"Blossom-End Rot Affects Tomato Fruit"
Q. Hi, we have two three-foot, green, and healthy-looking 'Jetstar' tomato plants loaded with good-sized tomatoes growing in large pots on the deck. However, the tomatoes are turning black and rotting on the bottom. The two that had turned red looked great until we picked them and they too were black on the bottom. We would like to know what is causing this rot and if there is anything we can do about it before we lose all the tomatoes to it. We grew plants on the deck years ago and do not remember having this problem. Any help you can offer is greatly appreciated! Thank you.
A. The problem with your tomato fruit is called blossom-end rot. It's a pretty common disorder with tomato fruit and can also occur on pepper, squash, and watermelon. It can affect vegetables planted in the ground as well as those planted in containers and, just like you, I noticed blossom-end rot on some of my tomato fruits this year from plants I'm growing in containers. It affects the first fruits the worst.
As its name implies, blossom-end rot always occurs on the blossom end of the fruit which is the bottom. It starts at the bottom, but can affect up to half the fruit. At the bottom of the fruit you'll see a circular, depressed, waterlogged spot that gets bigger and turns brown to black. The area feels leathery. Sometimes mold appears on the rotted area. The unrotted part of the fruit can be eaten.
Blossom-end rot is caused by a calcium deficiency in the developing fruit. The calcium deficiency is a result of slowed growth and injured roots caused by any (or all) of the following five factors:
1. Severe shifts in soil moisture from extremely wet to extremely dry.
2. Fast plant growth early in the growing season that is followed by a long period of dry weather.
3. Too much rain that smothers the plants' root hairs.
4. Too many soil salts.
5. Weeding or cultivating too close to the plant that results in damaged roots.
The best way to prevent blossom-end rot is to maintain even soil moisture at all times. For container-grown tomatoes, don't let the pot dry severely between waterings. Use a balanced fertilizer throughout the season, such as Electra Plant Food and Electra Bloom Food, and avoid high-nitrogen fertilizers that cause rapid green, leafy growth. Make sure the pot has good drainage to prevent the roots from being smothered. For tomatoes growing in the ground, make sure the soil is well drained. Excess soil salts is a problem, especially for plants growing in containers. When watering, provide enough water so that it drains out the bottom of the pot. This will help leach out any built-up soil salts. When weeding or cultivating near the plants, do not go deeper than one inch and stay a foot away from the plant with any cultivating tools. This will prevent damaging the plant's roots.
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