Those of us who are sad that our growing season has ended often think wistfully of a greenhouse or a sunroom.
Few pleasures in life exceed stepping into a hot greenhouse full of green growing plants on a cold blustery day, but there are some things to consider before getting involved with a greenhouse.
You'll need to cool that space as well as heat it. I use an electric heater, but my Sunglo greenhouse also came with cooling apparatus. That is, a set of ground-level louvers on the wall opposite an exhaust fan, joined to operate together when the thermostat climbs to 100 degrees. Since heating and cooling are both electricity-based, I can't tell how much it costs to heat the greenhouse.
Some "sun rooms" do not allow for cooling in their construction. You'd either have to use a fan or move the plants to prevent cooking them, I think.
If you want to grow food items in your greenhouse, you should consider light as well as heat. On those winter days that sunlight is available for less than 10 hours per day, plant growth is very slow. Unless you've started plants weeks earlier and they're on the brink of maturity, you won't get harvestable greens, for instance, unless you supply artificial light.
At our latitude, our sunlight hours are less than 10 hours each day from Nov. 8 to Feb. 4. Grow lights such as fluorescent shop lights (one cool bulb, one warm one) set on a timer for 12 hours each day should work.
Commercially-made greenhouse kits are available from about $500 up from Costco and $300 up from Harbor Freight Tools. You could also build your own of discarded windows (usually single-pane glass), or plastic over hoops. Johnny's Selected Seeds sells a tool for bending chain link fence top rails into hoops for houses tall enough to allow the gardener to walk upright - or, once you see the price, contrive your own bending tool.
It is a great benefit to have running water available in your greenhouse, as well as the electricity used for a cooling system, at least. You may choose not to heat your greenhouse at all, or use a wall or barrels of water or something to absorb daytime heat and release it slowly at night, or roof vents to remove heated air.
You'll need benches, on which to set plants and/or pot plants. Coated wire shelving, such as that used in closet organizers works very well. It's easily cleaned and relatively strong.
WAIT TO EAT SQUASH
Now that you've harvested winter squash and dug sweet potatoes, give them a rest before eating them. They need time to "cure" and convert their starches to sugar before they'll be at their tasty best. A greenhouse is a good place to heat curing produce, but it should be augmented with humidity.
SEEDHEADS FOR THE BIRDS
If you haven't already cut down annuals and perennials that have seedheads, please leave them. Many birds prefer to pick their own, and will feed on those seeds, but will not eat commercial birdseed. Oregon Juncos, our usual winter bird, never visit our bird feeders, but they'll land on a sorrel seed stalk, ride it to the ground if it bends, and eat those or any seeds they find on plants.
Send garden questions to firstname.lastname@example.org or Gardening, The Statesman, P.O. Box 40, Boise, ID 83707.