Regenerating with seeds, not seedlings
Mimicking nature might be a better way to breathe new life into New Zealand’s native forests. Will Harvie reports.
After the earthquakes, Andrew Cummins was contracted to revegetate parts of the Port Hills red zone with native plants. On the sites, he found lots of clay and backfill. He had about 20 years experience in native regeneration in New Zealand at that point and knew this was unpromising soil for native seedlings.
Seedlings are typically one to three years old and come in little containers rich with soil and compost, but survival is often mixed.
So he decided to experiment by planting seeds, which is how nature operates.
To make germination more likely, he added a rich infusion of compost.
On the first 100m² trial site, it worked. The next year, he planted seeds over 1000m² and that worked too. The next year, he tackled 10,000m² or 1 hectare and that worked too.
He was finding a 60% increase in surviving plant stems compared to planting seedlings 1.5 metres apart, the usual approach.
He called the innovation an “Enviroblanket”, not because a woven cloth was included but because he was putting down a rich and comfortable blanket of soil and nutrients that was excellent for seed germination. “The concept was to reproduce as best we could the environment of a forest floor. And to me, that means it's rich in leaf litter and organic matter and it's holding moisture,” he said.
His company, Red Tree Environmental Solutions, has been innovating the idea ever since. They’ve found it works well in coastal areas, along the edges of waterways, and in wetlands – places with good moisture.
They’ve also been innovating how seeds can be spread. In early trials, seeds were spread with pressurised air.
In 2020, on a 6ha block downstream from the Christchurch Adventure Park, Red Tree spread seed through a constructed wetland with farm machinery.
For hard-to-reach and dangerous sites, Red Tree has a drone that can precisely drop seed pellets about the size of a marble. In the right circumstances it can also cover a hectare in 10 minutes.
Red Tree initially thought the Enviroblanket was a product, but they’ve since realised it’s a process, said David Rothe, the company’s ecological engineer and drone pilot.
Every job is bespoke, said Cummins. They investigate the site, come up with a seed and nutrient recipe, plant the place, and go back to check the results. “This is an ongoing experiment,” he said.
But it could become more of a formula. One goal, for example, is to help farmers regenerate native bush on retired land. At the moment, planting a hectare with native seedlings might cost $30,000 to $40,000, which is too expensive for many farmers.
“If we can crack direct seeding and reduce the inputs, then we can bring down the price and there would be a much greater uptake,” Cummins said.
The concept is being trialled with the Greater Wellington Regional Council, which is retiring swathes of pasture it owns and replanting natives in its Recloaking Papatūānuku project.
The project allocated Red Tree an 8.5ha block of land for seeds, which is now the company’s “leading edge” site for regenerating former farmland, Cummins said.
“This experiment of ours is based in biomimicry,” he said. “How does the forest grow? How does the forest regenerate? ... What conditions do they need to germinate and how do we repeat that? Nature leads and we follow.”