The Q&A Archives: Ripening and rotting tomatoes

Question: First time tomato planter has a plan growing in a pot. As the tomatoe ripens, all seems fine on the top, but underneath it is starting to rot. I shows a brownish whitish patch. What can I do or am I doing wrong?

Answer: Your plan is a good one! Most tomatoes will adapt to growing in containers as long as you keep them watered and in full sunshine. What you describe sounds like a common disease called blossom end rot. This is a physiological problem related to the availability of calcium in the developing fruit. It happens most often with the first cluster of fruit on a plant when the rapidly developing plant cannot keep the supply of calcium coming fast enough to the new fruits. There are many factors that affect the movement of calcium through tomato plants, but the most important is water. If the plant ever wilts, even for a few minutes, there is a risk of this condition developing.

The first evidence of blossom end rot consists of a brown or watersoaked discoloration near the blossom end (opposite the stem end) of the fruit. The discolored area enlarges and darkens until it covers 1/3 to 1/2 the surface of the fruit in severe cases. As the spots increase in size, the tissue becomes shrunken and the area becomes flattened or concave. The skin of affected fruit becomes black and leathery in appearance.

Tomatoes affected by blossom end rot grow slowly and often ripen prematurely. Blossom end rot is most frequently observed on fruit that is 1/2 to 2/3 its mature size.

Since blossom end rot is a physiological problem, caused by inconsistent soil moisture and the inability of the roots to take up needed calcium, you can control the problem by maintaining a uniform supply of soil moisture, and avoiding the use of excessive amounts of ammonia forms of nitrogen, which reduce calcium uptake. Instead, use light applications of fertilizers high in superphosphate, which will aid in reducing blossom end rot.

Foliar applications of calcium can be used but they are not always effective. They are available in garden centers.

Hope this answers all your questions!

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