Davidson’s plum (Davidsonia jerseyana) and the smooth Davidson’s plum (Davidsonia Johnsonii) are both endangered fruit species indigenous to a small pocket on the eastern Australian coast, largely based around the crater shell of the extinct volcano Mt Warning, near the New South Wales/Queensland border.
The smooth plum gets its name because its leaves are smooth, unlike those of the plum which are larger and hairy. Both trees grow between 5-12 meters in height and have small flowers that are pink, dark pink or red. The fruit of both is dark purple to blue-black in colour. The plum can grow from seed, whereas the smooth plum grows by suckering, its seed being infertile.
Both species of Davidson’s plum have been a staple in the diet of indigenous Australians living in the area, for tens of thousands of years. They were eaten raw and also were used for traditional medicinal purposes. The tree trunks were also utilised to make harpoons for catching turtles and hunting dugong (a marine mammal).
The Davidson plums are under increasing threat of extinction. Habitat alteration and fragmentation through the clearing of large areas for agricultural activities and urban development has destroyed or isolated many Davidson’s plum populations. Many trees are remnants, left growing in isolation in land converted to pasture, where a combination of dense pasture grass, grazing and trampling inhibit or prevent regeneration from these isolated trees, and open-sites provide unfavourable conditions for seedling development. Cattle often destroy flowers on the lower section of the trees. These isolated trees have little chance of reproduction, pollination or seed dispersal, and so gene flow between many tree populations may have ceased. Exotic weed invasion also threatens this native species, particularly Camphor Laurel and Lantana, which is capable of smothering both juvenile and adult plants.