The Q&A Archives: Container Tomatoes Doing Poorly

Question: My Mother has health problems and is unable to garden herself. As a result I have been making containers for her and dropping them off at her house. Last year I put a Patio Tomatoe in a decorative container with Container mix soil. But she only got 6 tomatoes. She waters thoroghtly every day and uses liquid plant food as directed. They are also in full sun. This year I decide to try a standard Beef Steak Tomatoe. Today I saw them and they looked sad. Only 4 tomatoes and they were very small and the plants themselves were small too. Very different from my own in my garden which are about 5 feet tall with bright green leaves. My mother's plants have leaves that are small with a black tinge to them and you can see the veins. She still loves them but I feel like something is terribly wrong. She should have the best tomatoes not the worst. Any suggestions for next year?

Answer: It can be difficult to grow tomatoes in containers, in part because the roots are constricted and in part because the soil may be imbalanced in one way or another. For best results, try to use a variety that is characterized as doing well in containers, and use as large a container as possible. A five gallon bucket would be the minimum size for a standard tomato, with a half barrrel planter being better. Next, use a good quality potting soil. A soilless mix is often preferred because it is relatively sterile. It also holds both water and air so it can be kept moist yet well drained. Next, careful attention to fertility can make a big difference. You might use a water soluble fertilizer formulated specifically for tomatoes applied according to the label instructions along with an occasional top dressing of compost. An occasional application of a seaweed based water soluble fertilizer with many micronutrients can also help. Finally, make sure you grow disease resistant varieties; avoid wetting the foliage during routine watering; if they are blooming but not setting fruit there may be a pollination problem. If this is the case, give the plant a good shake about once a day or so and/or try one of the tomato blossom set sprays available at garden centers.

Last but not least, the symptoms you are describing sound like a nutrient problem of some sort. For instance, a nitrogen deficiency can cause small plants and purple veining, a phosphorus deficiency can cause a purple tinge and slow fruit set, too. A pH that is too high (above about 6.5) can cause yellowing and show the veins as can an iron deficiency. You might try some foliar applications of a fertilizer formulated for acid loving plants and with micronutrients; also as a tonic and to combat what may be an alkaline pH, try two or three foliar applications of Epsom salts (Mix in water at a rate of a Tablespoon epsom salts to a gallon of water) about a week apart and see if that helps. Also be sure that the plants are being kept evenly moist but not overwatered.

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