Hello Alex,
I am going to go ahead and throw my voice in with Daron. I do think the biggest issue is going to be sunlight.
But I will go ahead and conjure up a thought that may or may not be helpful.
If you want to try a winter garden starting now, my thoughts are first off to start small. It is a whole lot easier and probably more productive to tend to a small garden as opposed to a large garden. Since it is mid-late December, I would also go with a relatively simple choice.
I would try growing in some 5 gallon buckets. Buckets will be cheap and easy to set up. I would try to grow in maybe 4 buckets with a 5th
bucket in reserve that I will get to in a minute. Fill your buckets with the absolute best potting soil you can get your hands on. Make some sort of frame covered with a transparent but durable plastic tarp or some other material. Years ago I replaced a French door with a slider. I had a friend who took the old French door and used it to make the lid of a cold frame, a lid he could open at will.
At any rate, make your frame. I think Daron is correct in that lack of sunlight is going to be a big problem. If you feel competent, maybe you could make a series of
incandescent grow lights to provide both light and heat. The downside of incandescent is that they use fairly high wattage and
LED lights will be safer and easier to install, probably have a better lighting spectrum, but will add almost no heat. I would be tempted to go with the LED’s.
This is where that extra bucket comes into play. I learned a long time ago that I could keep my childhood outdoor pet cat warm overnight if I put
hot water jugs in the back of his little crate that became his pet house. He stayed warm all night long—90 degree warmth when it was -25 outside and probably-15 in the garage. I would take that five gallon bucket and fill it with hot tap
water. Even better would be to boil some or all of that water just to make certain that it is hot. Put the lid on the bucket (make certain that you get a lid) and place the bucket in between the other buckets of garden soil. Make certain that all buckets are sitting on
wood or something other than cold ground or cement (even worse). That hot 5 gallon bucket will stay plenty warm all night and as long as you fill with
hot water just before going to bed. Check it in the morning but I cannot imagine that it would freeze unless it is directly exposed to freezing temperatures. Make sure that your little greenhouse/cold frame is protected from wind and rain (you don’t want water to leak into a moving part/hinge and then freeze—that’s bad). If you get really ambitious you might consider some styrofoam insulation to insulate the floor and sides. You can get this easily and cheaply from a hardware store. But this is strictly optional.
Getting good grow lights will provide the light you will need. You might even think about having a second reflective/opaque cover to both insulate and reflect light back in. But again. This is optional.
I would think that by giving your little greenhouse the 5 gallons of hot t water would provide plenty of heat. And if things just don’t work, since the plants are in buckets, you could easily bring them inside if you needed.
These are just my thoughts and take or leave them as you feel appropriate.
Best luck and please keep us updated. I for one am curious as to how your
project works out!
Eric