What is Greenhouse?
[[File:Botanischer Garten BS.Seerosen.jpg|thumb|Inside a greenhouse]] A '''greenhouse''' (also called a glass-house or hothouse) is a building where plants such as flowers and vegetables are grown. It usually has a glass or translucent plastic roof. Many greenhouses also have glass or plastic walls. Greenhouses warm up during the day via penetration of the sun's rays which heat the plants, soil and structure. This heat is given up gradually throughout the night. ==Types of greenhouses== Greenhouses come in many shapes and sizes, with different functions. Some people have small greenhouses in their backyard, or as a lean-to attached to their home, called mini greenhouses, or tomato houses. They want to start off their seeds and seedlings in a protected environment as well as those growing plants that need warmer conditions. Others, wishing to extend their living space, have house extensions in the form of mini-conservatories. Commercial companies usually have larger greenhouses for horticultural purposes, but have more substantial structures for plant displays where the public is admitted. For the same reason, botanic gardens usually have a high proportion of greenhouses with substantial structures. ==Role of greenhouses== Many vegetables and flowers are grown in greenhouses in late winter and early spring, when it is still too cold to grow plants outside. Then these plants move into the soil outside as the weather warms up. Greenhouses are used to grow crops in cold countries such as Canada. The largest group of greenhouses in the world is in Leamington, Ontario (in Canada), where about 200 acres (0.8&nbsp;km²) of tomatoes are grown in glass greenhouses. ==Gardening in greenhouses == [[File:JardimBotanicoCuritiba.04.2008.JPG|thumb|right|A glasshouse in the [[Botanical Garden of Curitiba]], in [[Curitiba]], [[Brazil]].]] [[Gardening]] and growing plants in greenhouses is different from growing plants outside as no rain can get inside a greenhouse, so gardeners have to water plants. Also, greenhouses can get ve