Understanding key plant terms

When researching weeds, you’ll come across plenty of technical terms. Here are some quick definitions to help:

• Alien or exotic species – a non-native plant brought into New Zealand (on purpose or by accident).
• Endemic – native plants unique to New Zealand and found nowhere else in the world.Blue morning glory is a example of a ‘garden escapee’ species
• Garden escapee – plants introduced for ornamental reasons but has ‘jumped the fence’ from gardens and spread into natural areas.
• Native or indigenous – Plants that are naturally found in New Zealand (not introduced accidentally or deliberately by humans).
• Naturalised – a non-native plant that has spread on its own in the wild (without help from humans).
• Noxious weed – an outdated legal term that dates back to the Noxious Weeds Act 1950. The act was replaced with the Biosecurity Act 1993, our main biosecurity legislation in Aotearoa New Zealand.

Different weeds, different impacts

Not all weeds behave the same. Some thrive in multiple environments, while others pose challenges in specific land uses:

• Agricultural weeds threaten farmers by reducing crop yields, outcompeting pasture species are often not edible for livestock.Alligator weed impacts aquatic environments - clogging waterways and outcompeting other desirable species.
• Aquatic weeds clog up freshwater lakes and rivers, harming fish and aquatic life. They can alter water flow, increasing the risk of flooding and block key infrastructure such as hydro dams.
• Dune weeds destabilise coastal sand dunes, worsening erosion.
• Environmental weeds invade native vegetation and are harmful to native ecosystems and/or biodiversity
• Horticultural weeds cause problems for growers, competing with fruit and vegetable production.
• Marine weeds disrupt coastal ecosystems and marine biodiversity.
• Riparian weeds smother stream banks, threatening water quality and native species.
• Wetland weeds invade swamps, bogs, and marshes, choking out native wetland plants.

Pest plants: terminology can be tricky!

A ‘Pest’ is a legal status, not just a nickname. Some pest plants are classfied Unwanted Organisms regulated by the Ministry for Primary Industries and others are listed as pests under Regional Pest Management Plans managed by Regional Councils.

Under the Biosecurity Act 1993, it is illegal to breed, propagate, sell, release or move a legally declared pest plant.

Even if a weed isn’t officially a ‘pest’, it can still be harmful and should be taken seriously.