Flower:

There are separate male and female flowers on the same plant. The female flowers are green with 4 sepals of unequal size and look more like tiny curly leaves with feathery edges than flowers. They are in erect or flat branching clusters at the top of the plant.

The male flowers are in loose branching clusters that arise from the leaf axils starting about midway up the plant. Individual flowers are less than 1/8 inch across, white to greenish with 5 tiny petals.

Leaves and stem:

Leaves are oval to egg-shaped, to 6 inches long and 4 inches wide, with serrated edges, a sharply pointed tip and a long leaf stem. Attachment is alternate. The leaf stem and main stem are both covered in stinging hairs. The leaves may also have stinging hairs.

Fruit:

Fruit is a dark, round, dry seed

Notes:

This can be a painful plant, though the stinging doesn't last long. Wood Nettle is not to be confused with Stinging Nettle, which has narrower leaves oppositely attached. False Nettle is another similar species, but it is hairless, its flower clusters are unbranched, and its leaves are also opposite.