If you'd like to grow grape tomatoes (Lycopersicon esculentum) but don't have space for a vegetable garden, don't be discouraged. Instead, grow a few plants in containers on a sunny porch or patio. It's relatively easy to enjoy a bountiful harvest from just a few potted plants, if you give them just a bit of special attention to keep the harvest coming.
A grape tomato is a small cherry tomato that's about 1 inch in diameter, the approximate size and shape of a grape. An especially prolific type of tomato, a single plant produces many dozens of fruits when given good growing conditions. Start seeds in trays or pots indoors about six weeks before your last frost date, or purchase seedlings from a nursery center when ready to plant. Either way, harden off seedlings by moving them outdoors for a few extra hours each day, planting them when nighttime temperatures stay above 45 degrees Fahrenheit.
When ready, choose a pot that's at least 20 inches across and 24 inches deep, with one plant for each pot. The pot must have at least one large drainage hole and can be plastic, which tends to dry out slowly, or clay, a more quickly drying material.
Soil, Sun and Water
A potted grape tomato needs loose, well-drained soil that's rich in organic matter. You can use a high-quality commercial mix, or make your own from equal parts potting soil, compost, sphagnum peat moss and perlite. Avoid using garden soil because it likely harbors insect pests or their eggs. Plant one seedling in each pot, setting it deeply so that the soil level is just below the first set of leaves; this stimulates roots to grow from the buried stem, promoting a strong plant.
Keep the pot in full sun for at least six to eight hours of sun daily; if your area has hot summer afternoons, choose a spot that gets sun mostly in the morning. Give the plant regular watering, moistening the soil thoroughly whenever its top inch or two feels dry to your fingertip; aim for at least 1 inch of water each week, including rain.
Supporting and Feeding
Some grape tomatoes, such as "Mighty Sweet," are determinate, reaching a maximum height in midseason; this type becomes naturally bushy and may not need support in its pot. But other indeterminate varieties -- getting taller all season long -- need support in their pot. "Red Pearl" is an example of this type. Use a commercially available tomato cage or a sturdy stake to support this plant, but place the support in the pot before planting, to prevent damaging the plant's roots. Tie the plant to the support at intervals, using soft ties.
Feed the plant regularly to keep it setting fruit for the entire season. The first grape tomatoes are usually ready to harvest about 75 days after planting, so start feeding plants once weekly when you see the first small, green fruits -- usually sometime in July, depending on your climate. Use a balanced, 20-20-20 formula, diluting it at a rate of 1/4 teaspoon per gallon of water, but also check your product label for additional directions. Wet the soil before feeding to avoid burning roots.
Grape tomatoes are susceptible to several fungal disorders; these are best prevented by keeping the pot in a well-ventilated area that's not crowded by other plants and by watering the plant at its base early in the day, helping keep foliage dry.
Several pests can also cause problems, including the green tomato hornworm caterpillar and the brown, striped potato beetle; handpick and destroy these. Aphids, tiny, yellowish, soft-bodied insects, and small whiteflies can also feed on and weaken the plant. Control these by spraying with insecticidal soap until the plant's dripping wet. Dilute the soap at a rate of 5 tablespoons per gallon of water, and repeat the spray as needed.