What is a weed?
A weed is a plant growing where it is not wanted. Over 1,800 species of plants, many brought from overseas for New Zealand gardens, have spread in the wild. There, they can become pests, climbing over and smothering native plants.
Where they grow
Weeds do not usually thrive in dense, dark bush. They flourish at bush edges, in scrubland, and in open ground that has been damaged by animals, fire or slips. Seeds are carried by wind, water or on people’s shoes. When people dump garden waste near the bush, garden plants may take root.
Weeds can kill native plants, and deprive animals of food and shelter. The Department of Conservation lists about 300 weeds as serious problems in national parks and reserves. But it is expensive and difficult to control weeds. Volunteer groups such as Weedbusters help by pulling out weeds in problem areas.
Some bush weeds
- Woolly nightshade escaped from gardens in the 1880s and is now a common weed in northern bush. Nothing can grow beneath it, as rainwater dripping off the leaves is poisonous.
- Gorse was brought from Britain in the 1830s to make farm hedges. But it has taken over farmland, scrubland and damaged forest.
- Blackberry came with the first British settlers and quickly spread. Today, sprays help control it, but it is still a serious problem in some scrublands and forest reserves.
- Jasmine is a well-behaved garden plant south of Gisborne. But further north, where it is warmer, jasmine climbs up trees and smothers them.
- Old man’s beard has thick stems up to 30 metres long, which strangle trees. A single plant can cover the area of a tennis court. It is illegal to have this plant on your property.
- Wild ginger has exotic-looking flowers, but it has taken over some forest reserves in the north.