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Why Aren't My Tomatoes Ripening?

Steve Reiners, Co-Team Leader, Cornell University
Eastern New York Commercial Horticulture

August 22, 2012

Why Aren't My Tomatoes Ripening?
With all of the hot weather we have experienced this summer, growers were expecting their tomatoes to ripen very quickly. Unfortunately, just the opposite is happening. Ripening seems very slow, almost like what we see in the autumn when temperatures are much cooler.

So what's happening? It takes six to eight weeks from the time of pollination until tomato fruit reach full maturity. The length of time depends on the variety grown and of course, the weather conditions. The       optimum temperature for ripening tomatoes is 70 to 75F. When temperatures exceed 85 to 90 F, the ripening process slows significantly or even stops. At these temperatures, lycopene and carotene, pigments responsible for giving the fruit their typical orange to red appearance cannot be produced. As a result, the fruit can stay in a mature green phase for quite some time.

Light conditions have very little to do with ripening. Tomatoes do not require light to ripen and in fact, fruit exposed to direct sunlight will heat to levels that inhibit pigment synthesis. Direct sun can also lead to sunscald of fruit. Do not remove leaves in an effort to ripen fruit. Also, soil fertility doesn't play much of a role. We do know that high levels of magnesium and low levels of potassium can lead to conditions like blotchy or uneven ripening or yellow shoulder disorder. But the slowness to ripen is not likely due to soil conditions and adding additional fertilizer will do nothing to quicken ripening.

If you absolutely cannot wait, some growers will remove fruit that are showing the first color changes.  These fruit, in the a mature green or later phase, could be stored at room temperature (70-75F) in the dark. A more enclosed environment would be best as ethylene gas, released from fruit as they ripen, will stimulate other fruit to ripen. If temperatures remain high outdoors, these picked fruit will ripen more quickly, perhaps by as much as five days. As far as flavor, the greener fruit should develop flavor and color similar to what you would get if field ripened. The key is picking them when they are showing the first signs of ripening (no earlier) and keeping them at room temperature. Do not refrigerate, as this will absolutely destroy their flavor.

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How to Take a Photo for Crop Diagnostics

With the current push to work remotely, using pictures to quickly address production questions has a lot of appeal and utility but the images must be of high quality.

In How to Take a Photo for Crop Diagnostics, readers will learn:
  • What makes a high quality image?
  • Things you should know
  • Different problems need different images
  • Steps for taking a high quality image
  • Pro tips
...Plus there a several side-by-side comparisons of poor quality photos versus high quality images with tips on what changes the photographer made to take the better photo. 

Cornell Commercial Vegetable Guidelines Available

The 2020 Cornell Integrated Crop and Pest Management Guidelines for Commercial Vegetable Production are now available!

Written by Cornell University specialists, this publication is designed to offer producers, seed and chemical dealers, and crop consultants practical information on growing and managing vegetable crops in New York State. Topics include general culture, nutrient management, transplant production, postharvest handling, organic production, and managing common vegetable crop pest concerns. A preview of the Vegetable Guidelines can be seen online.

Highlighted changes in the 2020 Vegetable Guidelines include: 
  • Updated pesticide options for economically important vegetable crop pests.
  • Completely revised weed management chapter.
  • Updated online crop and pest management resources.
Cornell Crop and Pest Management Guidelines are available as a print copy ($41), online-only access ($41), or a package combining print and online access ($57.50). Shipping charges will be added to your order. Cornell Guidelines can be obtained through many local Cornell Cooperative Extension offices, or from The Cornell Store at Cornell University or call (844) 688-7620.


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