A greenhouse tomato is simply a tomato that has been grown in a greenhouse. The greenhouse in question is usually a permanent structure rather than a temporary warming tent or simple support structure. Any kind of tomato may become a greenhouse tomato, though small kitchen garden greenhouses usually only hold the smaller varieties. One will likely only see greenhouse tomato plants in areas that experiences extreme weather changes.
Technically, tomatoes that are started in a greenhouse and then transplanted to an outdoor garden are not greenhouse tomato plants. Transplanted tomatoes grow throughout the warm season and die back when autumn arrives. Gardeners with outdoor gardens must often plant new outdoor tomato plants each year. A traditional greenhouse tomato plant grows all year round, though it may only produce fruit during the growing season.
Forcing greenhouse tomatoes to produce fruit all year can sometimes result in small, inferior tomatoes. For this reason, many gardeners reduce water amounts and turn the temperature down slightly in the greenhouse during the cooler months to simulate a sub-tropical winter. During this dormancy, the tomatoes can establish new roots and garner nutrients for the next growing season. When spring comes again, gardeners usually fertilize their greenhouse tomato plants and water more frequently to signal their tomatoes that it is time to grow.
Though gardeners may grow any tomato species in a greenhouse, the larger varieties, such as beefsteak and heirloom, are usually only found in large industrial greenhouses. Small hot houses, meant only to feed a single family, usually house plum, grape, and cherry tomatoes. These dwarf varieties require less room to grow and may even share a pot with other plants. These little tomatoes often range in size from no larger than a coin to the size of an egg.
Gardeners also have many options for types of greenhouses. Industrial greenhouses that grow tomatoes all year round may be several hundred of yards long and house thousands of plants. The home gardener’s greenhouse may only be as large as a small storage shed. Those with extremely limited space may build greenhouses that are large enough to only hold a single pot. Others may prefer to construct indoor greenhouses by stacking plastic shelves along the walls of a sunny spare bedroom. The term 'greenhouse' simply refers to a warm, well-lit, climate-controlled space.
Several methods exist for growing greenhouse tomato plants. Traditional methods usually include planting the tomatoes in some kind of pot with topsoil, potting soil, or vermiculite. A popular non-traditional method features hydroponic gardening. In this method, plants are placed in small mesh baskets filled with aquarium gravel. The mesh baskets sit in a constantly moving water bath that is treated with liquid fertilizers and salts. Tomato plant roots wrap around the aquarium stones and absorb nutrients directly from the water.