Avid gardeners may find cold weather dispiriting with its barren landscapes. You love watching plants grow and appreciate consuming the product of your efforts. A greenhouse can keep plants growing through the winter. When you have a greenhouse, you can start seedlings for later transplanting, produce cool weather-crops like lettuce, or grow flowers for cutting. Greenhouses can be expensive and require a lot of effort and expertise or you can construct one for a relatively modest investment.
An attached or lean-to style greenhouse uses one side of your home for support and builds out between 2 and 8 feet with a sloped roof beginning at the roof eaves. The lean-to greenhouse provides easy access to water and heat. Your lean-to style greenhouse needs a built-in door or to be placed against a door of your house or garage.
The lean-to greenhouse usually has an aluminum frame covered with polycarbonate plastic sheets or glass. Because the inside of the greenhouse can become too hot on sunny days, it is desirable to have a vent in the roof or side to release heat. Inside the lean-to, shelves can hold plant containers. The south or southeast side of the house, with sun exposure, is the best location to keep your plants growing through winter.
Freestanding greenhouses for winter plants are located on their own site away from your house. They may be small such as a 4- by 6-foot hobby greenhouse or large buildings capable of producing commercial quantities of winter vegetables and flowers. Frames for freestanding greenhouses may be aluminum or steel and the coverings made of glass or polycarbonate plastic sheets.
The possible shapes of a freestanding greenhouse include A-frame, Quonset hut, barn-shaped, or post and rafter. The freestanding greenhouse needs a door, vents and access to water and electricity. Plan on adding heat during cold winter nights and venting or rolling up curtained sides during the days when radiant heat could make the inside too warm for the plants.
A cold frame is one of the simplest types of greenhouses to keep plants growing through the winter. With a few basic construction skills, you can build it yourself. A cold frame greenhouse uses an old window or storm door as its top. The glass object is attached with hinges to a constructed wood frame that is higher in back than in front. The angled glass allows for maximum sun exposure when facing south during winter months.
Prepare the area for your cold frame by removing any green material from the soil and turning it. Optionally, you can place landscape fabric to keep grass and weeds from invading the cold frame. Place the cold frame on the cleared surface and fill about half way with potting soil. Add seeds for cold-tolerant plants and water. During cold winter nights, close the top of the cold frame and cover with a blanket if the temperatures are in the teens or single digits.
During the day, open the frame to ventilate. Harvest your young tasty plants after eight to 10 weeks.