A popular park shrub in the past, the rugosa rose (Rosa rugosa) has since become a nuisance in natural habitats due to the fact that it thrives on sandy and rocky shores, displacing native shore flora.
The spread of the rugosa rose is combatted by various means, as with other invasive alien species. One method that has proven effective against rugosa roses is the removal of new shoots from the rose bushes by hand. As long as this is done repeatedly, the plant eventually withers, dying where it stands. In Kallahdenniemi, the spread of rugosa roses has been successfully stopped using this method, and the same method is now being used on the rugosa roses of Vallisaari island as well.
There are also naturally occurring roses growing on Vallisaari island, namely glaucous dog roses (Rosa dumalis) and soft downy roses (Rosa mollis). You can tell these apart from rugosa roses by their sparser thorns, which are curved on glaucous dog roses and straight on soft downy roses.