I thought I'd ask some experts before poisoning the eastern United States with this. I bought a pot of Allium atropurpureum a few months back as it had an unusual (for me) dark purple, nearly black, flower head. It has just finished with producing some seed. I was away for about two weeks, and on return noticed that one of the flower stalks was down. Closer inspection revealed about 17 bazillion (a technical term often used in estimating oil well leakage) little bulblets. Clearly this plant is going to move around a bit. The question for the alliophiles---how badly invasive is this plant? Shall I get it out of the garden fast, or does it remain more or less in one place with just occasional escapees? Thanks. Steve Putman in scorching Delaware