I am building a greenhouse into a bank so it will be partially in the ground and receive ground heat/warmth; I am wondering how much and what we can grow in the winter here. We live in the coastal mountains of Oregon - fairly mild winters.
You can grow all the greens you could possibly want. Eliot Coleman's book, the Four Season Harvest, is my go-to reference book.
The basics: time the winter crop to reach maturity just as it gets so cold as to stop growth. Your salads go into a hibernation but stay in good condition all winter.
Here, in Zone 5, I want my greens to be harvestable by mid-October. Growth is essentially none until late February. In a protected environment in Oregon, your dates will be much later. You might even be able to go year round.
Spinach and kale are bullet proof. Some lettuces are a bit fragile-we like Black Seeded Simpson and anything with "Winter" in its name. Tatsoi and mach are our new favorites.
swiss chard will reseed and grow year after year in your greenhouse, and most greens and herbs grow well in winter in the greenhouse..look for cool weather crops ..those that like cool weather for growin in the greenhouse..tomatoes and peppers do well in the summer inside the greenhouse..I'm in Michigan..don't bother with anything you can easily grow outside..you won't have that much room. I have tried melons and squash in the greenhouse and they actually did better out in the open ..but that's just me.
Bloom where you are planted.