Ongaonga
Tree Nettle
Urtica ferox
Their Story
Ongaonga (tree nettle) is one of Aotearoa’s most fearsome native shrubs — endemic, venomous, and beautiful. Found along forest margins and streams, its presence in the Brook Waimārama Sanctuary is a blessing and a pain. The plant is best admired at a safe distance.
This woody shrub can reach up to 3 m tall and has a broad, spreading growth. Leaves are pale green with large, coarse teeth, and stems, leaf veins and toothed edges are densely covered in white stinging hairs (trichomes). Contact with these hairs injects toxins, causing intense pain. New Zealand Plant Conservation Network+2Wikipedia+2
Primarily found in forest margins, riparian zones and open patches, ongaonga spreads via underground stems and regenerates after disturbance. Its stinging hairs protect it from many browsers. Ecologically, it plays a key role as the main host plant for the endemic Kahukura / New Zealand Red Admiral Butterfly (Vanessa gonerilla) larvae. Totopanen+1
Flowers appear from November to March in axillary clusters of male and female plants. Fruits are tiny brown achenes, single seeded dry fruits. Seedlings grow in moist forest floor conditions; mature plants may live for many years, continually regenerating from underground stems following disturbance. New Zealand Plant Conservation Network
Endemic to New Zealand, ongaonga occurs on both the North and South Islands and Stewart Island, in coastal to low-altitude forest and shrubland. Within the Brook Waimārama Sanctuary its presence contributes to structural complexity and supports biodiversity in the forest margin and stream-edge habitats.
Classified as Not Threatened, ongaonga has been cleared over much of its historic range, contributing to the decline of our endemic kahukura/red admiral.
Visitors walking through the Sanctuary’s forest edges may encounter ongaonga patches. Care should be taken not to brush against it — the sting is harsh.
🪶 The Māori word ongaonga also means “sting” or “irritation” — reflecting the plant’s painful spines.






























