Science & nature
Beware the Tree Nettle

Many of us have childhood memories of being stung by a Nettle, in a garden, bushland or a random wild urban area. 

Nettles, or plants in the genus Urtica, generally appear as low herbaceous (non-woody) plants, either annual or perennial, and they occur everywhere from Asia, Africa and Europe to the north and south Americas. Their leaves are often present just at the right height for a child's hand to brush past and garner a painful sting.

Australia is home to a single species of native Nettle, Utica incisa, which is a very pretty plant if you leave aside its stinging tendencies; there are also introduced Nettle (Urtica) species, more common in gardens and urban areas. 

But in Australia the word Nettle has a much wider, or should I say higher, application, as this continent is home to some truly massive plants in the same family as the common-or-garden Nettles. These are the Dendrocnides, or Tree Nettles. In this region, the Giant Stinging Tree (Dendrocnide excelsa), can grow to 30 metres or even 40 metres high, with a trunk that can be 2m or more in diameter in very old trees.

And if you think the Stinging Nettle packs a sting, then be very, very wary of the Giant Stinging Tree. Its leaves, flowers, fruit and stems are all covered with stinging hairs that can deliver a very painful, long-lasting sting. 

The large juvenile leaves of Giant Stinging Trees (Dendrocnide excelsa) can often be seen growing on shoots coming off the trunks of established trees, and may be present alongside bush tracks. Beware! Photo: Emma Rooksby. 

It is worth pointing out that pretty well every part of the Giant Stinging Tree can sting, but that the large juvenile leaves that often grow close to the ground, are often especially well-endowed with stinging hairs. 

The trunk is an exception, and the soft almost-corky looking bark poses little risk to the touch. But, unfortunately for us humans who like to clear a path to walk, damaging a trunk or exposed root of a Giant Stinging Tree often prompts the tree to respond by putting out new shoots and leaves, covered with those problematic hairs. 

Even the flowers and fruit of Giant Stinging Tree can deliver a painful sting. Some insects however manage to munch on the leaves without harm, as this picture show. Photo: Denise McConnachie. 

If you see large round soft hairy-looking leaves growing alongside the track on your walk, or fallen onto the track itself, give them a wide berth! And beware, even the dead leaves can give you a nasty sting.

Some common first-aid treatments for a Stinging Tree sting include application of native dock leaves and topical pain killer, but the most effective treatment I've found is to apply wax hair-removal strips, which can stick onto and pull out the painful stinging hairs. We are also fortunate that Giant Stinging Tree doesn't deliver as painful a sting as some of the other Australian Dendrocnides; Gympie Stinger or Dendrocnide moroides is reputed to cause incredible pain.

Stay safe while bushwalking.  


Emma Rooksby is the co-ordinator of the Growing Illawarra Natives website

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