4 Reasons Why Your Tomatoes Aren't Turning Red

Tomatoes not turning red? This can be a frustrating problem, especially after you've kept on top of tomato plant diseases such as blight and blossom-end rot, and made sure to regularly water and fertilize your tomato plants. So what's going on when your developing tomato fruits stubbornly stay green and refuse to ripen? Here's what may be slowing down ripening, and how to help your tomatoes turn red.

Why Tomatoes Aren't Ripening

Among the most common reasons why your tomatoes are not turning red are high temperatures, too much nitrogen in the soil, too many fruits on one plant, and the type of tomato you're growing. Here's how to figure out which issue is the culprit, and what you can do about it.

1. Temperature

Usually, weather is the most likely reason that your tomatoes aren't ripening on the plant. The best temperature range for ripening green tomatoes is between 68 and 77°F. Your tomatoes can still ripen outside that range, but the process will be slower. When temperatures reach over 85°F, the plants won't produce lycopene and carotene, which are the two pigments responsible for ripe tomato color.

If your area has hot temperatures for an extended period of time, the ripening process might stop and you could end up with tomatoes that are yellowish-green or orange. There's not much you can do when the weather is too hot except wait for temperatures to go back down, at which point the ripening process will resume.

2. Too Much Nitrogen

It happens to gardeners with the best intentions, but it's possible to overfertilize your tomatoes. In particular, if you use a product high in nitrogen, this can spur your plants to divert energy to producing leaves instead of getting on with the business of ripening existing fruit. Once your plants start setting fruit, cut back on fertilizing. Typically, you'll only need to fertilize tomato plants two or three times during the season.

3. Too Many Fruits

If temperatures are not too hot and your plants aren't overfertilized, yet your tomatoes still seem to be taking forever to turn red, it could be your plant has too many fruits developing at the same time. Hard as it may feel to do, remove about a fourth of the total number of fruits. This will help your plant concentrate its finite energy and resources on ripening just the fruit that's left.

4. Type of Tomato

Sometimes it may seem like a tomato fruit is taking too long to ripen, but that just may be that type of tomato's natural speed. A cherry tomato will generally take fewer days to fully ripen that a huge heirloom fruit. It could be that a little patience is all that's needed.

How to Ripen Green Tomatoes After Harvesting

As fall arrives and temperatures consistently stay below 50°F, your tomatoes won't ripen anymore on the vine. As long as the green tomatoes have started to turn color a bit (you should see just a touch of color at the blossom end of the fruit) and are a little soft to the touch, there's a chance they'll ripen indoors.

Place your harvested tomatoes in an area that's 60 to 65°F (your pantry or basement might be perfect). Tomatoes don't necessarily need sun to ripen, so you can try placing them in a paper bag with an apple or a banana to speed the ripening process along. These fruits give off a lot of ethylene gas, which will help speed up the ripening process for your tomatoes.

Finally, you can try uprooting whole plants and hanging them upside down indoors. Sometimes, the tomatoes can ripen on the vine as the plant dies. Just be sure to get as much soil off the roots as possible before bringing the plant inside. And if you're growing tomatoes in containers, you can also move the whole plant indoors in its pot and set it in a sunny spot until the last fruits finish ripening.