Buttercup (Ranunculus sp. possibly R. repens)
One of a large genus of about 500 species of flowering plants in the family Ranunculaceae. Most probably the creeping buttercup Ranunculus repens, which has extremely tough and tenacious roots. Buttercups usually flower in the spring, but flowers may be found throughout the summer, especially where the plants are growing as opportunistic colonizers, as in the case of garden weeds.