every time it rains I get a gazillion of this all over the place. fortunately, it is easy to pull. Its delicate bloom clusters remind me of allysum.
Name of this thug, pls
We get them up here, also. I think they come w/o rain. I have at least a 4' x 8' bed for my cannas & they made an almost solid carpet of groundcover green. I call it a WEED! lol
It looks like something in the Euphorbia family, but I can't tell you which one.
I agree with Josephine - Euphorbia. The Euphorbias are taking off here - Prairie tea, Toothed spurge, and Roundleaf spurge are the problems on my lot. Your's looks a bit different than all these, but here are links for comparison.
http://davesgarden.com/pf/showimage/127165/
http://www.sbs.utexas.edu/bio406d/images/pics/eup/euphorbia_dentata.htm
http://dallas.tamu.edu/weeds/desc/roundleafspurge.html
And you have mighty pretty nails for a gardener.