It's a fine line between scourge and interesting casual isn't it? I have this in South-Western UK and enjoy it - don't know how it arrived but definitely not invasive here. Whereas Muscari armeniacum I just cannot control and will have to say farewell when I move similarly. The moral seems to be that when Liliaceae decide to be weeds they are very intractable. (There are several alliums that I know of gardeners cursing. I have even heard a complaint about Leucojum aestivum being invasive !) (See the lovely Nothoscordum at http://www.floralimages.co.uk/pnothoborbo.htm - it's the same one I think despite newer name.) John Crellin