Sometimes called red nettle, purple nettle, and even purple archangel, it is thought that this is called dead nettle because its leaves resemble stinging nettle (Urtica dioica), though they do not have the stinging characteristic of Urtica. Wood Nettle and White Snakeroot have flowers at the top of the plant, Stinging Nettle and Clearweed have flowers along the sides. Two are the Pilea pumila and a new weed, the Fatoua villosa.” I looked both of these up on the web, and Pilea pumila looks more like what I saw than Fatoua villosa does. In your Stinging Nettle article above you write: “There are some look-alike plants to the beginner. Since both stinging nettle and wood nettle look so much alike — and both protect themselves with stinging hairs — how can we tell these two plants apart?
Leaves are about 2-5 inches long with jagged edges, found in opposing pairs along the upper half of the stalk. Their is one difference: the hairs on the leaves are on both top and bottom. You could argue that White Snakeroot doesn't belong in this discussion because its flowers are clearly different (they actually look like flowers).
Stinging nettle will grow in dense clusters, and stalks can reach 5-8 feet at maturity. It has the look of stinging nettle, with leaves growing opposite each other on the stalk, the fine prickly hairs on the leaves and the stalk, and the rigid leave edges. It also stings when touched. Purple dead nettle is in the mint family, and is called “dead nettle” (or sometimes “deadnettle”) because of its apparent resemblance to stinging nettle, minus the sting.
The most obvious difference is the orientation of the leaves along the stems. Leaves are about 2-5 inches long with jagged edges, found in opposing pairs along the upper half of the stalk. Stinging nettle’s leaves are opposite each other. Spotted nettle (Lamium maculatum) is closely related, however its leaves have whitish spots or blotches. This confuses me somewhat, because I don’t think it really looks like true nettles at all, but to each their own.