Perennial nettle is a threat to both stock and economic well-being in Otago. It has a nasty sting that causes itching and burning, and animals shy away from it. Perennial nettle can easily invade paddocks and dominate farmland due to its large system of underground roots and ability to form tall dense stands. It can survive in a wide range of conditions, soil types and areas from shade and damp, to very dry. It can be found in pastures, in areas where stock shelter or gather, waste areas, river banks, roadsides and old house sites. It is a particular problem in South Otago, mainly Balclutha, Lawrence and Clydevale (along the Clutha River).

Perennial nettle’s stems are woody, its flowers are green and its leaves are a lighter green colour than common stinging nettle (Urtica urens). Perennial nettle can grow up to 1.5m high, which is taller than common stinging nettle. The seeds are flat, oval and yellow to greyish in colour. It has a widespread system of underground rhizomes (a continuously growing underground stem) that can spread 2.5m in a season. Common nettle does not have rhizomes.

Everyone in Otago must eliminate perennial nettle on the land they occupy. ORC staff inspect properties for perennial nettle from November to January.

ORC environmental monitoring officers are warranted, giving them legal authorisation under the Biosecurity Act to enter properties and inspect for pest plants.

You can spray with approved herbicides between spring and autumn when the plant is actively growing. Use herbicides at application rates recommended by the manufacturer and wear protective clothing. Alternatively, the plant can be dug out.

Control of this pest plant is not a one-off task. Follow up action must be regularly undertaken, e.g. checking a cleared site for rhizome regrowth and seedling establishment.

Caution: When using any herbicide or pesticide PLEASE READ THE LABEL THOROUGHLY to ensure that all instructions and safety requirements are followed.