Trim it back if you like. I generally let mine be. It should keep most of it's leaves through the winter (Zone 5) at least that's my experience.
I'll clean anything up in the spring that I don't like from its winter experience.
If you want a more trimmed formal appearance, then the answer will be different. I let mine grow as it will as a ground cover. I have three different thyme varieties I let compete there. Works out well for me.
Phil |