Flower:

Densely packed, nodding spike-like racemes, typically 2 to 4 inches long (or longer!) and about ½ inch in diameter, mostly at the tips of stems, sometimes in upper leaf axils of branches. Flowers are greenish white to pink, 1/8 long with 4 or 5 tepals (petals and similar sepals) that barely open, and nearly stalkless. The stalk of the raceme can be smooth or covered in glandular hairs.

Leaves and stems:

Leaves are alternate, lance-like, up to 8 inches long and to 2 inches wide, widest near the base with a rounded taper to the short stalk, and a long, even taper to a sharp tip. Sometimes there is a dark blotch on the upper surface but usually not, the stalk up to 5/8 inch long. Edges are toothless but have short, cilia-like hairs. Surfaces have inconspicuous translucent pits (punctate), are smooth or with matted, woolly hairs especially underneath or along the main veins, particularly when young.

At the base of the leaf stalk is a membranous sheath (ocrea) that extends up around the stem and is typically prominently ribbed, its upper edge smooth (no bristles or fringe) or torn, becoming dark rusty brown and peeling with age. Stems are erect to spreading, densely branched, glossy smooth, green or often red and swollen just above the leaf axils.

Fruit:

Fruit is a smooth, dry seed about 1/8 inch long, brown to black, shiny or dull, usually disc shaped.

Notes:

Nodding Smartweed, formerly known as Polygonum lapathifolium, is native to both the eastern and western hemispheres and in North America a mix of both native and non-native ecotypes is likely present. In Minnesota it is arguably the largest of the smartweeds and can most easily be distinguished from other Smartweeds by its long, drooping flower clusters. A somewhat weedy species, it's common throughout the state, quickly filling in receding water lines of shallow marsh areas, disturbed road ditches, urban retention ponds and rural flood basins.