Seedlings with cotyledons. Key characteristics: cotyledons lanceolate in shape. First true leaves are alternate.
Vegetative plants. Key characteristics: leaves are alternate and often have purple watermark on their surfaces.
Stem. Key characteristics: a paper-like sheath known as an ocrea is present at the base of the petioles. The ocrea found on Pennsylvania smartweed does not contain hair.
Flowers. Key characteristics: spike-like clusters range in color from white to pink.
Seed. Seed are rounded with a pointed terminal, reddish-brown and approximately 3.0 mm long.
Life cycle: summer annual.