Tall waterhemp (roughfruit amaranth, rough-fruited water-hemp)
A distinguishing characteristic of tall waterhemp that sets it apart from similar members of the genus Amaranthus is the lack of hair on its stems and leaves. This characteristic gives the plant a bright, glossy appearance.
The leaves of tall waterhemp tend to be long and narrow.
The stem is typically erect and slender and can be up to three feet long. The color of the stem is green or red.
Tall waterhemp is a dioecious plant. The seedhead branches in the female are numerous, short, and smooth. The male seedhead branches are fewer, longer, and more slender than those of the female.
The species has terminal spike inflorescences and very short bracts with simple to highly branched flowers. Seed produced is reddish to black and less than 1/32 inch in diameter.