This can be a large and shapely tree to 20 metres or more under good conditions, or a stunted, almost bonsai shrub under harsher conditions.
Formerly known as Pleiogynium solanderi, the Burdekin Plum has a dark grey trunk and often glossy, compound leaves. This tree can be found in vine thickets, gallery rainforest and along creek lines in tropical Queensland and Papua New Guinea.
Even within a small area, Burdekin Plum can be extremely variable in appearance and the fruit vary considerably in size, colour and taste. In the wild, fruiting occurs in the winter months and seeds are apparently dispersed by flying foxes and wallabies. As with its close relative, the Mango, the flowers are small and insignificant.
Seeds germinate readily if they have been soaked in a bucket of water for 24 hours prior to planting. Burdekin Plum can be a little slow in the first couple of years, but soon puts on some fairly rapid growth. Eight years seems to be the minimum age for fruiting. However, grafting may produce some interesting effects. Burdekin Plums are widely grown in Townsville gardens and revegetation projects.
The fruit were popular with Aborigines, explorers and settlers, but seem to have fallen into disuse some time after World War II. They are fortunately experiencing a revival.
The large, black, globular or pumpkin-shaped fruit vary in taste. Those that have red-purplish flesh are quite tart, those with a pale greenish-white flesh are milder but less tasty. Some fruit are half red - half white, and these are delicious! This variety occurs naturally around Townsville.
The riper the fruit, the less unpleasant the drying effect of eating the fruit. In the centre is a large pitted stone which usually fills 70-80% of the total fruit. They do not ripen on the tree, but must be stored, either buried in sand or kept in paper bags in a dark spot for a few days.
They can either be eaten raw, cooked into jam or jelly, used to flavour meat, or to make wine. A ripe fruit is mostly water (73%), but has moderate levels of energy, fat, vitamin C and is high in fibre and most minerals. Analysis has shown that, like tree shape and fruit colour, the nutritional content is extremely variable between trees.
Experimental plantations are being established and there seems to be enormous potential for selecting superior varieties and grafting. The timber is regarded as one of the best native timbers by wood turners, who prefer to salvage fallen trees rather than cut down such a useful tree!
Look for old seeds underneath the tree. They look like little UFOs with portholes in the side.
Burdekin Plum is in the family Anacardiaceae, along with Mangoes and Cashew Nuts.
(Reprinted from "The Native Gardener", SGAP Townsville Newsletter, August 1997)