The plant species selected were the Italian plumeless thistle (Carduus pycnocephalus, 30% inhibition), the Chinese peony (Paeonia lactiflora, 8-53%), the European aspen (Populus tremula, 25%), the sweet cherry (Prunus avium, 20%), goat willow (Salix caprea, 30%), English oak (Quercus pedunculata, 25%) and Sikkim rhubarb (Rheum nobile, 25%) (Table 1).