Weeds in New Zealand

What is a weed?

A weed is a plant growing where it is not wanted and with a harmful impact. It can be harmful to human activities, such as farming or recreation, or it can be harmful to New Zealand's unique environment. Weeds are usually plants that have been introduced to New Zealand by people.

Economic weeds are plants that are harmful to money-making activities such as agriculture or forestry. Environmental weeds are plants that invade native vegetation and are harmful to native biodiversity and/or ecosystem functions. Many economic weeds are also environmental weeds.

Weedy Examples....

Economic Weeds

Environmental Weeds

Ragwort (Senecio jacobaea)

Weed of farms throughout NZ
Poisonous to livestock
Can also invade important environments such as riverbeds and open forests

Broom (Cytisus scoparius)

Weed of farms throughout NZ
Invades plantation forests and competes with young trees
Also an important environmental weed, particularly in open vegetation such as South Island tussock grasslands
Invades unique braided rivers (pictured above) and destroys habitat for waterbirds

Gorse (Ulex europaeus)

Weed of farms throughout NZ
Invades plantation forests - competes with young pine trees & hampers pruning and thinning
Also an important environmental weed, particularly in low-growing vegetation communities

Buddleia (Buddleja davidii)

Weed of pine plantations
Also invades native vegetation communities

Pampas grass (Cortaderia selloana)

Weed of pine plantations
Also invades many different native communities, such as dunes, wetlands and cliffs - outcompetes native plants in these communities

Madeira vine (Anredera cordifolia)

Smothers native trees (and lamposts!!)

Wilding pine (Pinus spp.)

Wilding pines have spread from forest plantations or shelter belts and can shade out low-growing vegetation and replace the native plants in grasslands or shrublands with a monoculture of pines (e.g., Pinus contorta in Tongariro National Park.
Pines (Family Pinaceae) from the northern hemisphere can tolerate cold conditions better than native trees and can shade out native herbs and shrubs above the native treeline
Some exotic pines, such as Douglas fir (Pseudotsuga menziesii) can tolerate shade and can invade native forest

Heather (Calluna vulgaris)

Has replaced much of the native vegetation in parts of Tongariro National Park

Wild kiwifruit (Actinidia deliciosa)

Kiwifruit seeds are spread by birds and wild kiwifruit vines can smother native trees (photo: wild kiwifruit vine strangling a native mahoe tree (Melicytus ramiflorus) in Bay of Plenty)

Mist flower (Ageratina riparia)

Smothering plant that prevents native plant regeneration by shading out native seedlings
Weed of stream and forest margins

This website was prepared by Margaret Stanley to encourage teachers to use weeds as a learning context in their teaching, to encourage students to learn how weeds impact on New Zealand's unique environment and to apply their newly gained knowledge and skills to providing solutions to weed invasion in their own backyard or local reserve. More information on weed research is available on the Landcare Research web site.

Feedback: thank you for your visit! If you would like to ask questions about the information on this website please contact Lynley Hayes Email .

Acknowledgements: Thanks to Jo Stanley (Kavanagh College) for drawing some of the cartoons (the best ones!). Landcare Research's weeds researchers, Jo Stanley, Amber Bill, Gill Robinson, Esther Mae and Wendy Baker for feedback on various drafts of the material used on this website. Thanks also to David Hopkins for helping with artwork preparation.