Anticipation is likely one of the reasons it seems to take forever for your tomatoes to turn red. There are dozens of different kinds of tomatoes, and they’re pretty easy to grow. But what makes them so popular in home gardens across the US is their fresh, juicy taste and texture.
It can feel like you’re waiting forever for them to turn the right shade of red, but there are other, less emotional reasons why your tomatoes are still green. If your tomatoes aren’t turning red, here are some of the most common reasons and what you can do to make them ripen faster:
My Tomatoes Aren’t Turning Red – Here’s Why and What To Do
As a tomato gardener nothing is more frustrating than harvesting unripe, green tomatoes at the end of the season. After months of careful tending watering, staking, and fertilizing, you expect to enjoy big, red, juicy tomatoes all summer long. But sometimes, your tomatoes just don’t seem to ripen fully. If you’re wondering “why aren’t my tomatoes turning red?”, you’re not alone. Read on to learn the most common causes of green tomatoes and get helpful tips to encourage ripening.
The Most Common Reasons for Green Tomatoes
After consulting expert gardeners and researching trusted gardening resources like Martha Stewart and Better Homes and Gardens, I’ve learned the top factors that prevent tomato ripening are:
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Temperature – Tomatoes need warm daily temperatures between 66-78°F to properly ripen. Temperatures consistently above 85°F or below 60°F will halt ripening.
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Excess Nitrogen – Too much nitrogen fertilizer leads to leafy growth instead of fruit production. Go easy on high-nitrogen fertilizers when tomatoes start setting fruit.
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Overloading Plants – Plants allowed to set and grow too many tomatoes at once don’t have resources to ripen them all. Pruning overloaded plants helps.
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Varietal Traits – Some tomatoes naturally take longer to ripen or stay partially green when ripe based on their genetics. Check seed packets.
Simple Ways to Help Your Tomatoes Ripen
Luckily, there are several easy things you can try to help coax your green tomatoes to ripen fully:
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Move containers to warmer areas and provide shade cloth or shade structures to keep temperatures ideal.
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Cut back on high-nitrogen fertilizer and instead use phosphorus-rich solutions.
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Prune plants by removing suckers and pinching off new growth to redirect energy to existing fruit.
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Thin fruits so there is ample sunlight and nutrients distributed among them.
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Harvest mature green fruits and ripen indoors by storing with ethylene-producing fruits like apples.
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Allow frost-tender plants to continue ripening indoors in a sunny window until finished.
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Be patient with slower-ripening varieties like heirlooms; they need time to develop flavor.
Temperature Too Hot or Too Cold
One of the most important things for tomatoes to ripen is the temperature. If it’s a few degrees too hot or too cold, the process stops or the tomatoes don’t ripen at all. The ideal temperature tomatoes need to acquire their red color is 68 to 77 degrees F. At 85 degrees, the plant stops making lycopene, so it leaves big green fruits on the vine until the temperature drops to a better level. Temperatures consistently below 60 degrees F. also inhibit ripening.
When fruits are fully ripe and have a slight blush, they can be picked and brought inside to finish ripening. They do not need to sit in a sunny window as long as the correct temperature is provided.
Even though it might seem counterintuitive, too much sun exposure can slow down ripening. For ripening, heat is more important than light, and too much bright, hot, direct sunlight can raise temperatures so high that they stop the production of lycopene. Pruning leaves away from mature tomatoes to give them more sun exposure can also cause sunscald and cracking.
In order for tomato plants to keep growing fruit, the vines need about an inch and a half of water every week. But once the fruits are fully grown, they ripen faster if the watering is cut back or stopped altogether. Less water stresses the tomato plant and sends it into survival mode. The plant will focus energy into producing viable seed, which helps accelerate ripening.
Tomatoes require a lot of nutrients and micronutrients throughout the growing season. Phosphorous and potassium are particularly important for the production and synthesis of lycopene in the fruits. Insufficient amounts can cause slow or uneven ripening. When the first small fruits show up on the plant, feed it with a fertilizer that has more phosphorous, like NPK 5-10-5.
What Makes Tomatoes Turn Red?
The energy that makes a tomato ripen comes less from the plant and more from changes inside the fruit once it reaches its full green size. When the fruit’s nutrition and environment are just right, it releases a natural hormone called ethylene. This hormone causes lycopene to be made. Lycopene is the pigment responsible for the orange and red colors in fruits like apples and tomatoes.
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