The Q&A Archives: Controlling Blossom End Rot

Question: I have several San Marzano tomatoes in a pot, and there are about 20 tomatoes on the plants. Five or 6 of them have blossom end rot. What can I do about this? Also, I am growing two beefsteak tomatoes and they have grown to about 4 1/2 feet and have many blooms but have not yet set any fruit. The overnight temps here in Glendale are about 55-60 degrees lately. I fertilize with Miracle Gro for Tomatoes. What am I doing wrong? Cheryl Murphy Glendale, CA

Answer: Tomatoes setting fruit! I'm jealous! I haven't even planted my peas yet here in Northern Vermont! Blossom end rot is a symptom of calcium deficiency that arises when soil gets very dry during hot, sunny weather, so it is a common problem in container-grown tomatoes. Water plants well and add some kind of mulch (shredded straw or grass clippings) to the soil surface to maintain soil moisture. Pick off the affected fruit, and mist the leaves of the plants with a kelp or seaweed based foliar fertilizer (if you can't find it locally, it's available from Gardener's Supply Co., or 800-863-1700). This should give them the nutrients they need quickly to recover and produce healthy fruit. The beefsteak variety sounds like it's getting too much nitrogen fertilizer, which stimulates lush, green growth at the expense of fruit. Since your fertilzer is designed for tomatoes, make sure you are applying it at the correct rate. You can substitute the fertilizer I mentioned above, too and see how that serves.

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