The leaves remind me of nettles! They have square stems too and I think most of them sting when touching the hairs.
Could belong to Verbenaceae. Lantana montevidensis has similar shaped leaves and spreads.
http://www.bio.utexas.edu/cour...
Would you believe there is a Lantana urticoides, no wonder the leaves remind me of nettles!
http://museum2.utep.edu/chih/g...
http://www.bio.utexas.edu/cour...
Plants in Verbenaceae ...
http://botany.csdl.tamu.edu/FL...
I guess the test now is to see the flowers.
