Wild ginger (Hedychium gardnerianum)
Wild ginger or ginger lily is originally from India and was first grown in New Zealand gardens in the 1920s. It grows to head-height, with a thick-rooted mat of stubborn rhizomes a metre deep. It has escaped from gardens to overrun forest reserves and displace native plants in Northland, Auckland, Waikato, Coromandel and Buller. It is also a prolific weed in Hawaiian forests.
Ragwort (Senecio jacobaea)
Ragwort was probably brought to New Zealand accidentally with pasture grasses. It was first recorded growing wild in Dunedin in 1894 and rapidly spread throughout the country, especially where cattle and horses were grazed. Ragwort also grows on the Kermadec and Chatham islands. It was declared a noxious weed in 1900.
No weeds on us
In 1947 the New Zealand Weed Control Society was established to help educate people about weeds. It later became the New Zealand Weed and Pest Control Society, and today it is the New Zealand Plant Protection Society. They publish papers and books on weeds and their control.
The plant grows especially well in areas of high rainfall and along bush margins. Although shade-tolerant, ragwort does not make headway into closed bush. If horses or cattle eat it, they may suffer cirrhosis of the liver, and die. Sheep are less prone to being poisoned by it when grazing, and help control the plant on some farms. In 1928, caterpillars of the cinnabar moth were introduced from Europe to control ragwort, with some success.
Clubmoss (Selaginella kraussiana)
This primitive creeping plant has slender, many-branched stems that form mats on the damp floor of bush margins or in regenerating forest. It grows so densely that it chokes smaller ground-growing plants. Clubmoss will grow from tiny stem fragments which, along with its spores, are easily spread on boots, by stock or machinery. Originally from South Africa, it was first noticed in New Zealand in 1919. Three species have been identified.
Wandering willie (Tradescantia fluminensis)
Also known as wandering Jew, this low-growing, brittle, dark-leaved plant puts down roots at intervals along its creeping stems. It smothers other low-growing plants. A native of Brazil, it was first noticed growing wild in New Zealand 1915. It prefers cool, moist, shady places, usually invading bush margins and damaged or regenerating bush.