When you see fresh tomatoes in the produce section of the supermarket during December, January and February, chances are that those tomatoes are hot house varieties. Hot house produce are vegetables that are grown out of season in a greenhouse. The practice of growing vegetables during the winter months is what greenhouses were first developed for. Growing tomatoes, cucumbers and peas in a greenhouse can be undertaken as a small backyard project.
Set up your greenhouse for winter gardening. Choose a site that receives the maximum amount of light during the day. One easy-to-construct greenhouse is a hoop house made of PVC pipe bent into a horseshoe shape, staked to the ground with lengths of rebar and covered with a sturdy, clear plastic skin. In colder climates, the greenhouse can be heated by use of a compost pile in the center of the greenhouse, water-filled barrels for passive solar heat, or a specially manufactured greenhouse heater.
Construct a growing medium for your vegetables to support the root system. Greenhouse plants can grow hydroponically, in plastic containers or in raised beds. Plants such as tomatoes, cucumbers and peas that are grown in raised beds and containers will need at least 5 gallons of potting soil that has been enriched with compost for each plant. Root crops such as carrots and radishes can grow in deep tubs spaced more closely together. Spread your containers apart so they benefit from a maximum amount of air circulation.
Provide ample supports for plants that grow on vines, such as cucumbers, peas or tomatoes. A wooden trellis staked to the ground or a string trellis tied to the supports of your greenhouse are both options for trellising vine plants.
Place a thermometer inside your greenhouse, and monitor the internal temperature daily. If the internal temperatures become too warm, vent your greenhouse by opening it and allowing cooler air to flow into the structure.
Set up supplemental lights, such as a portable lamp with a solar light installed, to help plants get added nutrients that they cannot get from the sun during the shorter days of winter. This is especially important for plants like tomatoes and herbs that need approximately 11 hours of sun daily. Put your plant lights on a timer so that plants still get an adequate balance of darkness as well.
Install a fan in your greenhouse to help circulate the air in the room.