Okay, first you need to take a look at Eliot Coleman's "Four Season Harvest," a great book and much talked about here. He's very interested in gardening in the parts of the year that are non-traditional here in the USA, but more common in other parts of the world. However, Coleman is primarily addressing market gardening, with big equipment (high tunnels of 24'x100' or something like that). He's good for the overview, but for the more common garden scale, look at Jeff Ball's 60 Minute Vegetable Garden. I read this one first, and had my first successful winter garden of carrots, spinach, and beets in a plastic tunnel on poly pipes based on Ball's model.

Understand that my zone 5 is sunny and dry, with a couple of 5-10 inch snow storms per winter, then the snow melts off and it returns to sunny and dry. You don't need the sunny part, as the intent is to get your winter-harvest plants as full-sized as possible before they slow down to nothing (About Thanksgiving here), but you may need to put the poly pipe ribs closer together to support snow load on your tunnel.

So, starting now, get your hardy fall seeds planted. Carrots, winter radishes (common seed display "watermelon" radishes are winter radishes), turnips, and beets can be direct seeded. So can spinach, chard, and lettuce, Chinese cabbage, and chicories. I put a thick row cover (frost blanket) over it and water well. This keeps the seeds damp in dry conditions, and keeps them from getting washed away if you have heavy rain. Check daily after about a week, as spinach doesn't like the row cover. Remove as soon as you see green. Sow again every two weeks until September. It may be a bit late to sow seeds for cabbage, kale, Brussels Sprouts, etc, but try with a short-harvest cabbage anyway (Golden Acre, 60 days?). These I start in 6-packs, but I grow them outside so they are already hardened off for transplanting when the summer beds are getting cleaned out.

BTW, flowering kale is sometimes sold as a bedding plant for the fall garden. It is hardy and edible, and tastes best after a frost. We have kale in a Tuscan white bean soup and a Portugese red bean soup, and my step-dad serves it braised. Yummy! I grow it outside of the tunnel, as it is so hardy, but you may want it inside the tunnel so you can find it after snow falls. Deer will eat kale (and cabbage) to the ground and go for more, so cage it if you have deer.

These are all cool-weather vegetables, so when the first frost threatens, mulch 6 inches deep between rows and set your poly pipes up (I just push the ends of mine 6 inches into the soil on either side of a 3 or 4 foot bed, as I do not have wooden boxes set up). When the first hard frost threatens (under 20 F) or snow is forecast, cover the poly pipes with your plastic and put another 6 inches of mulch in between rows. I just use heavy painter's plastic rather than a more expensive greenhouse plastic.

Harvest your beets, turnips, and radishes before the ground freezes. (You can use this, your first winter garden, to test when the ground under you tunnel and mulch freezes so you will know how long you can wait in the future. My ground stays cold but diggable just about all winter, but I have the advantage of solar heat in my tunnel.) Also dig a bunch of carrots for when you can't get to them. Lettuce will be the first of your greens to bite the dust, so eat your lettuce by Thanksgiving. Chinese cabbage and chard will probably be the next to suffer from cold, then the chicories and cabbage, and the spinach and kale may last all winter long if you don't eat it all. (We have become very fond of kale, which is a delicious vegetable when not grown in California where it never gets a touch of frost!)

Keep harvesting carrots as long as the soil is not frozen, and then start harvesting them again as soon as the soil thaws in the spring. Certainly dig them all in March (or as soon as possible), as they will start getting hairy as soon as their spring growth starts. I have a picture of my son (not available right now, darn!) holding a Purple Haze carrot 3 inches in diameter and 9 inches long dug last March. It was still crisp, sweet and tasty!

Starting in February, drop a few seeds anywhere in your tunnel that is empty, spinach, lettuce, carrots, spring radishes, and so on. I have to water mine (I live in a very arid climate), but you may have enough moisture in your tunnel to skip that. Clear out the mulch anywhere you no longer have mature plants, and pick out any slugs and snails you find (I feed them to my garden chickens). The nice thing about planting your late-winter and early-spring seeds under the tunnel is that the soil is drier than out in your snowy yard (I'm assuming you have snow cover).

After a winter garden, I use that bed for peas or beans to revitalize the soil a bit. And compost, of course.

Hope that helps.

Catherine

Here is a link that might be useful: Jeff Ball's 60 Minute Vegetable Garden