Why Aren't My Tomatoes Ripening? - Cornell Vegetable Program

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Why Aren't My Tomatoes Ripening?

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August 22, 2012With 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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Virtual Asparagus School

March 17, 2026

Join us to dive deep on growing asparagus! Bringing together experts from the Cornell Vegetable Program, Michigan State University, OMAFA (Ontario Ministry of Agriculture, Food, and Agribusiness), and industry, featuring a panel of growers.

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Postharvest Water Management, Sanitation, and Traceability Workshop

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Cornell University personnel from the National GAPs Program and the Produce Safety Alliance are presenting a workshop on postharvest water management, sanitation, and traceability. This workshop will include a mix of short talks and hands-on activities to provide attendees with applied experience with sanitation, postharvest water, and traceability topics. 2.75 NYSDEC CEU's in categories 10, 1a, and 23 available.

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March 20, 2026Geneva, NY

The Cutting Event will be held in the morning, followed by lunch, and the NYS Dry Bean Meeting in the afternoon. DEC recertification credits available for the NYS Dry Bean Meeting portion of the day: 2.0 in categories 1a, 10, 21, and 23.

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Cornell Crop and Pest Management Guidelines Paused

From Cornell IPM:Highlighting its commitment to quality and long-term sustainability, Cornell Integrated Pest Management's Pesticide Safety Education Program has announced a pause in production of the 2026 Cornell Crop and Pest Management Guidelines.Cornell IPM Director Alejandro Calixto said this temporary measure is the result of a comprehensive reimagining process facilitated by Illume Projects of Ithaca, which included end-user interviews, internal surveys and sales data analytics. "It became clear to us that we cannot continue producing the guidelines and fully restructure them at the same time," Calixto said. "By pausing production, we can dedicate all available resources and time to rebuilding the production process, ensuring that when we re-launch in 2027, the guidelines will reflect a modernized approach built around the grower and other user experience."A series of annually updated reference manuals produced by Cornell IPM and the College of Agriculture and Life Sciences (CALS), the Cornell Crop and Pest Management Guidelines are widely used by farmers, agronomists, crop consultants and extension educators in New York and throughout the Northeast. They include information about current IPM recommendations, pesticide options, cultural practices, nutrient management, disease, insect and weed identification and resistance-management strategies.Calixto and Pesticide Safety Education Program Lead Mike Helms will spearhead efforts to restructure the guideline process over the next 12 months, with a goal of launching a more streamlined, user-friendly version in 2027.Limited copies of the 2025 guidelines remain available for purchase while supplies last through The Cornell Store. The 2026-2027 Greenhouse Guidelines will be available.For more information contact Helms at [email protected]. NEWSLETTER | CURRENT PROJECTS | IMPACT IN NY | SPONSORSHIP | RESOURCES | SITE MAP Pay Invoice / Make Donation Cornell is an equal opportunity employer. For more information click here. If you have a disability and are having trouble accessing information on this website or need materials in an alternate format, contact [email protected] for assistance. ©2026 by Cornell University. All Rights Reserved web design and development by dsd web works Cornell University