A greenhouse is designed to control most of the environment surrounding the plants. Computer controlled variables include the temperature, moisture level, nutrient elements. Optimization of these variables enhances productivity, flavor and quality.
Most growers use hydroponics: the growing of plants in media such as rockwool using nutrient solutions. Rockwool, an inert growing medium with excellent water-holding capacity, eliminates the need for soil sterilization, helps produce better quality crops with reduced energy for a longer harvesting period, and provides a cleaner working environment.
Another hydroponic growing technique is the Nutrient Film Technique: a water-culture system based on circulating shallow film of nutrient solution over the roots of plants to provide water, nutrients and oxygen.
All Ontario greenhouse tomato growers use "beneficial insects" instead of pesticides for pest management. The concept is simple: good bugs eat bad bugs. Strips of yellow sticky paper are set out to catch and count the pests, and predators or parasites are released accordingly. It is a virtually pesticide free way of keeping crops healthy. Bumble bees are used to pollinate tomato flowers resulting in improved fruit quality and labour efficiency.
Tomatoes are a good source of Vitamin C and a source of Vitamin A, folacin and potassium.
The first experiments with greenhouse horticulture were conducted by the ancient Romans. It wasn't until the Victorian period, when it became possible to properly control ventilation, heating and irrigation, that the industry began to grow. Greenhouse vegetable growing in Ontario became popular shortly after World War I.