Sheep sorrel

yep. it is somewhat edible, although sour. It works well in a mixed spring salad, with bitter dandelion, tangy grape shoots, and mild corn salad.

PS.it is a strong indicator of acid soil.

Aha, thank you both. Makes sense where it was growing originally in a valley (also just read it likes moist areas) with probably naturally acidic soil. Of course located right near its natural spot is my bed of brambles and strawberries which also tend to like acidity and moisture so this weed has taken it over quite a bit. Now of course, the question is how easily is it controllable. If it is any less aggressive than the growing acreage of bermuda grass and bind weed that I got going, I'd be happy.