Polygonum patulum

Polygonum patulum, called tree hogweed, is a species of flowering plant in the knotweed family. It is native to the Mediterranean region, eastern Europe, the Caucasus, Siberia, Central Asia, Mongolia, and the Province of Xinjiang in northwestern China. It has also become sparingly naturalized in scattered locations in Australia and North America.

Description
Polygonum patulum is an erect or semi-erect annual herb up to 80 cm tall. Leaves are green or blue-green, up to 5 cm long. Flowers are green, pink, or white.