Some Ornithogalum are indeed invasive, like O.umbellatum and arabicum, but this is due to the excessively fertile soil. In habitat O.umbellatum isn't at all invasive and it grows usually in small clumps or lonely. O.arabicum also proliferates with an abnormal number of bulbils, which make a clump of leaves with no flowers in the following years and thus it needs to be digged and clean from all offsets and replant only the biggest bulbs. But other species like O.montanum and O.comosum are non offsetting even in cultivation and are worth to pot culture Angelo Porcelli Italy