Some time ago, I was looking at seedlings of this tree in the Crows Nest Community Nursery (where they were planned for a revegetation project), and wondered if I would recognise the plants in the wild.
The answer, I discovered while bushwalking last week, was that I would not, until they bit me!
They actually have very few stinging hairs, so (as you can see) I handled them for some time without being aware of their identity. Then I moved a leaf in such a way as to brush the central vein on the back of the leaf, which is apparently where stinging hairs are most likely to be found, across two of my fingers.
Gwen Harden, Bill McDonald, and John Williams, in their excellent field guide “Rainforest Trees and Shrubs” (Gwen Harden Publishing 2006) describe the plant as having “hairs stinging, but not violently so”. My opinion is that they were at least as violent as those of the giant stinging tree (Dendrocnide excelsa), though admittedly the effect had worn off entirely after four or five hours. Perhaps the reason that this is a less dangerous stinging tree than its larger-leafed cousin is simply that any individual sting is likely to be the result of contact with only a few stinging hairs, affecting only a small section of skin.
In the same spot, there were plenty of small cunjevoi (Alocasia brisbanensis), whose juice is supposed to be a cure for this sting.
(See May 7, 2010 for more about cunjevoi.)
In the name of science, I applied a generous amount of the juice from a leaf-stem to one suffering finger, leaving the other untreated. I’m sorry to have to report that there seemed to be no difference, either in the pain or in the recovery time, between the two fingers.
Several of my bushwalking companions were also stung as they brushed past plants in the scrub, failing to notice them even after we had discussed the plant. Not all the leaves were as obviously toothed as these ones, and the foliage was easy to mistake for that of young bollygums (Neolitsea dealbata), which were also plentiful.
You can see on the photo above that the back of the stinging tree leaf is green, as opposed to the white back of the bollygum leaf below. It also has a characteristic pair of domatia in the angle of the lower leaf veins. (Double click for a closer look.)
This plant can become a 30m high tree, with a buttressed trunk. It is usually found in dry rainforest. Its succulent white fruits grow in densely tangled masses. (Technically, the actual fruits are very small, and the succulent bit is the swollen stem of the fruit.) They look delicious, and people are said to eat them, after tossing them in a paper bag to remove any stinging hairs. Apparently they taste like green apples - but putting a thing like this in your mouth seems a bit silly, to me. I imagine that one remaining stinging hair, affecting the mouth or throat of a sensitive person, would have the potential to cause serious harm. Best to leave them for the catbirds!