greenhouse, enclosed glass house used for growing plants in regulated temperatures, humidity, and ventilation. A greenhouse can range from a small room carrying a few plants over the winter, to an immense heated glass building called a hothouse or conservatory, covering acres of ground and used for forcing fruits or flowers out of season. Greenhouses have long been used for holding plants over cold seasons and for growing tropical plants and less hardy fruits, but only in this century has the greenhouse been used for forcing vegetables. Now millions of dollars' worth of plant products are raised yearly in greenhouses. See cold frame.
See A. Laurie et al., Commercial Flower Forcing (6th ed. 1958); H. Ibbotson, Build Your Own Greenhouse (rev. ed. 1965); H. T. and R. T. Northen, Greenhouse Gardening (2d ed. 1973).