Greenhouse gardening is an ideal way to have year-round production of plump, rich tomatoes. Not only do you not have to worry about any elements outside, but you can also control all the aspects of growing your tomato plants. When growing tomatoes in the greenhouse, it is important to prepare the soil properly and provide sufficient lighting, whether it is artificial or natural.
Mix potting soil with 10 percent worm castings added, along with 1 tsp. of lime mixture per gallon of soil. The lime will help prevent rot during maturity. Spritz the soil with a water bottle to moisten it before panting the seeds. Layer the soil into the seedling trays to the top.
Push each tomato seed into the soil about 1/4 inch deep, with six to eight seeds per inch. Mist the soil again to moisten it. Continue to do this a few times per day so the seeds don't dry out. Also, keep the temperature around 80 degrees Fahrenheit for seed germination, which should occur within two weeks.
Place the seeds in full light for 12 hours per day, using natural light coming through the greenhouse or artificial grow lights.
Transplant the seedlings once they are about 3 to 4 inches tall to the 1-gallon planter pots. Gently tug them up out of the seedling tray soil with your fingers and set them carefully in a shallow hole (about 1/2 inch deep) made with your finger.
Water the plants deeply every few days so the soil is kept constantly moist, but not soaked.
Place the tomatoes where they'll receive 12 hours of sunlight, with an ideal growing temperature of about 74 degrees Fahrenheit during the day and 66 degrees Fahrenheit at night. Once they are about 5 inches tall, fertilize with a 16-16-16 fertilizer. Maintain the temperature, watering cycle and sunlight on your tomato plants until they begin to flower. This should occur within six to eight weeks.
Harvest the tomatoes after fruiting when they appear large, a rosy red color, firm and heavy on the branch.