Dual benefits for growers with native planting

This feature story is from the July 2025 edition of NZ Grower & Orchardist.

Native plantings to reduce sediment flows into the Kaipara Harbour are set to also provide growers with pest management benefits, using knowledge from an A Lighter Touch biodiversity project.

Earlier this year Horticulture New Zealand, through its Growing Change project, partnered with Kaipara Moana Remediation (KMR) to support growers to take up KMR practical projects. These include fencing and native planting programmes to promote on-farm biodiversity, improve soil management practices to reduce overall freshwater impacts and contribute to wider freshwater improvements in the Kaipara Moana catchment.

Through this partnership, KMR planting specialist and nursery liaison David McDermott became aware of the A Lighter Touch (ALT) programme, and the plant species resource produced from the biodiverse planting on vegetables farms project. This project, an ALT partnership with Vegetables New Zealand and Onions New Zealand, aims to demonstrate increasing plant biodiversity on vegetable farms can result in more beneficial species, fewer pests in crops, and less pesticides required.

The project involves three biodiverse planting components, one of which is native perennial planting. The native species selected are designed to provide food and habitat through winter to support key beneficial populations, which in turn contribute to pest suppression in the vegetable growing system. The project’s location in Pukekohe also factored into the native plant selection.

David says he’s a “bit of a plant nerd” and when he discovered the ALT native planting list, it got him thinking about what a native species mix for pest management benefits might look like in a Kaipara catchment context.

He loved the concept of encouraging biodiversity in order to reduce chemical inputs and was keen to see if the KMR programme could support growers in realising pest management benefits from their planting, in addition to the native plantings’ primary purpose of reducing soil sediment flows into the Kaipara Harbour.

There were some native species in common across both the KMR and ALT planting lists, and David was interested to see what other species could be added to the KMR mix. However, he had to be conservative in choosing what to add.

“With KMR, we’re planting at large scale and we’re typically using species that are going to do well in the open, they’re hardy as. We have to be super mindful about survival in our species selection.”

That said, there were some extra species in the ALT list which were a great match both in terms of supporting KMR’s sediment reduction objectives and being hardy enough to include in the planting mix.

“The pōhuehue is a really awesome plant, it’s great for controlling and reducing bank erosion, plus the bees and other beneficial insects love it too. It’s a total winner for this situation.

“Also, pinātoro (New Zealand daphne) is well suited to the free-draining soils of the Kaipara eco district and is pollinated by a variety of insects, including native bees, butterflies and moths. We’re also including lots of the usual suspects (in the KMR plant mix) all of which offer various biodiversity, shelter and soil conservation values,” David says.

A Lighter Touch agroecological technical lead Jeff Smith says the synergy between the two programmes is a real win for growers in terms of being able to achieve multiple benefits from the native planting.

He says there’s also another significant benefit in that KMR is helping to regionalise the native plant list in a vegetable growing region.

“Part of the extension of our biodiversity project is to have satellite sites in key vegetable growing areas around the country, and we have a group of grower champions who are supporting that work by trialling the biodiversity components we’ve demonstrated at the Pukekohe Research and Demonstration Farm.

“Our project technical lead Olivia Prouse has been working with growers in other regions to tailor the plant species list to their specific region, and this collaboration with KMR is another step forward in that work which will benefit Northland vegetable growers.”

One of the ALT biodiversity project’s grower champions is kūmara grower Luke Posthuma, who farms near Te Kōpuru, south of Dargaville, within the Kaipara Moana catchment. Luke is also part of Horticulture New Zealand’s Growing Change project, which has supported growers in getting a headstart on freshwater farm plan regulations, and has taken up the opportunity to do native planting with KMR.

Luke trialled annual flower strips to increase biodiversity on his farm last season, and having seen pest management benefits from that trial, was considering the use of flowering natives in non-cropped areas as his next step.

The KMR-Growing Change partnership has super-charged his native planting ambitions. Thanks to 50% funding from KMR, and 40% through Growing Change, Luke will see almost a hectare planted this winter with about 9,500 natives established on land he regards as waste areas of the farm.

“We’re planting along the drain banks, and we’ve got some mud springs which flow into our cropping area. It’s right on the margins of where we’re cropping. We’re also doing a bit of wetland planting and riparian planting,” Luke says.

“In heavy rain, we can lose quite a bit of topsoil down the hill, so the planting will act as a buffer and will stop any sediment getting into the drain.”

Luke sees great value in being able to achieve dual benefits to his farming system from the native plantings, through selection of species which support pest management benefits, and well as reducing soil erosion and sediment flow.

I’m a young grower, and I think insecticide resistance is only going to become a bigger and bigger problem. If we can get natives planted now which will encourage beneficials, I’m creating a habitat to always have a source stock of them.

“Even if we’re only doing trials for the next 10 years learning how to get best use of beneficials, I can be fairly confident I will have beneficial insects in early spring. Our place is pretty barren, we don’t have many trees on it, we’re surrounded by dairy farms, with a lot of grass and a lot of grass weeds. This native planting is going to create a source area for those beneficial insects to come out of.

KMR has been planting with pastoral farmers around the Kaipara Harbour in Northland for the past two years, but as part of the partnership with Horticulture New Zealand and Growing Change it is now extending into horticulture.

Arjune Dahya is Project Lead for the Growing Change Northland Catchment Project, which identified the potential for collaboration with KMR. He sees the partnership as an exceptional opportunity for Northland growers to use the Growing Change funding to assist them in meeting freshwater farm plan requirements and carry out practices to improve on-farm sediment and erosion control measures.

“It’s really aligned what Growing Change and KMR were both striving to achieve in the Kaipara Moana, and it’s such a positive outcome for our growers,” he says.

Nine kūmara growers have signed up so far, which will see 33,000 natives planted this winter across 7.3 hectares. In addition to the planting, the Horticulture New Zealand and KMR joint project has also already contributed to 4.5km of fencing of waterways, drains and existing native bush on these properties. Contracts for a further 4km of fencing are being finalised.

Based on the level of interest seen so far, the number of horticulture growers involved in the programme will continue to expand next winter. It is growth welcomed by KMR Pou Tātaki (chief executive) Justine Daw.

This project will support the restoration of the Kaipara Moana and promote horticulture best management practices. Our goal is to support increased resilience to future climatic events such as floods, cyclones and storms, increase environmental stewardship and improve social cohesion and resilience across participating rural communities

Vegetables New Zealand vice chair Warwick Simpson is one of the first kūmara growers in the Kaipara catchment to work with KMR, with 3700 natives going in the ground on his farm in June.

The plantings have gone in alongside drains and also along his farm’s western boundary to help prevent the prevailing wind from contributing to soil loss during cultivation. He says some of the drain-side plantings are located in the middle of his farm, a handy location in terms of also providing habitat for beneficials in close proximity to his crops.

Warwick and Luke both emphasise the importance of the financial support through KMR and Growing Change. “The 90 percent funding from KMR and Growing Change is huge because the trees are pretty expensive, that funding has totally made it happen,” Warwick says.

Luke agrees, saying he is happy to do the spraying and fencing required in preparation for the planting, but in the current economic climate, he wouldn’t have proceeded with the planting without the costs of the plants and fencing materials being covered.

KMR’s David McDermott appreciates that for many growers the idea of retiring land for native planting is quite radical. “Starting off with a really generous offering that can get some people on board to show the value to others, I think it’s a really good approach.

“And forward-thinking growers are seeing the change happening, they want to be part of it, doing the right thing. While the support’s there, it’s a great opportunity because with co-funding like this, there’s no guarantees it will be there forever.”

KMR is the largest harbour restoration initiative in New Zealand and one of the largest catchment groups in the country. It invests in projects to restore wetlands, fence off rivers and streams, plant trees and regenerate forest on erosion-prone land with the long-term aim of halving sediment flows into the Kaipara harbour.

Growing Change is a three-year partnership between Horticulture New Zealand and the Ministry for the Environment (MfE). Funded through the Essential Freshwater Fund, administered by MfE, it aims to build capacity and capability within the horticulture sector, and enduring support for growers, to deliver GAP freshwater farm plans.