Tree Nettle

Urtica ferox, commonly known as tree nettle and ongaonga, is a species of nettle endemic to New Zealand. A member of the Urticaceae, the plant is covered in trichomes (hairs), which contain toxins that are poisonous to humans and other animals. It is a large woody shrub or small tree that can grow to a height of 3 metres (10 feet). Its trichomes can cause painful stings, with effects that can last several days or weeks; the sting is strong enough to kill cattle, dogs, and horses. Two human deaths have been caused by contact with the plant.

The plant was first scientifically described by German naturalist Georg Forster in 1786. U. ferox is wind-pollinated, and its seeds are later dispersed by gravity or the wind. The plant serves as a host for several moth species, and it is the primary source of food for the larvae of the New Zealand red admiral butterfly. Despite being a plant usually avoided by people, U. ferox has some traditional and medicinal uses for the indigenous Māori people. Its 2023 assessment in the New Zealand Threat Classification System was not threatened.