What makes a weed?

Climbing asparagus
The tenacious climbing asparagus smothers vegetation

What is a weed?

Which weeds do you identify?

  • Weeds that get in the way of your garden plantings?
  • Your garden plantings that self-propagate and cause harm elsewhere?

Put simply, a weed is a plant where it shouldn’t be. The habitat the weed has invaded suffers, either directly, or over time as native species are out-competed. The subsequent loss of biodiversity from exotic plants has harmful follow-on effects. Controlling weeds costs ratepayers millions of dollars each year. Some weeds also cause allergies, skin rashes, or hay fever in both animals and people.

Pie chart
Source of weeds

How do weeds cause harm?

Weeds threaten our local native plants and environment by

  • reducing habitat, shelter and food for native fauna.
  • smothering and suffocating native forest and preventing regeneration.
  • altering soil conditions.
  • hybridising with local species and creating more problems at the genetic level.
  • clogging up waterways and affecting water quality entering the harbour.
  • speeding up dune erosion.
  • taking resources away from other important matters by being costly to control.
  • harbouring introduced mammalian predators such as rats, stoats, cats and hedgehogs which prey on our native wildlife.

Passport for travel

Today, over 75% of all weeds are garden escapes that have "jumped the fence". On average, eight garden plants become naturalised in the wild each year. More than 500 introduced plants are now serious weeds, and several are common on the Miramar Peninsula.

Many popular garden plants that are actually weed species will disperse their seeds via the wind and birds, and establish themselves kilometres away. They also spread via footwear, clothes, pets, car tyres and dumping.

Dumped garden rubbish often contains root fragments, cuttings and seed heads of invasive plants such as agapanthus and wandering willy/jew. Dumping green matter on roadsides or in the bush may seem like a biodegradable solution but it’s illegal and a sure-fire way to spread weeds. Please don't undo the hard work of eco-restoration volunteers and council staff.

Sadly, weed species are still arriving. Some exotic plants naturalised long ago, e.g., gorse in 1867; others naturalised more recently. Some plant species, such as bungalow, phoenix palms, bayleaf and kiwifruit may take up to 100 years before they overcome barriers and reproduce. We refer to these as 'sleepers'. They often spread slowly and go unnoticed until they are widespread.

Will the palms and trees like bay and kiwi fruit we plant now be New Zealand's worst weeds in 100 years and dominant in our native forests?

Plant pie charts

Which weeds are Miramar’s worst?

See our list of Miramar weeds.

Kahili ginger, cathedral bells, banana passionfruit, agapanthus, climbing asparagus, jasmine, honeysuckle and blue morning glory are among Miramars worst weeds. Karo and Karaka is also a weed on the Miramar Peninsula, even though it is native to other parts of New Zealand.

There are several aggressive weed strongholds around Miramar, especially on steep banks along the Worser Bay and Karaka Bay coastline. Morning glory and banana passionfruit can be seen in these places and there is a notable climbing asparagus and morning glory problem arising around the peninsula.

Around 80 % of all introduced vines that grow in our gardens cause problems in the wild. Ivy is an example of an ‘escapee’ weed spread from gardens through bird dispersal and dumped fragments.

Please don’t introduce these to your garden or ignore them if they grow in your surroundings. 

Stop the weed invasion!

You can easily play a part in preventing, or limiting, serious weed problems.

  • Learn how to recognize weeds and remove them wisely. With many weeds it takes more than just pulling them out. You’ll find useful information on this website and also at weedbusters.
  • Always take your garden waste to an approved landfill and use a tarp to cover your load, or burn it. Never dump garden waste. If you see a person dumping garden waste on council land report it to your local authority (ranger or regional council).
  • Stick with planting locally-native species to avoid the risk of new weeds arising from ‘escapee’ non-natives. If you feel you must plant a non-native, make sure it's not invasive by reading about it. You can also ask us or maybe a garden market.
  • Never plant in our natural environment without consent from the council, even if it is just opposite your house or a road reserve.
  • Join a local care group like ours, or Manawa Karioi Ecological Restoration Project in Island Bay, trellisick park and Miro to learn more about our local ecosystems and lend us a hand.
  • Share your knowledge of weeds with your friends and neighbours. Offer to help them, tell them about this website and remember to keep the conversation positive. No one likes to be blamed but most people will welcome friendly advice.