How to Plant Tomatoes in an Greenhouse
Tomatoes keep fruit prolifically and need very little care, so they’re one of the most popular vegetables for house gardens. Adequate warmth and long, sunny days are necessary for the plants to bear fruit, therefore they are only productive during the summer and fall months within U.S. Department of Agriculture plant hardiness zones 8 to 10. But planting tomatoes within a greenhouse will effectively expand the growing season and permit the plants to keep year-round, if they’re supplied with the appropriate light, dirt and temperature conditions.
Plant determinate, or bush-type, tomatoes in greenhouses rather than indeterminate varieties since the latter develop very large and will take up too much space. Choose cultivars such as “Legend,” “Patio Hybrid” and “Cherry Grande Hybrid.”
Plant greenhouse tomatoes in fall or early spring for a late or early return. Start the seeds indoors four to six weeks before transplanting them into the greenhouse to ensure they are older and hardened-off.
Ready the greenhouse before planting the tomatoes. Hang 10-percent shade fabric along the southerly wall of the greenhouse to prevent sun scald. Place a garden bench along the wall. Position a thermometer near the garden bench to track the temperature.
Pot the tomatoes in 5-gallon containers filled with a soil mixture of 3 parts loam, 2 parts compost, 1 part coarse sand and 1 part perlite. Plant the young tomatoes so the foundation of the stem is 1/2-inch below the surface of the ground to help produce sturdier, stronger plants that are mature.
Place the tomatoes on the garden bench near the thermometer. Supply water when the soil mixture feels dry at the upper inch. Feed the plants using low-nitrogen, 5-10-5 fertilizer one month after planting. Apply the fertilizer at half-strength. Feed once a month and water thoroughly after each feeding.
Preserve a constant daytime temperature of 70 to 80 F and a nighttime temperature of about 65 F. Do not allow the temperature to drop below 65 F at night since the fruit will become mealy and unpalatable. Do not let the greenhouse heat over 85 F since the fruit is going to be discolored.
Open the ventilation conduit to circulate the warm air and eliminate excessive moisture, which helps prevent leaf spot and blight. Turn on an oscillating fan if the temperature rises above 85 F or if relative humidity shirts 70 F.
Provide supplemental light using greenhouse lamps with fluorescent bulbs. Position the lamps approximately 3 feet over the tomato plants. Angle the lamps so the light glances off the tops of the plants. Turn on the lamps through the winter months when there is less than eight hours of direct sunlight.
Watch for signs of diseases such as leaf spot and blight, which are especially common in greenhouse conditions. Start looking for small lesions on the leaves or wilted foliage. Remove and destroy the afflicted plants to prevent the illness from spreading.