“How are your tomatoes doing this year?” is a common summer conversation starter among gardeners. It is a ritual for 86 percent of home gardeners to grow tomatoes in vegetable gardens or containers.
Tomatoes are easy to grow—unless insect pests, disease, heat, cold, drought or excess rains interfere.
There are thousands of tomato varieties. Heirlooms are known for flavor and diversity, but at the cost of disease and pest resistance. Hybrids, however, are typically vigorous growers that are heavier producers of fruit and more resistant to disease.
To select disease resistant hybrids look for the following letters after the cultivar name: F, FF, and FFF – fusarium wilt, V – verticillium wilt, A – Alternaria fungus, St – Stemphylium (stem leaf spot), TSWV – tomato spotted wilt virus, N - nematodes and T - tobacco virus.
The terms determinate and indeterminate are important to know when choosing a variety. Determinate tomatoes grow in bush form to about four feet high. Plants bloom and fruit only one time. An indeterminate tomato grows with a vining habit and produces fruit until frost.
Tomatoes grow best in well drained acidic soil, pH 5.8 – 6.5. If raising them in a container use good potting soil and a fertilizer formulated for tomatoes. When planting them directly in the garden know your soil first. Have the soil tested and correct the nutrients and pH if necessary.
Install a tomato cage or support when you plant or soon after, otherwise the plant will quickly become too heavy and unwieldy to adequately prop up. It’s important to keep the fruit off the ground to prevent rot.
Tomatoes are heavy feeders and need to be fertilized regularly. A 5-10-5 slow release fertilizer is a good option. Compost and worm castings are beneficial soil amendments in addition.
The plants are heavy drinkers but need even moisture. Avoid keeping them too wet but don’t wait until they dry out to water them.
Give tomatoes at least six hours of sun per day.
Damping off is a fungal disease that causes seedlings to collapse and die, and transplants to wilt and die soon after planting. You will see a water-soaked area on the lower stem just above the soil. To prevent the problem start seeds in sterile media. Don’t overwater starts and avoid nitrogen fertilizer before seedlings have produced their first true leaves. Damping off is frequently associated with starting seeds too early in the spring.
Fusarium wilt is a fungal disease that causes young plants to wilt and die. Prevent it by using uninfected soil. The disease may also result from infected transplants.
Do not plant tomatoes in the same garden spot in back-to-back years or in the same location where peppers and eggplants grew the previous year. These vegetables are hosts to the same pests and diseases. Don’t recycle potting soil among these vegetables.
Blossom end rot presents itself on the blossom end of the fruit with a water-soaked spot that quickly turns black. It usually results from uneven moisture and calcium deficiency. Over fertilizing with nitrogen and potassium depresses the uptake of calcium thereby encouraging blossom end rot.
Leaf roll is a physical condition caused by too much water.
Growth cracks develop in combination with drought followed by heavy watering, then rapid growth while fruit is ripening.
No fruit set or poor fruit set often results from tomatoes’ sensitivity to temperatures—above 90 degrees in daytime or below 55 degrees nighttime. Insufficient water, inadequate sun and over fertilizing with nitrogen can also cause blossoms to fall off before the plant sets fruit. Tomatoes are self-pollenating; wind, bees or wasps usually do the job. However, if a plant lives in a sheltered area it may need some help with a good shake to loosen the pollen.
Tomatoes need to be monitored for insect pests. Control aphids, spider mites, flea beetles, white flies with insecticidal soap. Use horticultural oil for leaf-footed and stink bugs, flea beetles, white flies, spider mites. Treat fruit worms, hornworms and thrips with spinosad.
Clemson’s Home & Garden Information Center website offers more detailed information and excellent pictures of tomato problems. Google/search hgic 1323 Tomato, hgic Tomato Diseases and Disorders and hgic 2218 Tomato Insect Pests to access the pages.
Reach Debbie Menchek, a Clemson Master Gardener, at firstname.lastname@example.org.