Primetime Newspapers
By Calvin R. Finch, PhD,
SAWS Water Resources Director, and Horticulturist
Week of February 20, 2006 
“Potting Up Tomatoes”

            Have you ever wondered how the gardeners who harvest the first tomato beat everyone else?  The usual trick is to “pot up” tomatoes now and then plant the result of the “potting up” into the vegetable garden about April 1 when the soil and air temperatures have warmed up enough to support tomato plant growth and fruit setting.

 

            Area nurseries have a good selection of tomatoes.  I have seen Solar Fire, SunPride, Celebrity, Carnival, SunMaster, 444, and Bingo.  They are all semi-determinate, which means they grow their foliage and then set their fruit in relatively distinct stages over a short season.  Such a plant works best for a climate like San Antonio where we have a short period of mild weather in late spring (and again in the autumn) when conditions are suitable for tomatoes.  The indeterminate varieties like Better Boy, Better Girl, and Beefmaster produce fruit and grow foliage together over a long season.  In San Antonio the result is usually huge plants and two or three big fruit.  I do not know about you, but I would rather have fruit than foliage! 

 

            To “pot up” your transplants, fill a one to three gallon black plastic container with a high quality potting soil.  Enrich the potting soil with a slow release granular fertilizer made especially for containers.  Be generous with the fertilizer, tomatoes are heavy feeders if you want maximum fruit production.  Place the transplants in the container.  They can be planted deeply; tomatoes are one of the few plants that can tolerate deep planting.  Roots will form along the whole stem.  This is especially important if you transplants are leggy or top heavy. 

 

            The goal of the “potting up” activity is to maintain the fast growth rate established at the nursery.  Place the potted up tomato in full sun in a location out of the wind.  The wind can injure foliage and reduce tomato growth.  A greenhouse is ideal, but many locations on the patio or the south side of the house also work well. 

 

            It is important to keep the tomatoes well watered.  Watering every other day is not too often.  The high quality potting soils are very well drained so they usually will not become soggy.  Reduce watering when the weather is overcast and/or cool.

 

            If the plant is subjected to more than a few hours of sub 40°F temperatures it will “harden off.”  To “harden off” means that the plant is reorganizing its chemistry to survive rather than to grow.  You will recognize it if the plant stops growing and you see some purplish coloring.  “Hardening off” is what will happen if you plant the tomatoes directly into the garden before April 1. 

 

            To maintain the tomato transplant in a growing state move it to shelter when temperatures below 40°F are forecast.  That may mean putting the pots in the house on cold evenings.

 

            If you do everything as described your “potted up” plants will be quite large and may even begin blooming by April when they can be transplanted to the vegetable garden. 

 

            Refertilize the newly planted tomato with one cup of slow release lawn fertilizer (19-5-9 is good), and then mulch with live oak leaves or another material. Irrigate every two or three days.  Drip irrigation is the best method.  Six to eight weeks later you will be harvesting tomatoes just like those folks shown holding the first tomato in the newspaper. 

           

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

- 2 -