I have not grown it, but I looked it up and saw that it is in the mint family. Mints are known for their vigorous spreading. The title on the site listed below may give you some indication of what the plant is like. (They call it hedge nettle. I don't think too many people would buy something called hedge nettle.) You might want to try confining it by growing it in a pot buried in the soil, a common method for containing mints in the garden.
Bob

Here is a link that might be useful: Stachys palustris

Thanks for the information, Bob!

Hope that spring will be coming soon,

Dan