tomatoeseedlings...I have some which are 2 years old in my greehouse.
lettuce, spinach, peas, beans, patatoes, cucumbers. herbs, mint, and theres more but my brain is shutting down.
Since you have extended your season with a greenhouse I would garden like those who garden in the Virginia area perhaps? Go to one of their forums and lurk around.

If you're looking to farm in there, plant some things that don't need a lot of heat. 1 plant of a hundred things is not a good way to do it until you learn what your greenhouse climate is. Keep in mind that good air circulation is as important as any heat you may be trying to capture. Lettuce is easy, but also prone to aphids. You could really extend your season if you pick plants like Brussel sprouts that can take heavy frost without turning into a brown worthless plant. The other members of the Cole crops are also useful (cauliflower, brocolli, etc). Leafy greens and radishes are quick and will grow in cool soil.

Since you will gain about one zone, even without heat, when you see us planting outside, it will be time for you to sow indoors (springtime). If you heat it even a little, you will be surprised at the gain. Mine is glass (poorer insulation than a double wall plastic), and I figure that the temps have to drop to very low 20's F (about 22°F) before it would freeze inside. So even without heat, I gain about 10 degrees F.

I've found mine great for growing tomatoes,peppers and cukes and getting them to ripen, which seem next to impossible for me to do out in the "open" garden. Next year I'm going to try eggplant and melons, like cantalope too. I've also had good luck with leaf lettuce real early in the season. It gets to hot later, that's where the maters, peppers and cukes come in, they love it hot!

Cathy

I had watermelon in my greenhouse as big as 20" around by the end of May! That is a greenhouse with heat on (propane)
and no additional light.

I dont generally use heat mats, if you can believe that for us here in MIane! I like to just grow when mother nature is most stronger to help, but I do use the greenhouse.

I winter sow on the winter solistice every and all I can, then I place everything in a cool green house with the heat on only to 50F. That is in December. Later in March, I raise the heat up to 70 and turn it off completely by May. (so, I do help fake conditions somewhat)
Plants respond well to my methods, though.

I also use organic compost teas as a constant feed. Apply as a weak tea.

Hi susie...the green house is gonna be unheated for now....just wanna stretch the season on each end some. It's wify who wants it close to the house to grow greens in etc...:-)
I have some land out behind my house that I want to clear...abt three acres...to start growin' tomatoes in a big way. The land slopes to the south and is protected by trees in the right place. Am also on the York river so I have water for the plants. Franklin

i think i "talked" to you once, e mail? anyway , after the last winter, how did your greenhouse do? and your raised beds? reason i'm curious, i'm going to combine a raised bed-concrete blocks, 3 high, with a hoop house this winter. start small,and see how it does. being in zone 6, i'm warmer than you, --but--just curious.

You might want to also check out the book "Four Season Harvest" by Eliot Coleman. If you build a cold frame hoop system inside the greenhouse, you should be able to harvest cold hardy items such as spinach in the middle of february. Good luck with the new greenhouse :)

I've had luck with spinach, arugula, beet greens, kale. Territorial Seeds, Cook's Garden, and maybe a few other seed houses have special mixes of cold hardy lettuce -- I'm trying some this year.

Coleman's book is good. I visited his GH when I was setting mine up. One thing he pointed out was that you're just not going to get anything to grow in December and January without heat and light, so just throw a row cover over your greens and let them "hibernate" until the longer days wake them up again.

I've tried peas -- in the spring you can get them in early but I found the temps in the GH got too hot too early. Next year I'll try a fall crop, planting in August.

I really hope you enjoy your GH. I think "cold" is the way to go, a lot less insects that way. And don't overlook a row or two of tulips -- plantr them now and you can have some beautiful flowers in March.