Uh, it's not hardy where you are, as far as I know. You'd want to dig it up and put it in a pot so that you can overwinter it inside.... if you'd like to do that.

Maybe you can give it a good trim and dry it for cooking, then wait until it is a bit colder for transplanting. We have clayish soil here in Chicago, and it took me a while to get thyme set to grow and survive winters -I am in zone 4-5. Plants seem to like rocks or cement nearby, or other small hardy bushes to hide when it is cold. I'd say move or divide next spring if you can. That way it will have time to grow good roots before winter comes.

It actually is hardy here. I dug it up at our last residence where it was growing wild to bring some with us when we moved...but that was in the spring. I've already dried some, but I suppose I can dry some more. I don't have enough light inside to overwinter it, it gets leggy and tasteless, so I guess I'll wait until next spring and move some of it to another area. Thanks for the suggestions!

Is it an upright type? Thymus vulgaris is hardy to zone 5 and Thymus x citriodora the same. Can't imagine which thyme you could have unless you were seeing self-sown plants at the old place. They can grow quicky in one season if their happy enough.
You say it's spreading; so do you mean it's creeping or the clump is getting larger? You can cut it back hard; Thyme is actually one of those that does perform best with frequent good prunings. I do so with both creeping and uprights types.
I have had success moving my T. vulgaris 'German Winter' and Citrus Thyme in both fall and spring. My 4 year old cusiony clumps grow to about 15" wide with a good hard pruning in early spring to prevent that unsightly woody center and about 1/3 of the plants are removed in summer for use. When I have moved them in fall I also pruned them back pretty hard again.

Vera

Vera, what I meant by 'growing wild' is that it was growing in several places out in the middle of a field...it wasn't in a garden area or near the house. I assume it was in a garden at some point, but it had naturalized out in an open area. We used to rent an old farmhouse and the first summer we were there, from the kitchen window, I could see patches of purple off in the distance. Upon further investigation, I found it to be mounds of thyme...common thyme I'm guessing, it's not lemon thyme. This property is in zone 3 in NW Wisconsin and the thyme is that hardy. We live closer to zone 4 now, about 40 miles south of the farmhouse, but it still gets well below freezing here(about 20 below last winter) and the clump I transplanted into a raised bed came right back this spring. It is about 20" in diameter, not really out of hand, but I planted some other things too close and I just wanted to move some of it to another part of the yard...spread the love, so to speak :)

Hi, I also have it growing in my field that I mow every week in zone 5 NYS. It's funny I found your question because I just transplanted some yesterday. Hopefully it will take ok. It's smells nice when I mow. I wifi get a picture also