Plant id needed. A perennial that came from a friend, it is colonizing a section of the garden.?

It is NOT A MINT or VERBENA or erfly Bush. No info about flowers yet, sorry. Stems: square, smooth, reddish, not woody. Leaves: smooth and thin, not fragrant, slightly heart shaped oblong, 1.5 to 2.5 inches long, 1.25 wide, opposite, entire, pinnately veined, petioles have coarse hairs (or hairy stipules?) along the edges. It is about 1.5 feet tall now, each plant one very straight handsome stem, growing in full sun and rich soil, in Southern Vermont. It think it is drought tolerant.