thorny weed - buckwheat?
When I found this plant, it reminded me of buckwheat (polygonum sp.), but I haven't figured out what exactly it is. It has more neatly triangular leaves than P. convolvulus, and small but sharp thorns all along the stems and leaf veins. Smaller leaves clasp the stem at each node. Should be easy to identify for those who know it ;-)
Thanks in advance,