Growing fresh tomatoes in a home greenhouse is very rewarding process. In two to three months, you’ll have more fresh tomatoes than you ever imagined for salads, salsa, and fresh tomato sauce. Most varieties produce fruit in 60-80 days when grown from seed. However, purchasing transplants from a home improvement store is the fastest way to harvest tomatoes grown in the greenhouse.
Tomatoes come in every size, shape, and color. Selecting a crack-resistant and disease-resistant variety is important for tomatoes that are going to be greenhouse grown. Buying transplants at the home improvement store is a good solution, but growing from seed can offer more variety. Seed packets include detailed information, such as the time to harvest, uses for the tomato, disease resistance, and whether the tomato is determinate or indeterminate. Determinate tomatoes, including most paste tomatoes, produce one large harvest. Cherry tomatoes and large beefsteaks are indeterminate and produce fruit all season long until they are killed by frost. Indeterminate varieties can grow over 6 feet tall, so they may not be the ideal choice for a small greenhouse. Today, there are dwarf varieties available that produce abundant harvests of cherry, grape, and pear tomatoes. Dwarf varieties and determinate varieties are excellent for container growing in the greenhouse.
Tomato seeds usually spout in one to two weeks. For the first few weeks, seedlings can be grown with supplemental light. When seedlings have they second set of true leaves, they should be transplanted into individual pots. Once the seedlings are about a foot tall, they should be transplanted again into large one to three gallon containers.
Soil is an important consideration for growing tomatoes in the greenhouse. Commercial potting soil contains peat for water retention with perlite and vermiculite for drainage and aeration. Peat is naturally acidic and tomatoes prefer soil that is closer to a neutral pH. To sweeten potting soil and prevent blossom end rot, add a small amount of lime when repotting.
Tomato seedlings should be fed with diluted applications of a well balanced fertilizer with equal N-P-K numbers. After the tomatoes have been transplanted to their final container and up until flowering, they should be fed with a bloom booster fertilizer that contains large amounts of phosphate and potassium. Look for a fertilizer with a low number followed by two high numbers, representing nitrogen, phosphorus, and potassium respectively. For the rest of the season, greenhouse tomatoes should be fertilized with a well balanced fertilizer.
Support and Pruning
Tomato cages are excellent for supporting potted planted in the greenhouse. Stakes also work but metal cages tend to provide support to more parts of the plant. To keep the tomato plants healthy and well maintained, the suckers that grow off of the leaf bases should be snapped off. Suckers form branches that rob energy from fruit production. Pinch off the tip when suckers are woody, leaving one set of leaves to prevent pathogens from entering the main stem.
Flowering and Pollination
After about six weeks, the tomato plants should begin branching and flowering. Tomatoes are sensitive to the length of the day, so they need at least 12 hours of darkness to flower. Because greenhouses are isolated from natural pollinators, tomatoes must be hand pollinated to set fruit. To imitate nature, the plant’s stems and the tomato cage can be vibrated with a battery-powered tooth brush to release the pollen. For best results, greenhouse grown plants should be pollinated every day around noon. After the plants are pollinated, the tomatoes will ripen, awaiting the first harvest.