Weed and pest control

Spraying of chemicals is carried out over Porirua for a variety of reasons, including managing invasive weeds on quality sports surfaces and placing a fungicide on our significant rose garden beds.

Typically, the need to spray in our parks, open spaces and our roads and footpaths is a fundamental operation to ensure we can keep our spaces looking tidy and at a standard that the community (and our staff) can feel proud about.

Alongside this we identify areas where not to spray and often don’t spray.

To continue to understand the questions around why we use spray, below we break down by our different functions to further understand the need and result if we were to not spray:

Yes, we do. It’s important for our staff and contractors to make an informed decision as to when it will take place, taking a number of things into consideration. All staff and contractors are Growsafe certified and get training and follow procedures in accordance with proper guidelines.

Weeds – (any unwanted species)

Tracks and reserves

Our walking, commuter and coastal tracks are key attractions for locals and visitors to Porirua. Data shows that they are well utilised by walkers, runners, and cyclists.

Track edges are sprayed to keep the path edges clear and clean of any intruding invasive weeds or plant growth. By doing so, this ensures that the track is clear and safe for users as well as increasing the lifespan of the asset – it also reduces the amount of maintenance required on an ongoing basis.

On a larger scale, more significant weed plants may be near tracks, walkways and reserves that need eradicating, and this is done as a preventive measure to stop any conflicting vegetation to enter the carriageway of the tracks or path and reserves

For hard surface paths such as concrete or asphalt, it’s important to keep these surfaces clear of any potential slippery coverings as this becomes a health and safety issue.


Porirua is full of beautiful and special gardens that the community admire as they either drive or walk past. We’re constantly receiving positive and constructive feedback about these spaces and know that they are well valued because of the condition they are kept in.

Spraying in these areas help to kill off any unwanted plants or weeds and to ensure good flower and plant growth is prioritised and maximised.


Whenua Tapu, Porirua Cemetery and Pāuatahanui Burial Grounds are special places for members of our community. They’re sacred spaces that we strive to ensure are always looking at a premium level.

Like other teams, the Cemetery Team undertake spraying to ensure different sections of their spaces are kept weed-free, clean and tidy. This includes maintenance of pathways, open grass areas and garden maintenance.

Sports fields

Our city’s sports fields are well-utilised and visited by not only our own community, but also visitors from outside Porirua due to the nature of competitive sport. In addition, we’re always aiming to provide top-quality surfaces to ensure that high level sport recreation can happen. For this to happen, certain types of spraying are required to keep us up to standard.

At our two premier fields, Porirua Park and Endeavour Park, we use chemical control on Poa annua (unwanted grass species). There are two types of growth regulator control: A post-emergent is used every 6-8 weeks depending on seasonal growth and is used in conjunction with a pre-emergent which is used twice per year when the turf gets renovated and more seed sown.

These regulators are used to keep the surfaces performing at their best for the highest level of sport and are a critical form of control to do so.

All sports fields are broadleaf weed controlled early spring before renovations. It usually takes place in the gap between end of winter and beginning of summer sport but weather dictates the best timing.

Amenity mowing areas

Amenity turf spraying is mainly around the Porirua CBD. Since we started spraying the broadleaf and selectively spaying undesirable grasses (eg paspalum), the CBD has seen an overall improvement of presentation. Other amenity areas edges are sprayed as required to reduce maintenance once or twice per year. Other amenity turf areas such as Te Rauparaha Park is broadleaf week controlled along with the sports fields.

Play spaces and fenced dog exercise areas

Playgrounds-only spraying is on the wooden structures to remove moss, mould, and lichen to make the structures safe. A build up on these surfaces, if not controlled, can be slippery and pose a safety issue. A monthly audit is undertaken, and the areas treated as required. We use a thermal weed treatment which uses hot water to eradicate weeds in the playground and fenced dog exercise areas. https://www.weedingtech.com/nz/

Butterfly walkway garden, Aotea Lagoon

Pesticides have not been used in this highly visited area in Porirua. As a way to get the levels of aphids to a manageable level without causing harm to the plants there (such as swan plants), we have introduced parasitic wasps and Tasman lacewing. In conjunction with this, flower species that provide food and shelter for these insects have been planted and since these two actions, the aphid population has reduced – this is an example of eschewing traditional pesticide methods to get a positive outcome.

Read an article on not using pesticides in the butterfly walkway garden here.

Porirua's roads and footpaths

Find out more on our road maintenance pages

For more information, please email [email protected]