5 Reasons Tomatoes Are Not Turning Red and 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. Let’s look at why your tomatoes are not turning red and what to do to make them ripen.

Tomato fruits won’t turn red when the temperatures are above 85℉ (29.4℃) or below 50℉ (10 ℃). 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.  

Why are Tomatoes not Turning Red?

As a gardener, you are expecting all your tomatoes to ripen towards the end of the season. However, there are various things that can delay or prevent your tomatoes from ripening on the vines. The common causes include:

1. Extreme temperatures

Too high or too low temperatures can be detrimental to tomatoes in different ways. Temperatures above 85 degrees Fahrenheit [29.4 degree Celsius] are too hot for the tomatoes to ripen. According to the Cornell University Cooperative Extensions, the optimum temperature for ripening tomatoes is 70 to 75 degrees Fahrenheit [21.1 to 23.9 degree Celsius].

High temperatures that exceed 85 degrees Fahrenheit [29.4 degree Celsius] may slow down or stops the ripening process. The tomato plant produces carotene and lycopene pigments that give the fruits a red or orange appearance. The plant is unable to produce these pigments under high temperatures.

When the weather temperature is too high, you can harvest mature green tomatoes and place them in your kitchen cabinet to finish ripening. Providing shade over your plants can also help to slow down the temperature.

On the other hand, cold temperatures that are below 50 degrees Fahrenheit [10 degree Celsius] can also stop or slow the ripening process. It is common in areas that receive cold and wet springs or dry and cold summers. Cold temperatures can also ruin the flavor of tomatoes. The sugars in the fruits may turn into starch.

 When the temperatures are too low, you can harvest tomatoes that are not fully ripe and take them to the house to ripen fully. Tomatoes ripen on their own when placed together in a cabinet. They produce ethylene gas that promotes ripening. There is no need of wrapping them in paper bags or mixing them with other fruits like apples.

2. 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.

It is important to have more knowledge about the variety you are planting in your garden. When trying a new variety, make sure you know its maturity period and how ripe fruits look. 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 short growing seasons. They mature fast and hence giving the green fruits more time to increase in size and turn red before the temperature starts dropping below 50 degrees Fahrenheit. Some of the best short-season varieties include Early Girl, Glacier, and Stupice.

3. Excess foliage

Tomato plant requires 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 to red. To prevent this from happening, you are supposed to start pruning your tomato 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 on the ripening of fruits rather than producing more fruits. It also improves air circulation around the plant and hence decreases disease infections.

4. Overfeeding

Tomatoes may not ripen fast when the plant is overfed. Tomato plants require enough nutrients and water to grow healthy and produce high yields but you are supposed to slow down on fertilizer when the tomatoes are about to ripen.

5. Overwatering

Reducing watering to the point a plant is slightly stressed can trigger the ripening of the fruits. This trick can enhance quick tomato 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

There are various tips you can use to speed up the ripening process of tomatoes on the vine. It starts with planting the correct variety, providing optimal growing temperatures, and maintaining the plant properly.

1. Provide shade to your plants in hot temperatures

Temperatures that are above 85 degrees Fahrenheit [29.4 degree Celsius] inhibits 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

When a tomato plant is overfed and overwatered, it directs its energy toward the development of foliage at the expense of ripening the fruits. Tomato plant requires plenty of nutrients and adequate water during the growth period.

However, you are supposed to go slow on water and fertilizer after blossom. Slight water and nutrient stress encourage the plant to ripen the existing tomatoes.

3. Prune 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 as compared to what 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 fast. 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 toward the ripening of the fruits

6. Cutting off the suckers

Suckers are simply new plants that develop between each leave and the main stem. They suck more energy from the plant than 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. Removing some tomato 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 or small 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

How does pruning roots helps the green tomatoes turn red? Subjecting the plant to 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 when the temperature drops

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 in an area that is warm. The optimal temperature for ripening of tomatoes is 70 to 75 degrees Fahrenheit.

How long does it take for tomatoes to turn red?

Generally, after the flowers are pollinated, it takes 6 to 8 weeks for the tomatoes to enlarge and start ripening. However, there are various factors that determine the ripening of tomatoes. Some of the factors include optimal temperature, variety of the tomato planted, the growing area, and the natural ability of the plant to produce the hormone ethylene.

Tomato ripening is a complex process that involves various chemical reactions triggered by the plant. The plant produces carotene and lycopene pigments that give the fruit orange or red color. The plant increases acid levels that cause the starch in the fruits to be converted into sugars.

Tomatoes can also be ripened indoors due to various conditions like extreme temperatures, pests, sunscalds, and fall frost. However, you should pick them when their final color has started to appear and store them in a kitchen cabinet. The tomatoes should be able to ripen fully after a few days.

What month do tomatoes ripen?

Tomato fruits ripen from the month of June until the fall of the first frost. The warm and light conditions of summer are ideal for the ripening process. This process slows down as the 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 and remove any remaining flowers and small tomatoes from the plant. The plant will channel its energy toward the ripening of the remaining fruits.

Tomatoes that are not fully ripe can be picked and stored in a kitchen cabinet to ripen fully. Although 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 softens the fruit. You should only harvest the fruit and allow them to ripen indoors when all options to ripen them on the vine are exhausted.