My Heirloom Tomatoes Rot on the Vine Before Ripening!

“I have planted heirloom tomatoes and they rot on the vine before they turn red. Why?” Question from Susan of Lexington, Kentucky

Answer: There are several reasons why this can happen, but the most common is a physiological disorder called blossom end rot. This is most likely your problem, especially if your plants look fine. You can see an example of this disorder in the photo. As tomatoes develop, the base of the fruits turn from brown at the green stage. As they turn red, the bases turn black. Look familiar?

Managing Blossom End Rot

Fortunately, this is a very easy disorder to manage. It is simply caused by a calcium deficiency, and big, old-fashioned heirloom tomatoes can be especially susceptible, especially if your soil is nutrient poor and low in calcium.

To get your soil where it needs to be, amend your soil with a quality amendment, like Black Gold Garden Soil with added fertilizer. This will enrich your soil with needed organic matter and nutrients. It also has a pH between 6.0 to 6.8, which is perfect for tomatoes. Next, feed your tomatoes with a fertilizer formulated just for tomatoes and then add extra calcium-rich bonemeal as an added precautionary measure.

Keep your tomatoes well fed and watered, and they should give you good fruit with no end rot. One caveat: Some older tomato varieties are really end-rot sensitive, and even with fertilization the first couple tomatoes of the season may show end rot, but the remaining fruits will not.



Plants are the lens Jessie views the world through because they’re all-sustaining. (“They feed, clothe, house and heal us. They produce the air we breathe and even make us smell pretty.”) She’s a garden writer and photographer with degrees in both horticulture and plant biology from Purdue and Michigan State Universities. Her degrees were bolstered by internships at Longwood Gardens and the American Horticultural Society. She has since worked for many horticultural institutions and companies and now manages communications for Sun Gro Horticulture, the parent company of Black Gold. Her joy is sharing all things green and lovely with her two daughters.

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