Growing tomatoes in a greenhouse is a great way to enjoy the rich, plump fruit all year long without the worries of weather elements. Tomatoes can grow anywhere from three to 10 feet in height, and come in dozens of varieties, most notably the delicious and historical heirloom tomatoes. This fruit contains lycopene, a powerful antioxidant, as well as vitamins C and A. The key to growing tomatoes in a greenhouse is ensuring that the soil is prepared correctly and that the fruits receive sufficient sunlight and water.
Prepare the proper soil. Mix potting soil mix (equal parts perlite, peat and vermiculite) with about 10 percent worm castings added. Add a teaspoon of lime per gallon of soil, to adjust the pH and ensure prevention of blossom end rot in tomato plant when they are maturing. Moisten the soil slightly before planting the tomato seeds. Fill the seedling trays with this soil.
Plant each seed 1/4 inch deep, and about 8 seeds per inch. After planting, spritz with a water bottle to moisten and cover with a damp cheesecloth for a couple days to prevent drying out. The ideal temperature for tomato seed germination (which takes place in about one to two weeks) is around 80 degrees Fahrenheit.
Remove the damp cheesecloth as soon as the tomato seeds begin sprouting. Keep these sprouts in full sunlight for 12 hours a day. If this isn't possible, use grow lights.
Transplant the seedlings carefully to the 6-inch planter pots once they are 1 1/2 to 2 inches tall. Do this by tugging the seedlings up with your fingers and setting them into a hole you made with your finger into the new planter pot's soil.
Water the tomato plants to keep the soil consistently moist, but not soaked, about once deeply every couple days.
Continue to provide 12 hours of sunlight to the tomatoes. Once they are about 4 inches tall, fertilize with a 16-16-16 fertilizer. Try to keep an ideal temperature for maturation of about 73 degrees Fahrenheit during the day and 65 degrees at night.
Transplant the tomato plants to a 1-gallon planter pot once they are 12 inches tall or more. Scoop up the plants underneath with a trowel and bring them to the pot that has prepared soil already in it.
Observe your tomato plants, as they should start to flower within six to eight weeks, which will induce fruiting during the months thereafter. Harvest tomatoes once they appear heavy on the branch and are a firm, rosy red.