Thanks for the help in advance! This is spreading and I'm not sure if if I should start yanking it out.
Sorry, I don't know what it is, hopefully someone else will have the answer. In situations when I don't know what I am dealing with I usually wait for the flowers to help me decide what to do. Hopefully it will not spread much more now, plants usually do that mostly in spring.
Those leaves aren't all that distinctive. Are the stems square? It doesn't look too different from Prunella vulgaris. Are the leaves fragrant? Of course, if you don't want it, you'd rather rip it out now and plant something else, but the ID is really in the flowers.
