Week of February 25, 2002

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

“POTTING UP” TOMATOES

            Do you believe homegrown tomatoes are superior to the store bought? Would you like to maximize tomato production in your garden and maybe even get the first tomato of the season? If so, it is time for you to “pot up” your tomatoes.

“Potting up” is a tactic of putting tomato transplants into containers to maximize growth but still be able to protect them from cold weather until early April when the weather stabilizes enough to place them in the garden.

            Obtain some one-gallon containers. The black plastic pots that nurseries use work fine. Fill them with a good quality potting soil enriched with one-half cup of osmocote. Plant the transplant into the pot and water it in.

The key to success in “potting up” is to find a sunny, sheltered spot where the tomato can benefit by the light and warmth without being subjected to wind. A greenhouse with ventilation is perfect. It is also necessary to watch the forecasts and move the containers to shelter when temperatures are going to be below 40 degrees F. Forty degrees is selected because the tomato will “harden off” at low temperatures. It won’t die but it will chemically switch from a maximum growth mode to a survival mode. The whole idea of “potting up” is to keep the plant growing at a maximum rate until we reach the window in our weather where it is warm enough but not too warm for tomato production.

            Do not let the tomatoes dry out either, that is another way to stop growth. Some gardeners supplement the osmocote with a soluble fertilizer once every week when they water. A soluble fertilizer is one like Peters, Schultze or Miracle-Gro that dissolves in water.

If you do everything right the tomatoes should have a well-developed root system and may even have started blooming when they go in the garden about April 1. If the weather is suitable you could try a few of the plants in the garden early and also save a few spares until April 15 to make sure a late spell of bad weather does not hurt the tomatoes in the garden.

To make sure your “potted up” tomatoes have optimum fruit production conditions in the garden, select a site in full sun, mulch, and use drip irrigation. My favorite mulch for the vegetable garden is live oak leaves. Fertilize tomatoes in the garden every four weeks with slow release lawn fertilizer (one cup per plant away from the stem over the root system)

            San Antonio is a two-growing season (spring and fall) gardening area. The determinate tomato varieties that reach a moderate size and set their fruit over a short season do better than the indeterminate tomato varieties that they use up North. Select Merced, Celebrity, Surefire, Heatwave, Sun Master, Carnival, Bingo, and Whirlaway for reliable production. Determinate varieties like Big Boy, Beefsteak, and Better Girl make large plants but are not reliable producers in San Antonio.

            We want to pull and discard tomato plants at the end of June before they are loaded with spider mites and disease. Plant another crop in late July or early August. This two-season technique has proven to be the most effective way to maximize tomato production in the San Antonio area. “Potting up” is not necessary but improves your chances of an early large crop of spring tomatoes.