I have had good success with overwintering seedlings in pots. I have a spruce tree in my yard and I take all of the pots, lay them on their side under the spruce tree, and take a bag of mulch and completely cover them. Out of about 7 pots, I only lost one. I usually do this in late October or early November, depending on the weather. I like to wait till it at least gets consistently cold. Don't want them covered up if the temps get too warm.
