A closeup of pale smartweed (Polygonum lapathifolium). The round stems are hairless and somewhat swollen near the base of the leaves. The alternate leaves are up to 8" long and 2" across. At the base of each petiole of the leaves, there is a membranous sheath (ocrea) that wraps around the stem. This sheath often has longitudinal ribs, but lacks bristles along its upper margin. With age, the sheath gradually turns brown and peels away.