I've heard tisane used, yeah, but then I hang around with francophones.

And - huh. Lemon balm in the bath, you say? Dried or fresh? and how much would large quantities be, do you suppose? I mean, by mid-summer I'll be able to fill the whole frigging tub with fresh lemon balm leaves, and it's quite a big tub too. But I suppose you'd have to leave some room for the water ...