Procumbent yellow sorrel

Unfortunately I´m allergic to tripods, which makes macros difficult for me. This is a "procumbent yellow sorrel", which a) is very small (extra 1 shows the size), and b) disappears when it´s not in direct sunlight. Literally, it folds into itself and its yellow petals can´t be seen. It has appeared uninvited (presumably wind-borne or bird-borne)  in some local flower pots. "Procumbent" in this context means it crawls on its belly, and it has no roots. 
I´ll put a couple more photos, which show the symptoms of my tripod allergy but which may be interesting, in extras. It´s for Wildflower week.