Tomato Questions & Answers

May 5, 2007 Article

by David Rodriguez

The Bexar County Master Gardener Volunteers are a trained and yearly recertified educational hand of Texas Cooperative Extension. The Master Gardeners help man the Horticulture Extension office ‘Hotline’ at 210-467-6575, Monday-Friday from 8:00-5:00 PM. Tomato questions have been pouring in these last few days. Here are some of the Tomato questions with helpful answers.

1) Question: How often should tomatoes be fertilized?

Answer: It is necessary to fertilize the garden before planting tomatoes at a rate of half a pound of a synthetic 19-5-9, 50% slow release nitrogen per every 10 linear row feet. Apply the fertilizer again when fruit first sets. From that point on, an additional fertilization (side dress) every week to 10 days is recommended. Plants grown on sandy soils should be fertilized more frequently than those grown on heavy clay soils. A general side dress fertilizer recommendation is one-to-two tablespoons of 19-5-9, 50% slow release nitrogen scattered around the plant and worked into the soil. Upon application completion, thoroughly water in the fertilizer. If an organic analysis is preferred, follow the same application times and procedures, but double or triple the rates. A 4-2-3 or a 6-2-2 analysis works well.

2) Question: Should tomato plants be staked, caged, or left unsupported?

Answer: Tomatoes should be supported. Whether you cage or stake them is personal preference. Regardless of the method, plants with foliage and fruit supported off the ground will produce more than unsupported plants. Caging has several advantages. It involves less work than staking. Once the cage is placed over the plant there is no further manipulation of the plant – – no pruning, no tying. The fruit are simply harvested as they ripen. In many areas, staking and pruning of the plant to a single or multiple stem results in sunburn, when the developing fruit is exposed to excessive sunlight. Other advantages of caging over staking include protection of fruit from bird damage by more vigorous foliage cover and less fruit rot. Caged tomato vines produce more fruit of a smaller size, but staked and tied plants produce less fruit which mature earlier yet are larger.

3) Question: My tomato plants look great. They are dark green, vigorous, and healthy. However, flowers are not forming any fruit. What is the problem?

Answer: Several conditions can cause tomatoes to not set fruit. Too much nitrogen fertilizer, nighttime temperatures over 70 degrees F., low temperatures below 50 degrees F., irregular watering, insects such as thrips or planting the wrong variety may result in poor fruit set. Any of these conditions can cause poor fruit set, but combinations can cause failures. If Horticulture Extension recommended varieties are used, the main reason tomato plants do not set fruit is because they are not planted where they can receive 8-10 hours of direct sunlight daily. Any less direct sunlight will result in a spindly growing, nonproductive plant with healthy foliage. For a complete listing of Extension Horticulture tomato and vegetable recommendations for Central and South Texas, please visit this link at:

Remember, Learn and Have Fun! And as always, do not hesitate to contact the Master Gardener Extension Horticulture ‘Hotline’ at 210-467-6575 for any other tomato or gardening and landscape questions.

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