Naturalised plants

Naturalised plants in New Zealand include those that have established themselves in wild habitats, and plants that are spontaneously seeding or spreading vegetatively in urban environments.

Newly naturalised plants are documented by the publication of checklists that update the Flora of New Zealand series. These lists serve as a biosecurity watchlist for plants currently spreading in urban environments, with the potential to become pest plants in wild environments.

Checklist publication is a collaborative project involving botanists from Landcare Research, DOC, Auckland Museum, and NIWA.

Origins of naturalised plants

Polynesian settlers, the ancestors of today's Māori people, brought plants with them intentionally or unintentionally, some of which like Sigesbeckia orientalis became established as wild plants. Some weedy plants characteristic of the northern hemisphere, such as Rorippa palustris, were established here when Banks and Solander collected them in 1769, and perhaps were able to establish following human disturbance.

Large–scale introduction of European crops and garden plants after 1840 brought many attendant weeds and the number has steadily grown year by year (e.g. Heenan et al. 1998, 1999, 2002b, 2004a, 2008) with only a few losses. Origins and biology of the naturalised flora were reviewed by Healy (1969, 1973), Esler (1988), and Webb et al. (1988).