There's no doubt that Oxalis pes-caprae has conquered much of the world and developed the hatred of many people. But, I will assume the stance of protection for its double form. Here it is in bloom today (http://www.flickr.com/photos/andrewrmw/). This clump of specimens has been there for over ten years, probably longer. It does not set seed and the bulbs do not spread. It gets absolutely no care, blooms after rain, and quietly dies back about two months from now. This plac is paradise heaven for oxalis if they want to go crazy but this one does not. Andrew San Diego