06-07-2025
Why Aren't Your Tomatoes Turning Red?
Are your tomato vines covered in plump green fruits that just won't turn red? While tomatoes are relatively easy to grow, they can be finicky at times. Several factors slow down or stop the ripening process, causing tomatoes to linger in the green stage. Extreme temperatures are the most common culprit, but soil nutrition and plant care also play a role.
If your tomatoes are not turning red, don't fret. Find out the reasons behind this common problem and easy ways to promote your tomatoes to ripen, either in the garden or are not necessarily deep red when ripe. Heirloom tomatoes and hybrid tomato varieties offer plenty of variation in tomato colors. Before you jump to the conclusion that your tomatoes aren't ripening, check what color they are supposed to have when tomatoes is a slow process. The developing fruits require six to eight weeks to fully mature from the time of flower pollination. The time it takes the fruit to mature varies between tomato varieties, but sometimes there is more at play. Understanding how weather conditions, soil nutrition, and plant care impact fruit development will help you troubleshoot problems with ripening.
Temperature is among the most limiting factors when it comes to fruit set and ripening. Summer temperatures often exceed the optimal temperature range for ripening tomatoes, which falls between 68°F and 77˚F. In the fall, temperatures commonly drop below this range. When temperatures stray from the ideal range, the ripening process slows down.
Excessive heat, in particular, stops the ripening process because the pigments responsible for coloration, lycopene and carotene, are not produced when temperatures rise above 85°F to 90˚F. Heat-stressed plants will also divert energy away from ripening fruits and into survival, such as growing deeper roots.
When temperatures are too hot or too cold for vine ripening, tomatoes can be finished off the vine, as described below.
When plants fail to perform as expected, gardeners often reach for fertilizer or the watering hose, trying to nurse plants into production. However, this is detrimental to fruit ripening. Although tomato plants are heavy feeders, too much nitrogen fertilizer encourages leaf growth at the expense of flowers and fruits. The nitrogen needs of a tomato plant vary as the plant grows, requiring more during the early stages of establishment and vegetative growth. Excessive watering also slows down fruit ripening by reducing air movement in the soil.
When tomatoes fail to ripen, maintain regular irrigation practices to provide consistent moisture and time fertilizer applications according to plant development. Tomatoes benefit from a fertilizer low in nitrogen, high in phosphorus, and medium to high in potassium. Make your first fertilizer application when preparing the soil for planting using a complete fertilizer ( 5-10-5, 10-20-10, or similar). Fertilize again once the first tomato is golf-ball you would conduct a soil test in the spring or fall before planting, which will give you a baseline of the nutrient content in the soil and help you determine the fertilizer have been bred to produce ever-larger harvests, but sometimes tomato plants are simply overloaded with fruits. This is particularly true when plants are trying to manage other stresses, such as high heat or drought. The developing fruits compete with roots, flowers, and foliage for limited resources. The same stressors can also cause plants to lose foliage, which means there is less energy being produced through photosynthesis.
When fruits are failing to ripen during periods of stress, it may be helpful to thin out some of the fruit. Start with any fruits that are fully grown but stuck in the green stage and let these ripen on the countertop. This will reduce the energy demand on the plant, allowing more resources to reach the remaining tomatoes.
While tomato plants require full sun for the best performance, the fruits themselves do not require sun exposure to ripen. In fact, too much direct sun causes sunscald on developing fruits and increases temperatures in the plant canopy that delay pigment formation. Sunlight powers flower and fruit development through photosynthesis, which takes place in the leaves. It is the foliage, not the fruits, that needs direct sunlight. Therefore, pruning foliage is not conducive to ripening fruits. Keep the leaves in place to produce energy and shade the developing fruits.
It is natural for gardeners to want to 'fix' problems, but when it comes to ripening tomatoes, patience is your best course of action. Tomato fruits require adequate sugars and hormones to ripen. As gardeners, we can, however, hasten the process at times and adopt practices that direct energy toward developing fruits.
Pruning tomatoes benefits fruit development of indeterminate-type tomatoes by limiting excessive leaf growth that directs energy away from fruit production. It also reduces the number of fruit-producing branches, which prevents overloading plants with too much fruit.
When plants overproduce, thinning fruits, as described above, limits competition for water and nutrients. Pruning also increases airflow through the plant foliage, which helps fight foliar diseases and keeps plants healthier.
A developing tomato plant produces a main shoot, called a vine, from which suckers (side shoots) and fruit clusters develop in the leaf axils, which is where the leaves meet the stem. Begin pruning when the plant produces its first flower cluster. Follow these steps:
Remove all suckers except the first one below the lowest flower cluster. This is the strongest sucker and can be left as a secondary shoot for fruit production.
Remove suckers by pinching them between your thumbnail and forefinger, cutting them as close to the stem as possible. Use pruners on thicker suckers.
Remove the bottommost leaves to limit fungal infections and reduce competition for water and nutrients.
It is best to remove suckers when they are still small. Check the main vine and secondary shoot regularly for new suckers and remove them promptly. As fruits in the upper canopy begin to plump, stop pinching suckers from the upper portion of the vine to allow the canopy to develop. This will shade fruits and protect them from sunscald.
When weather conditions do not favor ripening fruit on the vine, fully grown green tomatoes can be harvested and ripened indoors. Many gardeners do this in the fall before a frost. Tomatoes must reach their mature size before harvesting, as immature green tomatoes will never ripen. Look for the first hints of color change to indicate a tomato is ready to harvest. Even tomatoes that refuse to turn red will lighten in color to a paler green, or even take on yellowish hues.
Store harvested tomatoes indoors at room temperature. Do not refrigerate tomatoes (even fully ripe ones) as the flavor deteriorates, and green tomatoes need warmer temperatures to ripen. Remember, the optimal temperature for ripening is between 68°F and 77˚F; this applies indoors, too. Green tomatoes may take several days to fully ripen.
Tomato ripening is powered by ethylene, a hormone produced by plants. Many of the tomatoes sold at grocery stores were harvested while still green and ripened through exposure to ethylene gas. Plants and fruits also produce ethylene naturally. We can use this to our advantage when ripening tomato fruits off the vine by placing a few green tomatoes together in a paper bag. This creates a closed environment for the ethylene being released by the tomatoes to collect and power ripening.
Some fruits release a lot of ethylene as they ripen. Bananas, for example, are ethylene powerhouses, which is why many people store them away from other fruits. Use the ethylene released by bananas (or apples or avocados) to hasten tomato ripening by placing them together on the counter or in a fruit bowl.
Green tomatoes ripened indoors taste almost as good as their vine-ripened counterparts, but not quite. For the best-tasting tomatoes, allow the fruits to fully ripen on the vine. Follow proper pruning, watering, and fertilizer to maintain healthy, vigorous plants and reduce competition for limited resources. Be patient. Tomatoes take a long time to ripen, but the flavor is worth the wait.
Read the original article on Southern Living
