Lupines are beautiful but at the same time a threat to the wildflowers that naturally exist in our environment.
At Älglunds power plant near Bygdsiljum, Skellefteå Kraft is conducting a trial to determine the most effective method of removing the plant. Lupines have spread rapidly in the area around the power plant.
– Invasive species are one of the biggest threats to biodiversity. If lupines spread, they're a significant threat.
And if the area's native wildflowers are outcompeted, butterflies and other pollinators will also disappear.
– We want to learn how to deal with the problem. Lupines are also a topical issue, as the Swedish Environmental Protection Agency (Naturvårdsverket) sent a letter to the government this spring proposing that lupines should be managed in the same way as other species on the EU's list of invasive species," he says.
If that happens, landowners could be legally required to remove the lupines.
– We want to be proactive, but there are no well-established methods yet. I'm concerned about how big the problem will become in ten, twenty years if we don't do something, says Rocksén.
"Here, it was species-rich four years ago when we surveyed. Now it's full of lupines," says David Rocksén.
We stand in a field that more closely resembles a lupine plantation.
Around us, we hear popping sounds.
– It's the lupines releasing their seeds, Rocksén informs us.
He digs up a large root.
– Digging out lupines is very labor-intensive, he says.
"The roots are robust and can reach deep. They tolerate drought well," says David Rocksén.
That's why Skellefteå Kraft is now testing multiple methods.
They've marked large squares where the lupines grow and treated them in different ways to weaken them.
The test area covers about half a hectare. This specific area, where the lupines have produced seed capsules, will be covered with weed fabric and peat in the fall, sown with meadow seeds.
A bit further away, they've cleared lupines from two large squares, removing the remains from one. In one square, they've applied lime to the plant's roots. In another, they're testing ash, and in a third, salt.
David Rocksén applies large salt tablets that are intended to dissolve into the lupine roots and kill them.
The results are striking. There's a significant difference in lupine growth between the various squares.
In the two where they were cleared, there are plenty of leaves and even some flowers.
To the left, ash has been applied to the roots. To the right, the lupines have been cut and raked away earlier this summer. The ash seems to be more effective.
In the squares treated with ash and lime, the lupines are noticeably disrupted by the treatment. Half of them have disappeared. The remaining ones are smaller, with fewer flowers.
–The salt has had the best effect. I wouldn't have expected that, notes Ulf Stenmark, who works together with Rocksén in the area.
Out of 100 lupines, eight remain. The downside is that salt also kills many other plants growing there.
Lupines have the ability to bind nitrogen. They store their energy in the root and grow up quickly in the spring. That's why they're testing applying lime and ash to the plants.
– We want to make sure the root doesn't thrive.
Lime is piled over the lupine plant roots. "Biodiversity is a priority in Skellefteå Kraft's strategy," says David Rocksén.
They spread salt, lime, and ash earlier this year and also now when the lupines have bloomed and used up much of their energy.
Rocksén mentions that it's possible to test lime and ash at home in the garden if you have lupine problems.
– Let them bloom, pull them out at the ground, and then cover the root with a pile of lime or ash." He adds:
– But I want to emphasize that we're testing methods here. It will take a few years of testing to know what has the best effect.
That's why they will return to the site next summer to evaluate the eradication efforts.
– I guess we won't get rid of everything. This is a long-term effort, and we need to tackle the problem before it gets too big, he says.