Q: We have a beautiful tomato plant on our porch. Three tomatoes have turned red and the bottoms were all rotted. What are we doing wrong? When it wilts a bit, we give it water, but not too much.
— R.H., Racine, Wis.
A: It’s impossible to give a definite diagnosis without seeing the plant, but from your description, it sounds like your plant has blossom-end rot. It’s caused by a calcium deficiency in the fruit.
Drought can encourage the disease. Applying too much nitrogen fertilizer can also promote it. So can letting the soil bounce between wet and dry, so once the flowers have formed, I wouldn’t wait for signs of wilt to water the plant. Better to check the soil moisture by sticking your finger into the soil. You don’t want to overwater, but tomatoes need a good amount of water when they’re setting fruit.
Remove any affected tomatoes as soon as you notice evidence of the rot on them. You can’t save those tomatoes, but you may be able to prevent it on fruit that hasn’t yet formed by spraying the leaves with a calcium chloride solution. Look for calcium chloride at a garden center or hardware store, or you can buy calcium chloride products that are labeled as blossom-end rot treatments.
I assume your tomato is planted in a pot, but if it’s in the ground, I would also have the soil tested. It probably needs an application of lime to bring up the pH level, but testing is the only way to tell for sure what your soil needs.
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