Simply put, a greenhouse tomato is one that has been grown in a greenhouse. Rather than a temporary warming tent or a simple support structure, the greenhouse in question is usually a permanent structure. Any tomato can be grown in a greenhouse, though most small kitchen garden greenhouses only hold the smallest varieties. Greenhouse tomato plants are most likely to be found in areas that experience extreme weather changes.
Tomato plants that are started in a greenhouse and then transplanted to an outdoor garden are not technically greenhouse tomatoes. Tomatoes that have been transplanted grow throughout the summer and die back in the fall. Every year, gardeners with outdoor gardens must plant new outdoor tomato plants. A traditional greenhouse tomato plant will grow all year, but will only bear fruit during the growing season.
When greenhouse tomatoes are forced to produce fruit all year, the result is often small, inferior tomatoes. As a result, many gardeners reduce water usage and lower greenhouse temperatures slightly during the cooler months to simulate a sub-tropical winter. Tomatoes can establish new roots and store nutrients for the following growing season during this period of dormancy. When spring arrives, gardeners fertilize their greenhouse tomato plants and increase the frequency with which they are watered to signal to their tomatoes that it is time to grow.
Though any tomato species can be grown in a greenhouse, larger varieties like beefsteak and heirloom are usually only found in large industrial greenhouses. Plum, grape, and cherry tomatoes are usually grown in small hot houses that are only meant to feed a single family. These dwarf varieties require less space to grow and can even be shared with other plants in the same pot. These tiny tomatoes can be anywhere from the size of a coin to the size of an egg.
Gardeners can choose from a variety of greenhouse types. Industrial greenhouses, which grow tomatoes all year, can be hundreds of yards long and hold thousands of plants. The average home gardener’s greenhouse is about the size of a small storage shed. Those with a limited amount of space can construct greenhouses that can only hold one pot. Others may prefer to build indoor greenhouses by lining the walls of a sunny spare bedroom with plastic shelves. A warm, well-lit, climate-controlled space is simply referred to as a greenhouse.
Growing greenhouse tomato plants can be done in a variety of ways. Planting the tomatoes in a pot with topsoil, potting soil, or vermiculite is a common traditional method. Hydroponic gardening is a popular non-traditional method. Plants are placed in small mesh baskets filled with aquarium gravel in this method. The mesh baskets are submerged in a moving water bath containing liquid fertilizers and salts. Tomato plant roots wrap around aquarium stones, absorbing nutrients from the water directly.