Where is the best placement of a greenhouse? What can be started in the fall/winter without heat?
I am wondering about backyard greenhouse placement. When south facing is recommended, does that mean the longer side of the greenhouse should face South or the door? Are there some things that can be started in a greenhouse without heat in the fall/winter?
When gardening sources recommend situating a greenhouse to be south facing, they are talking about the long axis of the structure–the goal is to maximize the amount of sunlight coming in and minimize shading from other plants. You would get the opposite with a short axis facing south.
As far as using an unheated greenhouse to grow into the fall and winter, there is a lot of good news, and a little potential bad news. The good news is that the greenhouse is an excellent method of *extending* your growing season, allowing you to grow later in the year and start earlier than you would in an outdoor garden, even if you don’t actually have it in production throughout every month. If you have one, you should absolutely use it to keep things going longer and get them started sooner than without the greenhouse.
The farther you want to push into true winter (on both ends of the growing season), the more extra effort you are likely to need to tend to your crops–in the coldest months of winter, the plants will most likely need extra protection like mulching and floating row cover to keep them warm at night, and the row cover will need to be taken back off during the day to maximize the amount of winter sun your crops are getting. Plus, keep in mind that you’ll need to be working in there yourself when it’s quite cold out! And you might lose some plants, though one other upside is that the conditions are inhospitable to many pests and pathogens, as well.
There is a lot of positive anecdotal evidence for getting successful winter crops from the folks who have been able to put in the extra effort. As far as crops go, you’ll be looking at typical cool-season crops that can tolerate lower light and the occasional nip of frost–more information can be found in this UMaine Extension resource on extending your growing season. Please also see UMaine Bulletin 1022 on the same topic (geared toward commercial growing but with good fundamental information, too).
You can also find some success stories from a couple of relevant, non-UMaine sources the Maine Farmland Trust and the Maine Organic Farmers and Gardeners Association.