Can You Grow Vegetables in a Greenhouse Year Round?

Greenhouses use windows to hold in heat.

Greenhouses trap heat from the sun to create a warm environment for growing plants. Depending on heat levels, greenhouses can either extend the growing season by several weeks or allow for year-round vegetable growth.

Significance

The windows of a greenhouse allow solar radiation to enter. As the ground and plants inside the greenhouse absorb the radiation it is changed to thermal radiation, or heat. Thermal radiation has a different wavelength than solar radiation, and it is unable to exit the greenhouse through the glass panes.

Types

Greenhouses can be built in many sizes, shapes and locations, but the four main types of greenhouses are "cold" houses, "cool" houses, "warm" houses and "hot" houses. "Cold" greenhouses depend solely on the heat from the sun to heat the greenhouse, and "cool" greenhouses use additional heat to stay at temperatures just above freezing. "Warm" and "hot" greenhouses use a supplemental heater to maintain consistent temperatures.

Considerations

Vegetables cannot grow year-round in a "cold" greenhouse because the heat inside is not enough to overcome the freezing temperatures outside and in the ground. If planning year-round greenhouse gardens, install a supplemental heating system for use in the winter. Also remember that high temperatures can affect plant growth. All greenhouse types need ventilation and air circulation.

References

• Alaska Science Forum: How Do Greenhouses Work?
• TLC Home: Types of Greenhouses