Outdoor gardening gives you the opportunity to enjoy the fresh air and sun, but also limits your time to grow lush plants because rain and cold weather force you to retreat inside until a better day. A greenhouse allows you to garden year-round. Not only are you protected from the elements, your plants have the chance to grow in optimal conditions as long as the greenhouse has specific environmental controls, including heating and cooling.
Ventilation in Warm Weather
Most plants do not respond well to temperature swings larger than 15 degrees Fahrenheit, which can cause stunting and dieback. For successful year-round greenhouse gardening, the structure must have some form of air intake, like shutters, to allow air to enter the greenhouse during warm weather. Hanging fans move the air to simulate wind movement. Moving air prevents excessive heat from drying soils and reducing fruit sugar content. Additionally, constantly shifting air stops condensation from dropping onto foliage, which helps prevent bacterial and fungal diseases.
Heating in Cool Weather
If you live in a cooler region, you need heaters to warm the greenhouse. Although greenhouses have some insulation from the cold outdoors, most structures allow some drafts inside that decimate plants if there's no heater. Heaters must be customized for each greenhouse -- the space dictates the heater size and power output. You can choose heaters fueled by propane, natural gas or electricity. Choose a heater with a thermostat so it turns on automatically when the temperature drops below a certain level.
Another key to year-round greenhouse gardening is an irrigation system. Although you can water with a watering can, you may not have the time to properly cover the space if the greenhouse is particularly large. Tube watering systems water directly at the roots, keeping the foliage dry. You can also install misters, either on the ceiling or beams. Misters are automatically controlled by timers so you can control watering based on the plants' needs.
Because heating and cooling your greenhouse year-round consumes a large chunk of your energy bill, it is good practice to conserve energy where you can. Any north-facing wall need to be insulated with extra plastic or plywood. Because sunlight is minimal in this direction, you are not sacrificing necessary light and heat. Shoring up the entire greenhouse covering with an extra layer of plastic is another option. Double plastic layers, trap an air layer in between to provide insulation.
- University of Georgia: Hobby Greenhouses
- West Virginia State University Extension Service: Planning and Building a Greenhouse
- Virginia Tech Cooperative Extension: Dealing with the High Cost of Energy for Greenhouse Operations
- University of California Davis: Year-Round Gardening With a Greenhouse
- University of Tennessee: Controlling the Environment in Greenhouses Used for Tomato Production
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