Green smartweed: An annual herb. The green leaf blades are alternate, narrowly lance-shaped, mostly 3-15 cm long. Green stems are erect or trailing, up to 1 m tall. Many root at nodes. Hairless to slightly hairy. The flowers are crowded into terminal, cylindrical spikes. Each individual flower is 5 petalled, to 3.5 mm long and pale. The seeds are 2 mm long, nearly black, smooth, shiny, and 3 sided. Spreads rapidly by seed.