I'm really confused by what looks like an easy-to-identify plant. This is a volunteer that has been freely reseeding itself within the span of one season.

At first I thought it might be perilla (shiso,) but the flowers and stems don't look right at all. Also it's not at all aromatic (other than generically herbaceous) like perilla.

It's starting to look more like some variety of nettle to me. BUT here's what has me really confused: It doesn't sting. At all. And the only non-stinging nettles I've found online look nothing like it.

Leaves are hairy on both sides, moreso on the bottom. Stems have five lobes. Flower clusters are branched, not a single spire. Leaves have a very mild flavor, not unpleasant or bitter (yes, I chewed on bit.)

West Indian Wood Nettle (Laportea aestuans) ?

Janine, Laportea aestuans was one of my first guesses too, and it looks very similar. But all the literature seems to indicate it has stinging hairs.

My plant has hairs, but no sting.