Ongoing research on new methods to control garden lupin
This text was published in the blog of Priodiversity LIFE. Check out the other blog posts as well (metsa.fi).
19.6.2025
New methods are needed to manage invasive alien species. In the project Priodiversity LIFE, Natural Resources Institute Finland is doing research on how garden lupin could be hold off effectively and environmentally friendly.
Within multiyear field experiment, we examine the effectiveness of two methods: the traditional way, i.e. cutting, its timing and repetitions, and the novel biodegradable mulch. The field experiment started last year, and they are conducted at four locations in Kanta-Häme region.
The new kind of mulch is made of mixture of tar-like pyrolysis liquid and the zero-fiber pulp, which comes as a by-product from pulp mills. When the mulch dries, it hardens and prevents lupines developing into seedlings. Over time, the mulch degrades and original vegetation are hoped to get more living space. As the mulch is biodegradable, it leaves no plastic in nature and using the zero-fiber serves circular economy. The pyrolysis liquid mulch has been tested earlier in preventing Giant hogweed. Tentative results on the efficacy of the mulch are possible to get already at the end of 2025.
Garden lupine is invading new areas fast
Garden lupine is classified as a harmful invasive alien species, which threatens biodiversity in Finland. The species was brought from North America to Europe to decorate gardens and yards 200 years ago. However, garden lupine turned out to be invasive, and first sightings of escaped lupine are from the end of 19th century already. People continued to seed this beautiful-blooming species into home yards and summer places, from which it has escaped particularly to roadsides. As of now, garden lupine is found almost throughout Finland, except for northernmost Lapland. Especially during this century, lupine has spread at an accelerating pace. Seeds move easily from one location to another with soil transportation, vegetation disposals and along with vehicles and machines, such as mowers.
Even though roadsides and railbanks have become especially preferable habitat for garden lupine, it survives at many kinds of growth sites, from wastelands and fields to meadows and esker forests. Garden lupine benefits from its ability to survive well in dry and low-nutrient habitats, since like other legumes, it has symbiotic nitrogen-fixing bacteria in its root nodules. While binding nitrogen from the air, lupines eutrophicate their growth site though, which leads to changes in plant species at the place, and meadow plants who earlier lived by roadside, withdraw from the way of strong-growing species.
Garden lupine is a prominent threat for several species and habitats included in the Red List. Due to this, more efficient methods are needed to prevent the harm of lupine and its spreading, and we wish to produce those in Priodiversity LIFE. An eight-year (2024-2031) project offers a unique chance to follow the recovery of original vegetation after controlling garden lupine, as well as estimating how its prevention will impact on vegetation species’ biodiversity.
Miia Jauni, researcher, Natural Resources Institute Finland
Pentti Ruuttunen, researcher, Natural Resources Institute Finland
Terho Hyvönen, research professor, Natural Resources Institute Finland
Priodiversity LIFE offers solutions to halt nature loss. The project gathers a wide range of committed operators who together have the chance to find the most impactful and cost-efficient ways to stop nature loss in Finland. In the project we will create requirements to make halting the nature loss into a new skill for Finnish entrepreneurs, and to make Finland an expert on international scale. Priodiversity LIFE is coordinated by Metsähallitus Parks and Wildlife Finland.
Priodiversity LIFE – for halting biodiversity loss (metsa.fi)
