Why Are My Tomatoes Not Turning Red? What to Do

Do you have a tomato plant full of green tomato fruits with no sign of turning red? This can be quite a frustrating experience, especially when frost is fast approaching. So, why are tomatoes not turning red?

Tomato fruits won’t turn red when the temperatures are not conducive. Overfeeding and overwatering the plant can also delay the ripening of the fruits. The plant tends to use most of its energy on the growth of foliage at the expense of ripening the fruits.   

Let’s dive into why your tomatoes stay green when you expect them to be ripening.

1. Extreme Temperatures

Temperatures above 85 degrees Fahrenheit [29.4 degrees Celsius] are too hot for the tomatoes to ripen. According to the Cornell University Cooperative Extension, the optimum temperatures for ripening of tomatoes are 70 to 75 degrees Fahrenheit [21.1 to 23.9 degrees Celsius].

Tomato plants produce carotene and lycopene pigments that give the fruits a red or orange appearance. The plant is unable to produce these pigments under high temperatures.

On the other hand, cold temperatures that are below 50 degrees Fahrenheit [10 degrees Celsius] can also stop or slow the ripening process. It is common in areas that receive a cold and wet spring or a dry and cold summer.

Cold temperatures can also ruin the flavor of tomatoes. The sugars in the fruits may turn into starch.

2. Depends on Tomato Variety

There are many different tomato seed varieties in the market. Some of the varieties do not turn red when ripe. They may ripen to orange, pink, yellow, purple, and even green. So, you may be wrong to be waiting for a green tomato fruit variety to turn red.

So, when trying a new variety, make sure you know its maturity period and what ripe fruits look like. If the frost is approaching and your tomatoes are still green, then you may have chosen the wrong variety for your area.

Go for short-season varieties when you live in an area that experiences a short growing season. They mature fast and hence give the green fruits more time to increase in size and turn red before the temperature starts dropping.

Some of the best short-season varieties include Early Girl, Glacier, and Stupice. 

3. Excess Foliage

Tomato plants require a lot of energy to sustain the leaves, vines, and flowers. If the plant is using more energy on the foliage, it may be left with little energy to turn the green fruits red. To prevent this from happening, you are supposed to start pruning your plants early.

When the lower leaves start turning yellow, it is the first indication that your plants are ready for pruning. Use pruning shears to cut off suckers. Remove excess leaves and top the plant towards the end of the growing season.

Pruning aids the ripening of fruits by discouraging the plant from further blossoming. It concentrates the energy towards the ripening of fruits rather than producing more fruits. It also improves air circulation around the plant and hence decreases disease infections.

4. Overfeeding and Overwatering

Tomatoes may not ripen fast when the plant is overfed and overwatered. Tomato plants require enough nutrients and water to grow healthy and produce high yields. However, you are supposed to slow down on fertilizer and watering when the plant achieves the desired size.

Reducing watering to the point where a plant is slightly stressed can trigger ripening of the fruits. It typically stops the plant from producing new blossoms and directs the energy towards fruit ripening.

Practicing this trick can enhance ripening, especially when you are staying in a region that experiences shorter growing seasons

If your region is experiencing longer seasons, you may want to continue watering the plants with enough water to continue blossoming. 

How to Turn Green Tomatoes Red

Although you may not force a green tomato to turn red, there are various tips you can use to speed the process. They include:

1. Provide shade in hot temperatures

Temperatures that are above 85 degrees Fahrenheit [29.4 degrees Celsius] inhibit the plant from producing carotene and lycopene pigments. These pigments are responsible for the orange or red color of the tomatoes. 

Providing shade over your plants during the hot hours of the day can help to maintain the temperature within the optimal range.

2. Slow down on fertilizer and water

Tomato plants require plenty of nutrients and adequate water during the growth period. However, you are supposed to go slow on water and fertilizer after the blossom. Slight water and nutrient stress encourage the plant to ripen the existing tomatoes.

3. Pruning the excess leaves

Other than improving air circulation around the plant, pruning the excess leaves also helps to promote the ripening of the fruits. Older leaves use more energy from the plant than they produce. However, be sure not to over-prune the leaves. The fruits may be damaged by the sun.

4. Harvest tomatoes regularly

Harvest any fruit as soon as they start to show a change in color. It allows the other fruits to get larger as well as ripen faster. Allowing red fruits to overstay on the plant can delay the ripening of other tomatoes. It uses the energy that would have been used by the other fruit to ripen.

5. Topping the tomato plant

Topping the tomato plants refers to cutting off the bud of the main stem. It can be done towards the end of the season or when the plant reaches the ceiling of a greenhouse. It helps to stop the plant from wasting energy on growing new leaves and flowers. The energy is directed towards the ripening of the fruits

6. Cut off the suckers

Suckers are simply new plants that develop between each leaf and the main stem. They suck more energy from the plant that would have been used in the ripening of fruits. They can develop into new plants and can produce fruits when allowed to grow. Although the fruits will be smaller.

7. Remove some flowers

Remove all the blossoms that appear later in the summer. It takes a few months for pollinated blossoms to form fruit, enlarge, and get ripe. The frost may fall before the fruits get ripe. The plant may also direct more energy towards the new blossoms at the expense of ripening the already existing fruits.

8. Removing tiny tomatoes

Tiny tomatoes on the plant may not have enough time to mature. Removing them will help the other tomatoes to grow large and ripen faster.

9. Pruning the roots

Subjecting the plant to a slight stress triggers the ripening of the fruits. You simply use a shovel to cut the roots a few inches away from the plant. Pruning the roots also reduces the amount of water absorbed by the plant.

10. Keep the plants warm

Temperatures that are below 50 degrees Fahrenheit may also slow down the ripening process. If your plants are in pots, you can move them indoors. The optimum temperature for the ripening of tomatoes is 70 to 75 degrees Fahrenheit.

How Long Does it Take Tomatoes to Turn Red?

Generally, after the flowers are pollinated, it takes 6 to 8 weeks for the tomatoes to enlarge and start ripening. Tomato fruits ripen from June until the fall of the first frost. The warm and light conditions of summer are ideal for the ripening process. 

The ripening process slows down as winter approaches. Flowers and fruits that develop after September may not be able to ripen due to the frost.

When winter is fast approaching, you can help to fasten the ripening process by removing any remaining flowers and small tomatoes from the plant. The plant will channel its energy towards the ripening of the remaining fruits.

Tomatoes that are not fully ripe can be picked and stored in a kitchen cabinet to ripen fully. The best flavor is achieved when the tomatoes are left to ripen on the vine. It increases the acidity that turns starch into sugars, as well as softening the fruit.

Final thoughts

Red, juicy, and delicious tomatoes are the aim of any gardener. However, you may get some disappointments on the way when the green tomatoes fail to turn red. It is never too late; employing some of the tips above will help the green tomatoes to turn red. If you did not have time for the last-minute efforts, remember there is always next season.