[9] 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.

The species has terminal spike inflorescences and very short bracts with simple to highly branched flowers.

[12] Tall waterhemp predominantly grows in wet habitats, such as ponds, marshes, lakes, creeks, and other riparian zones.

Germination occurs typically after soil temperature alternation, as this is required to break seed dormancy.

[16] While tall waterhemp cannot self-pollinate, due to having separate male and female plants, it does not require any vectors for pollination.

[20] In North America, tall waterhemp is considered a major weed of agricultural fields and other disturbed habitats.

[11] Because of the long germination window for tall waterhemp, a single herbicide application is unlikely to be an effective control strategy.

[8][15] Even more alarming is the emergence of waterhemp resistant to the latest generation of herbicides, HPPD inhibitors.

[25][23] According to Bob Hartzler of Iowa State University, the most effective control of tall waterhemp is achieved by cultural practices that promote growth of the desired vegetation.