements”. Cattle graziers also consider the plants a pest, pointing out that cattle which feed on the plants become “rickety” and lose coordination of their movements before finally dying. This is because the cycad nuts contain powerful neurotoxins that disrupt and interfere with nerve messages.
Surprisingly enough, these nuts were a staple diet of the Aborigines whose traditional knowledge included how to roast and process the seeds to remove these toxins. The seeds are, after all, very high in energy, fat and carbohydrates. This practice is also carried out in Papua New Guinea, Irian Jaya, Guam and the Kii Peninsula in Japan.
Medical researchers recently discovered a rare neuro-degenerative disease called “Western Pacific Parkinsonism-dementia” (also known as “Guam Disease”) amongst those people whose traditional diet includes cycads. Apparently, a long term, slow acting toxin from partially treated nuts is the cause of this crippling degenerative disease. It just goes to prove that even if you think you have succeeded in processing the nuts to the point where they cause no immediate effects, the toxins may still catch up with you in the years to come!
Native Cashew (Semecarpus australiensis).
Most people relish and adore the delicious nuts of the Cashew Tree (Anacardium occidentale), yet few are aware that the nuts are actually toxic without prior preparation. The exotic Cashew does, however, have a large and fleshy ‘apple’ to which the nut is attached. This ‘apple’ is extremely delicious, makes great wine and preserves and can be eaten without any treatment necessary.
People’s familiarity with the Cashew tree also drives many people to take an interest in our own Native Cashew. Like the commercial species, the nut is poisonous. However, our native species is much more extreme than that grown on farms. The point of attachment between the ‘apple’ and the nut bleeds a black resinous substance that can strip the chrome plating off car keys and strip paint off a car parked beneath the tree. Needless to say, contact with this sap can cause deep and painful ulcerations, as it did to explorer Ludwig Leichhardt, who experimented with the fruit.
Some people have assured me that the ‘apple’ is harmless, yet I have seen black patches of sticky resin appear on the surface after I have scratched the skin. The damage to your throat that would occur from eating this fruit does not bear imagining.
Not only the fruit is toxic. The entire plant is capable of causing severe contact dermatitis in sensitive people. A friend of mine was recently conducting a botanical survey of Yam Island in the Torres Strait, when he encountered this tree. He took a bark blaze, collected some foliage for his plant press and handled some fruit. The next day he was airlifted back to Cairns hospital with extreme lesions and blisters over much of his body.
Stinging Tree (Dendrocnide moroides).
Also known as Gympie-Gympie, this is one of the most feared plants of the rainforest. Fortunately, it is easily recognised, so that most people who are stung are those who are ignorant about plants and their identification. Kind of sweet poetic justice really.
The leaves and stems of the plant are covered in hollow glass needles filled with a highly irritating toxin. Merely brushing against this plant can cause excruciating pain, which recurs every time that part of the body gets cold. This can continue for up to a year!
Many people are sceptical about the edibility of the fruit, yet I can assure them that they are indeed edible, though quite bland and watery. The dangerous thing about the fruit is that they too are covered in dangerous hairs.
To eat them, the fruit are knocked off the shrub with a long stick, then gathered up in a piece of rag or hessian cloth. The fruit are then rubbed vigorously within the cloth to knock off any of the hairs. The fruit are irregular in shape and some hairs may still persist. I find it a good policy to pull them apart and rub them with bare hands. It is, after all, a far better thing to be stung on the hands than in the mouth or throat.
I am sure that most would agree that this is a lot of trouble and a large amount of danger for eating a fruit that has little to recommend it anyway. Having been badly stung myself while collecting fruit, I would advise leaving it well alone.
(Reprinted from “The Native Gardener”, newsletter of the SGAP Townsville Branch, November 1999 & February 2000)