Winter Greenhouses: How to Use a Greenhouse in the Winter

A greenhouse is an enclosure with a transparent roof and walls that let sunlight in, allowing gardeners to grow plants inside a controlled environment. Depending on the type of greenhouse, it may be constructed from glass and metal or a plastic material such as polycarbonate sheeting. Greenhouses can have any number of additions—including sun lamps, heating pads, air circulation, and water misters—to keep the plants inside healthy. There are many types of hobby greenhouses, including a cold frame, attached greenhouse, and freestanding greenhouse.

During the growing season, greenhouses rely on solar energy to heat the plants inside. In cool climates, a few extra measures are necessary to keep your greenhouse warm during the winter. Consider these tips for warming up your greenhouse for year-round gardening.

1. 1. Create a thermal mass. To prevent heat loss during the cold winter months, winter gardeners can create a thermal mass or heat sink inside their greenhouse. This can be done by placing a large barrel filled with water in a corner of the greenhouse. The water absorbs heat from sunlight and warm air during the day, then slowly releases it in the evening, protecting plants from the bitter chill of cold nights.
2. 2. Install a heating system. In northern regions, where winter temperatures drop well below zero, growers can use a convective electric space heater or, if the greenhouse is large, a heating system that can be controlled by a thermostat. Measure the square footage of your greenhouse to ensure the space heater you choose will provide enough heat.
3. 3. Insulate the interior walls. Products such as horticultural bubble wrap and horticultural fleece are specifically designed to insulate greenhouse interior walls, block drafts, and protect plant roots from cold temperatures while still letting light in. Check your local garden center for transparent insulating materials.
4. 4. Use grow lights. Grow lights not only keep your growing space warm, but they can also help provide additional UV light to encourage plant growth on dark winter days.

Greenhouse gardening makes it possible to grow a wide variety of vegetables during the cold winter months.

1. 1. Leafy greens: Cold-hardy leafy greens such as chard, collards, kale, and arugula are great for winter growing.
2. 2. Root vegetables: Root vegetables, such as turnips, carrots, and beets are also exceptional choices for winter greenhouse growing.
3. 3. Brassicas: Veggies belonging to the Brassica family, such as broccoli, Brussels sprouts, and cabbage can be grown inside an unheated greenhouse during the winter months.
4. 4. Alliums: Veggies belonging to the Allium family, including leeks, garlic, and scallions, do well in winter gardens.

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