'Stay calm and keep planting' environmentalists urge

Friday, 2 September 2022

Meg Harry from the FuturEcology team pulling flood debris out of plants by the Wakapuaka.

When it comes to planting to mitigate flooding and slips, any planting is good planting, says a Nelson ecology and conservation company.

There aren’t any silver bullets that can stop slippage altogether, but there are little things we can do to reduce the effects, says Robert Fryer, managing director of FuturEcology.

“Anywhere where there's water, even if it is on a slope, grasses like Carex secta have got just such a good net and root system they really hold the soil together.”

Robert says as a general rule, places that were well planted and well established didn't quite get hammered as hard as those that weren’t.

Slips in Nelson are on the move and show how wet the hillslide is.

* Digger used to anchor boulder as man pinned beneath it on a slope

* Police prevent evacuated Nelson house being burgled for a third time

Robert Fryer with native plants and EmGuard bio-degradable plant guards at the Wakapuaka River, Nelson.

“Any planting is good planting to be honest,” he says, though the company prefers natives for their biodiversity values, which exotics may not have – worse yet, they may end up as weeds.

“Kānuka is always a go-to for us on slopes, or ake ake. They get away quickly, hold the soil together and keep the rain off,” he says.

These are primary species – those that get planted out in the open before tōtara and other statue trees are added in.

Close to streams, they use pukio because of their net root systems holding the soil together but also because they don’t impede floodwater flows.

Stepping back from the river, they use larger species such as toetoe, flax “if it’s wet and puggy and spongy” along with trees such as the lowland ribbonwood along with native lacebark.

Native Carex secta and Phormium cookianum thrive in wet areas. (file photo)

“The beauty of these things is that they flop over in a flood and then they'll either stand up or grow from the crown. They've evolved alongside of rivers so they’re supposed to be there.”

Kōwhai copes with being very dry, and also with the wet, provides good shade and biodiversity values.

“It’s a very versatile species we don’t use enough of”.

Now 58, Robert says all he wants to do now is plant trees: “I’m happy if that’s all I do.”

Robert and his wife Jan and a wider team of workers and volunteers have planted 30,000 plants on the banks of the Wakapuaka River in the Cable Bay Rd area as part of the Wakapuaka Mauri project.

Jan says the “bulk” of these have survived, despite being covered by three metres of water when the river was running at 200 times its normal flow.

Some sections that didn’t were where the river totally washed the banks away.

Where there are slips or steep banks, they “plug in” silver tussock - it’s remarkable what that will hold, she says.

Flax is a good plant for riparian plantings and generally holds up well in flooding.

If plants do end up getting washed away, the most important thing you can do is plant again, Jan says, using the planting window available.

“The message to get to people is ‘Don’t despair. Stay calm. Keep planting.’

“We’ve still got a month of good planting time.”

Titoki Nursery managing director Tim Le Gros said the best local native plants for root holding capacity were tutu, karamū and cabbage trees.

For coastal hills other species include ake ake, kanuka, koromiko, tauhinu, ngaio, akiraho and flax, he said, many of which the nursery still had available.

For wet areas nearer rivers, he recommended Carex secta or Carex virgata, harakeke (flax), and toetoe were good options as they flopped over and allowed water to flow over them carrying most of the debris, and then stood back up.

“Cabbage trees are again useful as being single stemmed rather than branched shouldn’t catch as much of the debris being carried down the river.”