Tomatoes are a popular garden fruit, and waiting for them to change from green to red tests a gardener’s patience. The shift to a mature color marks the final stage of ripening, where the fruit softens, develops flavor, and acquires its final hue. This transformation signals the tomato is ready for picking. The time it takes is variable, but typically, a full-sized green tomato takes about 20 to 30 days to complete this color change under favorable conditions.
The Standard Timeline for Ripening
The ripening journey begins after the tomato reaches its full mature size while still completely green, a stage known as “mature green.” The total time from the flower blooming to a fully ripened fruit can be six to eight weeks, but the final color change is a concentrated period within that timeline.
The color change starts at the “breaker stage,” when a blush of color first appears, usually near the blossom end. This indicates the fruit has begun producing the ripening agent, the plant hormone ethylene. Once a tomato reaches this stage, it is physiologically mature and can be harvested to finish ripening off the vine without flavor loss.
From the breaker stage, the fruit shifts from green to an almost yellow hue before the red pigment, lycopene, fully develops. For most varieties, the transition from this first blush of color to a fully red tomato generally takes three to five weeks on the vine. Smaller types, like cherry tomatoes, ripen more quickly, while larger beefsteak varieties take longer.
Key Environmental Influences on Color Change
While the fruit’s internal clock determines the timeline, external environmental conditions significantly influence the speed of color change. The most important factor for efficient ripening is temperature, with an optimal range for red pigment conversion occurring between 68°F and 77°F. Temperatures consistently cooler than this range, especially below 60°F, slow the ripening process considerably.
Consistent soil moisture supports healthy development, although overwatering can be detrimental. Proper watering ensures healthy vines, allowing the plant to direct energy toward fruit development and ripening. Too much nitrogen, however, slows ripening because it encourages the plant to focus resources on producing leafy green foliage instead of fruit.
Direct sunlight is not necessary for red color development; heat is more important than light for ripening. Tomatoes fully exposed to direct, hot sunlight can reach temperatures that inhibit the color-producing mechanism. Ideal ripening conditions are warm but not excessively hot, and the plant’s foliage naturally provides the necessary shade.
Why Tomatoes Stop Turning Red
A sudden stall in the color change is often a sign that the temperature has exceeded the fruit’s physiological tolerance for ripening. When temperatures consistently rise above 85°F to 90°F, the process can slow down or stop altogether. This failure is tied directly to the production of lycopene, the carotenoid pigment responsible for the red color.
At these high temperatures, the enzymes needed to synthesize lycopene become inactive. The fruit may still produce carotene, a more heat-tolerant, yellow-orange pigment, resulting in tomatoes that look yellow or orange instead of red, a condition often called “green shoulders.” This heat stress also inhibits the production of ethylene, the plant hormone that triggers ripening.
If tomatoes are stalled in the green or breaker stage due to excessive heat or early frost, they can be picked and ripened indoors. Mature green or blushing fruit should be placed in a controlled, room-temperature environment, ideally between 60°F and 75°F, where ripening will continue. Placing them in an enclosed space, such as a paper bag with an apple or banana, concentrates the naturally released ethylene gas, stimulating faster and more uniform ripening.