August in the forest with Chris Horne and Barbara Mitcalfe
Urtica ferox Ongaonga Tree nettle
Our well-known NZ stinging nettle, ongaonga, Urtica ferox, is one of over 1000 species in the worldwide nettle family, Urticaceae. It is one of nine indigenous NZ nettle species. Not all nettle species sting - many have medicinal properties; some can be eaten, providing a good source of Vitamin C, and NZ and non-NZ nettle species are hosts for red admiral butterflies.
But before we go any further - yes, the substance injected at your slightest touch, by ongaonga's “hypodermics”, (technically, stinging hairs), is a potent, nerve toxin. It causes the victim's body to react instantly with an extreme histamine response. Too much of it has proved fatal to humans and some animals, dogs and horses in particular.
Most trampers are likely to have experienced the acute pins-and-needles tingling, alternating with numbness, which can last intermittently for 2 – 3 days, after an encounter with ongaonga. You can use antihistamine ointment from your first aid kit to reduce these symptoms, but if respiratory or muscular coordination symptoms occur, seek medical help. Infants and young children need to be kept well away from ongaonga.
Make a point of teaching children, and visitors to NZ, to recognise this twiggy shrub which grows from 1 to 3 m high, often found in sunny places at bush margins. Its pale green, serrated leaves are usually c.12 cm long by 3-5 cm wide, and the minute flowers are crowded on fine, dangling twigs. Leaves and stems are armed with white, stinging hairs, each hair fed by a tiny bladder of toxin.
Keep an eye out for Urtica incisa, another NZ stinging nettle species common around Wellington, looking just like a small version of Urtica ferox.