These are very tiny flowers and hard to photograph. I really need to bring some home to put under the microscope. They are annuals growing only from seeds and bloom very late in the season. They are not native but come from Europe. I am almost certain that I saw them in Tuscany, Italy when I was there a few years ago and, I think, near the Venice airport too.
Saturday, December 6
I brought home part of this plant yesterday and found that I had misidentified it as Petty Spurge (Euphorbia peplus). It is really a Sun Spurge (Euphorbia helioscopia). It appears that I need to do a lot of record changing in my data base. Sigh! The previous comments are still true except I now do not know which spurge I saw in Tuscany, at the Venice airport, and here in southern Ontario. The genus, Euphorbia, is correct but the species name is in question.