A short growing season and cold winters makes greenhouse gardening a natural choice in Michigan. Besides starting transplants, greenhouse gardening allows you to enjoy gardening during the other seasons, too. You can even grow fresh vegetables year-round in your greenhouse, giving you tasty, healthy food in winter.
The best place to build a greenhouse requires a location where plants can get the most sun possible. In Michigan, greenhouses work best on the south or southeast side of a building, where they receive adequate morning sunlight. If you plan to primarily grow plants to be transplanted outside in summer, consider building your greenhouse on the east side of the building. During the winter, the east side of buildings get the most light, making it ideal for short-term winter or early spring growing.
Greenhouses range in size from small window frames you attach to a south-facing window to full-blown buildings erected separate from your house. Window greenhouses offer two or three shelves to hold a variety of small plants. Some gardeners prefer lean-to greenhouses where one long wall is attached to the house. Another type of greenhouse, the even-span, requires one of the shorter walls to be attached to another building. Passive solar greenhouses are separate buildings that use sunshine to heat the inside.
Greenhouses consist of frames and covers. Frames can be made from wood, steel, aluminum or metal pipes. Some greenhouses use plastic pipe materials, similar to those in plumbing systems. While those systems tend to cost less money to build, plastic pipes may not stand up to the windy conditions in Michigan, especially during blizzards. Greenhouse covers are made from glass, plastic film, fiberglass or double-wall plastics.
You'll need to water your plants each day, sometimes more than once a day, when using a greenhouse. Automatic watering systems make the job easier. The trick is determining how often you need to water based on the kinds of plants you're growing, the containers they're growing in and the soil mixes you're using. You'll also need mist sprayers to increase the humidity in the greenhouse, especially in the winter when the air gets dry.
Michigan's cold winter days and nights make a heating system a necessity in the greenhouse. You'll even find that your greenhouse needs heat during the spring and fall, too, when temperatures start to cool down at night. Small greenhouses may benefit from a 220-volt circuit heater.