Rumex altissimus

About

Rumex altissimus, the pale dock, is a widespread species of flowering plant in the family Polygonaceae, native to southern Ontario, the United States east of the Rockies, and northern Mexico. A perennial of rich wet to mesic soils, and reaching 4 ft (1.2 m) with yellowish-green to green flowers, it is wind-pollinated.

Summary from Wikipedia