Rosemary is notorious for hating being inside. I never encourage people to attempt overwintering. Citrus are very amenable to indoor conditions.

Would you not try a hotriclutre fleece instead this is what I am doing and mulch for as the mulch rots will give off heat bubble wrap the pot and put it in a bucket of leaves again for the heat of rotting leaves rises then I will fleece during the night and allow to breath during the day

I should have added the zone 5-6. It won't survive here without coming indoors.
I was hoping there was a trick. I don't mind buying a new 4" potted plant each year. But for some reason splurged on a tree, which would be a shame to throw out.

I keep mine under lights and keep it well watered (but also make sure the pot drains well). Underwatering has been the main cause of death for our rosemary over the years. One have one now that's a few years old and getting quite large.

You might want to take a few cuttings and do some starts indoors thru your winter months. I know they do not grow much the first year but if you should lose your mother plant at least you will have some starts for later. The little cuttings have never given me a problem during our winter months by staying indoors.

In Atlanta GA, winter lows can go down to 15F and rosemary overwinters, no problem. So does here in Seattle, WA. It grows as shrub in a lot of places. So I have never needed to plant one.
I use it in potpourri, throw some sprigs under the sink cabinet as air freshener.

margowicz - you do not need any of that palaver in the British Isles unless you live in the Highlands of Scotland or the top of a mountain somewhere. Rosemary is hardy pretty much everywhere here and wrapping it up is likely to do more harm than good. The only reason to wrap the pot in our winters is to avoid cheap terracotta cracking in a heavy freeze, if we get one this year. The rosemary itself will be fine.

I've struggled for years with overwintering rosemary indoors. Nope, none have survived outside - tried that, too. A couple of things I've tried that seem to work:

Since rosemary is native to a Mediterranean climate, they get most of their rain from October through February. Besides, it's fun to check the weather in Rome and see if I need to water my rosemary and bay laurel. I've been watering much more than I thought was right, but I have managed to overwinter rosemary for two years now.

I read somewhere that rosemary doesn't like abrupt changes in the amount of sunlight it gets. I move mine gradually into the house over a period of 3 - 4 weeks.

Since mine is manageable and lives close to the door, I put it outside during the winter if it's a "relatively" warm day and if I remember :-) Fresh air never hurt anybody, right?

My biggest problem is powdery mildew. Chamomile tea seems to be working the best, and since we eat the rosemary, I don't have to worry about chemical stuff. Linked below is a post from Richter's with a few other methods.

Hope that helps.

Here is a link that might be useful: Richter's Q&A

Uh oh. I've just bought some rosemary for my herb box.. .And it's going to have to be inside, because here in MN it can get to -35F and it just won't survive that. (Not to mention I rent my house and am not allowed to plant things outside in the soil...)

I'll keep it closest to the window. The greenhouse I bought it from was warm (like indoor temperature) but bright, and it was flourishing. I've got a grow light for that corner, so hopefully that combined with the windowsill light can keep it alive. Maybe I should crack the window to let in some air now and then? A quick google search says cool and sunny... I'll see if I can manage that!

cfox248 - have you planted your rosemary with other herbs in a single box? That is not really a good idea as herbs are not a homogeneous group. They all need different amounts of water and nutrients. For example, what suits mint will not suit basil. What suits parsley will not suit rosemary.

Most greenhouses buy their plants in so the conditions in the greenhouse where you bought it are not necessarily the ideal conditions for growing the plant long term. The conditions have to suit the human purchasers as well as the plants.

Key info is that rosemary is from the Med. It isn't tropical so it needs a cool but not deep frozen winter, fast draining medium, good air circulation and not too much water. If it were in a pot of its own I'd even recommend putting it outside on mild days to get some fresh air or a shower of rain.