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Tomatoes-with-Black-Bottoms-THUMB.jpg

Tomatoes with Black Bottoms

I've been growing tomatoes out of approximately 20-gallon pots for the last couple of years. I've been using the same potting mix. Last year the tomatoes were black on the bottoms - sort of like they were rotting. I took a tomato to a garden center. They said the soil was calcium deficient. I used a calcium spray they recommended - this did not help. Do I need to replace all the soil or can I add something to the soil to correct this problem - some type of fertilizer?

The problem is blossom end rot. This is a common problem in container gardens as well as in-ground gardens when plants experience a moisture imbalance. When plants go through periods of excess and/or insufficient moisture they are unable to absorb needed nutrients like calcium. Adding more calcium is not needed with most potting mixes or gardens growing in regions with plenty of calcium in the soil. Your local Extension service will know if this is an issue in your area. I would start by correcting your watering. This usually eliminates the problem. Make sure to water your containers thoroughly and often enough to keep the soil slightly moist. The good news, the problem usually corrects itself after the first set of fruit. Consider changing the potting soil in your containers this season. I change the soil in my containers every year. I recycle it in my compost pile and eventually into my garden. I do not want to increase the risk of disease or insect problems by reusing the soil the following year.

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