By Calvin Finch, Conservation Division, Manager, Water Resources & Conservation Dept., SAWS, and Horticulturist

TOMATOES

Tomatoes are the favorite vegetables to grow in San Antonio. They are relatively easy to grow and can be very productive. You can grow tomatoes in a container or a raised bed.           

Tomatoes require full sun to produce to their full potential. Full sun means at least eight hours of sun through the course of a day. A little shade in late afternoon is not a problem, but planting at the base of a tree or on the West or East Side of the house is not going to make it.A tomato in a 5-gallon container can be successful if you water every day and apply soluble (dissolves in water) fertilizer once per week with the water. Fill the container with good quality potting soil and a cup of osmocote (or similar) fertilizer. Osmocote is a slow release granular fertilizer that supplements the soluble fertilizer. A larger container like a half whiskey barrel is even better than a 5-gallon container.

            For a container, select a tomato variety that does not get huge. The indeterminate cherry tomatoes are not good choices, but Jerry Parsons’ ‘Dwarf Cherry Surprise’ or ‘Surefire’ work well. Even ‘Merced’ is successful in a container. Most nurseries carry ‘Patio’ tomatoes, bred specifically for containers. It is a very attractive plant with dark green foliage and a disciplined growth habit, but the fruit is not in the league with the other recommended selections.

The varieties recommended for a raised bed in San Antonio are Merced, Celebrity, Heatwave, Sun Master, Carnival, Bingo, or Whirlaway. All are determinate or semi-determinate which means they form relatively small plants and then set fruit over a short season. This is a desirable trait for a South Texas tomato because there are two windows of suitable fruit-setting weather April through May and September through October. To take advantage of the windows we plant two crops of quick maturing varieties. Now is the time to plant the spring crop. It will bloom and set fruit to be harvested in June and early July. After the harvest the plants are discarded to avoid being reservoirs for spider mites and disease.

Plant your tomatoes at least 3-feet apart. I plant 3 in a row in an 8-foot raised bed. After the transplants are placed, surround them with a tomato cage at least 3 feet tall. The cage keeps the fruit off of the ground.

Mulch over the root system with leaves or other organic material. I like leaves because they decompose quickly and can be incorporated into the soil. Mulch is important because it reduces weeds and conserves water. If your soil dries out between waterings, blossom end rot results. Blossom end rot looks like a fungus disease (black flattened tomato bottoms), but it is a calcium deficiency as a result of an interruption of calcium flow in the transpiration stream from the soil. The transpiration stream is water flowing from the roots and out the leaf surfaces.

            Drip irrigation is the most efficient way to water tomatoes. A 2—3 hour application every two days when the plant is full of fruit is necessary.

            Fertilize tomatoes in raised beds with slow release lawn fertilizer. A cup spread over each 8-feet of row before planting, and one cup per plant every three weeks until the fruit sets is recommended.

            Organic gardeners can ward off insects and diseases by sealing the plants in Grow-Web or other agricultural fiber until the leaves reach the cage. Neem oil products are also used. Bt applied every week will keep most caterpillars in control. Pinworms and hornworms are especially destructive.

Malathion and carbaryl are manufactured insecticides labeled for vegetables. Kelthane kills spider mites. Chlorothalonil applied weekly will ward off  daily blight but most gardeners do without. Most crops will mature before fungus destroys the plants.