Low Cost Native Planting

Vet, ecologist, and farmer Dr Alison Dewes is the owner/director of Tipu Whenua, a sustainable land use consultancy. Alison is working across multiple projects around sustainable farming and improving water quality in catchments with farmers like John Burke. One of many approaches being taken is the Tīmata method, offering farmers a low-cost alternative approach to traditional native plantings. 

Retiring less productive farmland like steep hill areas or erosions prone land back to native bush and forest can positively impact on water quality, greenhouse gas (GHG) emissions, and farm management. Alison has been encouraging this approach with farmers for many years now. She works alongside farmers who are looking for ways to enable sustainable land use, including riparian planting and buffer zones for wetlands and retiring steep hill side areas and erosion prone land. One of the most significant barriers to date has been the cost of native planting.

Alison has been promoting the Tīmata Method, a low-cost native regeneration model. With support from Our Land and Water National Science Challenge, she is working with farmer John Burke and others to create a resource outlining the method for those interested in implementing it. 

John works alongside Alison on some local catchment projects and is affiliated with Tipu Whenua. In discussions they talked about the importance of sharing knowledge with farmers and the wider community and Alison was able to get backing from Our Land and Water to create a video resource and write a white paper on the Tīmata Method.

The fundamental principles of the Method are the use of easily propagated and planted nursery crop species, cultivation of plants in small-size containers and fewer trees planted per hectare than under conventional guidelines. Deployed as a whole, the method lowers costs and makes more efficient use of time and labour.

The method was named by John Burke. In essence, it means ‘kick start’. John was part of the Mānuka Research Partnership, a PGP project that trialed growing mānuka on marginal land to stabilise erosion-prone slopes while growing plantations to supply medical grade mānuka honey. John saw how the mānuka, a native ‘nursery species’, enabled the natural regeneration of ngahere (bush and forest). 

John began trialling this method for retiring land on his farm Pukekauri, in Katikati. The principal at play is plant succession, where each plant community improves the conditions for the next. Mānuka and kānuka kick start the natural regeneration process. They improve the soil and grow the mycorrhizal networks that underpin ngahere (and differ markedly from pasture soil biomes which are predominantly bacterial). These shrubby trees are in turn naturally replaced by secondary colonisers, which can include mahoe, ribbonwood, maire, and mapou, and then the final stages are the growth of longer-lived species such as rimu, totara, matai, and kahikatea.

Alison explains that the process adheres to te ao Māori principals – it is a whole system approach that works with nature, and it takes time – podocarps and conifers will start to assert dominance after around 25 years.

The reduction in cost is achieved by working with nature to plant woody shrubs that will start the natural process using forestry-grade seedlings (as opposed to traditional Planter Bag or PB plants) for more efficient use of labour, and spacing seedlings at around 2,500 stems per hectare.

Forestry-grade seedlings have around 300mls of soil compared to 1-2 litres of soil on a larger PB plant. This enables a forestry planting method to be used, where workers can carry a box of 100 or so seedlings at a time. PB plants are often difficult to get into a site, and to plant on steep land. The plastic waste generated from the bags is a further issue using PB plants.

The Tīmata Method significantly reduces costs. In 2022 establishment in the Bay of Plenty using this method was approximately $2.20 per plant, which covered pre-plant spot spray, plants, and labour. This equates to a cost of $2,811 per ha at 3m spacings and 1,111 plants per ha, or $6,050 per ha at 2m spacings and 2,500 plants per ha. This compares to a conventional large grade/high density cost of $30,222 per ha ($6.80 per plant at 1.5m spacings and 4,444 plants per ha).

Like all plantings, weed and pest management is essential to ensure acceptable survival rates. Weeds are reduced when the canopy closes over – usually within 5-8 years, though Alison has one area on her own farm that closed over within 4 years.  

Once the nursery crop is well established, broadleaf, podocarp and conifer trees can be planted. It is possible that the planting of a well-managed nursery crop will allow natural regeneration without the need for further investment for planting of broadleaf, podocarp, and conifer tree species; particularly if it is adjoining or near an existing native forest, which can provide the seed source for manu (birds) to facilitate dispersal. 

Secondary plantings require a good understanding of the land and local ngahere to identify appropriate species for the area. The entire method is contingent on careful observation of the land and catchment and requires a systems approach. 

“It’s in the landscape where we integrate our response to water pollution, climate change and restoring biodiversity. And it’s the landscape, itself, that tells us how to do this.” John Burke says.

Alison and John are involved in sharing the Tīmata Method with interested parties and both continue to be involved in research to quantify the results and to trial adaptations to the method. Variations to the Tīmata method are being carried out and evaluated in different parts of New Zealand. These include: 

• Planting 100% mānuka and kānuka and allowing time for natural introduction of other native species - considered worthwhile if the site is adjoining existing ngahere
• Planting 100% mānuka and kānuka followed by planting of strategic groves of bird loving coloniser species after 2-3 years
• Incorporating naturally occurring gorse/broom as a nursery crop in conjunction with mānuka and kānuka and other colonisers
• Over-sowing mānuka and kānuka seed
• Higher density forestry grade planting on slow growth and extremely weedy sites
• Totara as a nursery crop in Northland 

There is also work underway at CRI Scion to test plant pot sizes and rates of regeneration.

Alison says, “Repurposing marginal land (including former wetlands) in most cases makes economic sense. There are examples on farms around NZ where such land areas have been repurposed into trees, and the total pastoral farming business profit has shown little change and, in some cases, increased from farming a reduced effective grassed area. Add to this the benefits of carbon income, improvement in farm workability and aesthetics then the investment into ngahere starts to stack up.” 

These notes were in part prepared from the white paper, “Retiring Farmland into Ngahere”, by Alison Dewes, John Burke, Bronwyn Douglas, and Steff Kincheff.

See also:

https://www.tipuwhenua.com/