Was that the Velvet-leaf Mallow (Allowissadula holosericea) seeds, by any chance? I grow some of that one... does spread by seeds. It's a host plant for a couple of skipper butterflies.
I would feel more optimistic about a bright future for man if he spent less time proving that he can outwit Nature and more time tasting her sweetness and respecting her seniority. E. B.White
Integrity can never be taken. It can only be given, and I wasn't going to give it up to these people. Gary Mowad