Greenhouses are used all over the world as a means to grow plants in a controlled environment where outdoor growing is unfeasible due to soil or weather conditions. Using greenhouses, it is possible to grow summertime plants even during the winter and to grow plants in climates where they would never be able to perform naturally. Plants grow better in greenhouses, because gardeners can better control the conditions under which they grow.
Warmth Is Key
Plants, like animals, need just the right temperature in which to thrive. If the temperature drops too low or rises too high, the plants are hindered or, worse, they die. The appropriate temperature ranges with the plants, with temperate plants like potatoes doing well at relatively low temperatures and tropical plants like oranges doing well only in warmer climates. Greenhouses provide the warmth needed for plants to grow in cooler times and regions than they would normally.
Greenhouses, depending on how they are built, may simply extend the growing period for a short time or may serve as a self-contained climate. Greenhouses have a transparent roof that allows the space to collect sunlight and heat and let minimal light and heat escape. This raises the temperature within the structure and keeps plants warm. Greenhouses that use only this natural, sun-powered method of temperature control are called "cold houses," since, though they will keep a warmer temperature than the outside world, they will still see a dramatic drop in temperature during the winter.
Besides "cold houses," there are also cool, warm, and hot houses which have an additional method of heating besides the trapped sunlight. These ensure that, even during cold winter months, plants that require warm or hot weather to thrive will keep that environment.
Greenhouses used to be hobby projects for wealthy gardeners, but now they are commonly used in commercial agriculture to grow food crops in environments where they otherwise would not be able to grow. For example, using greenhouses, it is possible to grow tropical fruits like oranges or pineapples in temperate regions, cutting down on the costs required for shipping these fruits from tropical to temperate regions.