A species is defined as alien to an area if its presence is a result of human transportation, both intentional and unintentional, and when it has not previously occurred in that space. Alien species can apply to both plants and animals, but in the park areas at the university we mainly focus on the plants.
Many alien species have been assessed by Artsdatabanken as harmless and can contribute positively to enhancing biodiversity by creating habitats and green corridors to support pollinating insects.
However, certain plants are deemed undesirable, meaning they are prohibited from being planted, or subject to application prior to any potential planting. Some are also classified as “very high risk”, “high risk” or “potential high risk”, depending on where they are planted. These are referred to as invasive species.
The University of Oslo has its own team of trained gardeners, and Park Services has a comprehensive overview and strong routines in place to combat unwanted alien species on the university’s properties. This includes systematic removal of Canadian goldenrod, Russian knapweed and sow thistle. Currently, there are no recorded observations of Japanese knotweed, Persian hogweed, or other undesirable invasive species on the grounds.
A significant portion of the properties owned by the university falls under protective regulations. This means we are responsible for preventing the existing vegetation that was present when the areas were designated as protected. Any proposed replacement of plants in these areas requires approval from heritage authorities. The Park Services team regularly evaluates the necessity and feasibility of replacing older specimens of less desirable or unwanted species.
All vegetation on the grounds undergoes risk assessment in accordance with relevant laws and regulations, and a high standard of maintenance is upheld. This reduces the risk of spreading to vulnerable areas. When planning new plant beds or landscaping projects, we strive to avoid using plants that are categorised as a risk.
Keeping an alien at check at Blindern
In the raised flower beds between the Faculty of Humanities and the Faculty of Social Sciences, you can find Alchemilla mollis, commonly known as lady's mantle, growing under the cherry trees. This perennial was introduced to Norway as an ornamental species relatively recently and is by definition considered alien.
Alchemilla mollis is primarily characterised by its soft, blue-green leaves that are shaped like hands, collecting water droplets like glass beads. During early summer, it produces a decorative display of small yellow-green flower clusters. It provides excellent ground cover, forming dense mats, and has many desirable qualities as a garden and landscaping plant.
However, a potential drawback is that it can spread very quickly in certain areas, consequently outcompeting other native species. Fortunately, planted in raised beds such as in our parks, the lady’s mantle poses no threat to other vegetation. Furthermore, the flower clusters are cut back to prevent seed formation.