common yellow woodsorrel (oxalis stricta) in bloom : (pix sanjiv shukla)

oxalis stricta common yellow woodsorrel family oxalidaceae upright yellow-sorrel lemon clover sourgrass sheep weed pickle plant herbaceous flower north america eurasia introduced woodland meadow perennial annual erect decumbent lies branches garden fields lawns sun shade alternate leaves divided three heart-shaped leaflet curl night open day photosynthesis seed capsule disperse green foliage