Another magazine for northern gardeners is People, Places & Plants. This started out as a magazine for Maine gardeners, then expanded to cover all of New England. Checking their website before posting this link, I see they are about to start a second magazine for the Mid-Atlantic region. I haven’t actually seen an issue since the first year of its publication. At that point I found it to be a magazine worth browsing for the inspiration of other northern gardens, but not having enough how-to to make it worth paying for. Obviously they are doing well, so there must be plenty of people who do find them worth subscribing to.
I have also looked at Northern Gardener, the magazine of the Minnesota Horticultural Society. They had an informative article on hardy evergreen rhododendrons being bred in Finland in the sample issue I looked at, and I almost subscribed. I probably found a plant I needed more that month. Definitely worth a look.