Work to ‘streamline’ efforts to establish native plants on river banks

Efforts to find the most farmer-friendly ways to establish native plants on river banks are continuing with a new approach—establishing pasture grasses first.

The Sherry River Landcare Group in the Tasman district wants to rehabilitate farmland along the river with native plants, removing introduced woody ‘weed’ species such as old man’s beard, crack willow, gorse, broom and blackberry. Native species will maintain bank stability and improve biodiversity, but suppressing weeds so natives can take hold over large areas isn’t easy. Trials using chemical control, weedmats and carpet show chemical control is cheapest. However, this approach requires repeated spray applications and considerable care to avoid unwanted spray damage.

A new trial is just underway on a steep bank 200 metres long and 20 metres wide on Bill and Jeanette Booth’s farm at the junction of the Sherry and Wangapeka rivers. Woody weeds are being cleared and pasture grasses sown, so that a vigorous grass sward can suppress a new crop of weeds. In a year, the grass will be sprayed and natives planted (with minimal soil disturbance) into a dead grass thatch, and the dead grass will suppress weed establishment for sufficient time to get the natives established.

If this method is successful, it will be repeated annually along the river on the Booth’s land. It is hoped that other farmers will take it up.

Funded by Landcare Research’s ICM research programme, ENSIS Senior Scientist Nick Ledgard and NZ Landcare Trust regional coordinator Barbara Stuart are involved in the restoration trials, along with various landowners of the Sherry River catchment.

Nick Ledgard says the major point of these trials is to find the most farmer-friendly means for land owners to establish native plants successfully.

‘Farmers want the simplest, most cost-effective and time-effective ways to streamline this process. If we sow pasture grass, then kill it and plant amongst it, you have very little soil exposed, so the opportunities for new weeds are reduced.

‘We don’t believe the traditional methods using chemical control are the best techniques for larger scale riparian planting – and using mulches such as carpet and weedmats are too expensive and time consuming.’

NZ Landcare Trust Upper South Island Regional Coordinator Barbara Stuart says if it works, the pasture method would show promise in promoting native establishment over large areas.

‘Landowners would be more likely to take it up, as it would not be cost- or labour-intensive.

‘As farmers familiar with pasture establishment practices, they certainly have the skills to do it.’

Meanwhile, Bill Booth says he’s pleased to take part in the project.

‘I’m very interested in getting natives alongside the river. The river is used by many people, and natives are so much better than the rubbish that’s been growing there, particularly old man’s beard, gorse and broom.

‘It’s only a small area for a start. It’s now a matter of seeing what happens.’

ENDS

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