My neighbour has Lesser Celandine (ranunculus family) growing in her grass boulevard in Vancouver. For 3 years she has been trying to dig it out to no avail and now it has spread to areas not adjacent to hers. She has tried covering some with thick cardboard to prevent photosynthesis but the tiny bulbils wait and take off again when they do have light. I've heard that disturbing the soil can make it worse and the bulbils can be washed down the street with heavy rainfall. She does not irrigate this area. Anyone been successful eradicating it by whatever means? In Vancouver we are restricted with certain herbicides.