Broadleaf dock (Rumex obtusifolius) is a related weed that can also grow to be as much as 4 feet tall. It is easy to tell the two apart: True to its name, the broadleaf type has bottom, or "basal" leaves that are very wide (4 inches across, versus 1 inch across for yellow dock plants). Curly dock has basal leaves shaped like swords, the basal leaves of its broadleaf dock are shaped more like shields.