Broad-leaved dock is a vigorous perennial native to Europe and naturalised across most of North America. It forms a deep taproot and a rosette of large oval leaves, 60 to 150 cm at flowering, and sends up tall stalks of small greenish flowers that ripen to rusty-brown seed clusters in late summer. It is a weed of pastures, gardens and waste ground.
It is persistent because of two things: seed that stays viable in the soil for decades, and a taproot that regrows from any piece left in the ground. Dig the whole root with a fork when the soil is damp, or cut the plant at the crown repeatedly until it gives up; hoeing the top off only makes it bushier. Never let it set seed, and keep it out of the compost unless the heap gets hot.
The leaves have a long folk use for soothing nettle stings, which is why the two so often grow together, and the seed heads feed finches in winter. The small copper butterfly lays its eggs on docks and sorrels. Deer and livestock mostly avoid it, since the leaves are high in oxalic acid.