Tomato ripening depends on temperature, light, and plant maturity — not just time on the vine
Tomatoes turn red when the plant reaches a certain age and the fruit receives the right combination of warmth, light, and nutrients. If your tomatoes are staying green, one of these conditions is missing. The most common culprit is temperature: tomatoes stop ripening below 68°F and slow dramatically above 85°F. The second most common reason is that the fruit straightforward hasn't had enough time — many varieties need 20 to 30 days from the moment they stop growing larger before they begin to change color.
The good news is that ripening problems are almost always fixable once you know which condition is holding your plants back. A green tomato on a healthy vine is not a failed tomato; it is a tomato waiting for the right signal.
Key Takeaways
- Tomatoes need soil and air temperatures between 68°F and 77°F to produce the pigments that make them red; below 68°F they stop ripening entirely.
- Fruit that stops growing larger needs 20 to 30 additional days of warm weather before it begins to change color, depending on variety.
- Too much nitrogen fertilizer pushes the plant to make leaves instead of ripening fruit, and can delay color change by weeks.
- Removing some leaves in late summer lets more light reach the fruit and speeds ripening, but removing too many stresses the plant and slows it further.
- Tomatoes picked green will ripen indoors at room temperature over one to two weeks, so a late-season harvest does not mean a wasted crop.
Temperature is the main reason tomatoes stay green
Tomatoes produce lycopene and carotene — the pigments that make them red and orange — only when nighttime temperatures stay above 68°F. During the day, the plant can be warmer, but the night temperature is what matters most. If your nights are consistently below 68°F, your tomatoes will not ripen, no matter how long they sit on the vine.
This is why tomatoes grown in cool climates often stay green until late summer, or fail to ripen at all before frost arrives. If you live in a region where September nights drop below 68°F, you may need to pick your tomatoes green and ripen them indoors, or choose faster varieties that mature in 60 to 70 days instead of 80 to 90.
Heat above 85°F also slows ripening. When it is very hot, the plant focuses on keeping itself alive rather than coloring fruit. If you are in a hot climate and your tomatoes are stalling, afternoon shade cloth or consistent watering can help the plant manage heat stress and resume ripening once temperatures drop.
Fruit needs time to mature before it can change color
A tomato does not start ripening the moment it appears on the vine. It first has to reach full size — the point where it stops growing larger. Only after that does the plant begin to produce the pigments that turn it red. This lag time is usually 20 to 30 days, depending on the variety.
If you planted your tomatoes late in the season, or if your variety is a long-season type (like 'Brandywine' or 'Cherokee Purple'), the fruit may still be in the growth phase when you expect it to be red. Check whether the tomato is still firm and hard, or whether it has begun to soften slightly. A softening tomato is beginning to ripen; a hard, full-sized one is waiting for the right temperature to start.
Early-season varieties like 'Early Girl' and 'Stupice' mature in 50 to 65 days and are better choices if you have a short growing season or cool nights. Mid-season varieties take 70 to 80 days, and long-season types need 85 to 100 days or more.
Too much nitrogen fertilizer delays ripening
Nitrogen pushes plants to make leaves and stems. If you have been fertilizing heavily — especially with a high-nitrogen formula — your tomato plant may be so busy growing foliage that it is not putting energy into ripening fruit. This is one of the most common mistakes in home gardening.
Once fruit has set, switch to a fertilizer lower in nitrogen and higher in phosphorus and potassium. A formula labeled something like 5-10-10 or 2-8-8 will support ripening instead of leaf growth. If you have been using a balanced fertilizer like 10-10-10, stop or cut back to half strength. Many gardeners find that stopping fertilizer altogether once fruit is visible produces better color and flavor.
If your soil is naturally rich or you added compost before planting, you may not need to fertilize at all. A soil test can tell you whether nitrogen is actually low or whether you are adding more than the plant needs.
Leaf removal can help, but too much makes ripening worse
Removing some leaves in late summer allows more light to reach the fruit and can speed ripening by a week or two. The key word is some. Leaves are what the plant uses to make energy, and removing too many stresses the plant and actually slows ripening.
A safe approach is to remove only the leaves that are directly shading the fruit — the ones between the fruit and the sun. Leave all the leaves above the fruit and most of the leaves below it. Remove no more than one or two leaves per plant per week, and stop removing leaves once the first tomato begins to show color.
Never strip the plant bare or remove all the lower leaves at once. A plant that loses too many leaves at once will focus on recovering rather than ripening, and you may end up with sunscald (white or yellow patches on the fruit) from sudden exposure to intense sun.
Diseases and pests can slow or stop ripening
Fungal diseases like early blight and septoria leaf spot weaken the plant by killing leaves, which reduces the energy available for ripening. If your plant has brown spots on the leaves or is losing leaves from the bottom up, disease may be the reason your tomatoes are not turning red.
Remove affected leaves as soon as you see them, and improve air circulation by spacing plants farther apart or pruning lower branches. Water at the soil level rather than overhead to keep leaves dry. If the disease is severe, the plant may not have enough leaf area left to ripen fruit before frost, and you should pick the tomatoes green.
Pests like spider mites and whiteflies also stress the plant by feeding on leaves. If you see webbing, yellowing leaves, or tiny insects on the undersides of leaves, spray with insecticidal soap or neem oil according to the label, and repeat every 7 to 10 days until the pest is gone.
Picking green tomatoes and ripening them indoors works well
If frost is coming and your tomatoes are still green, pick them. A tomato picked at the mature green stage — when it has stopped growing and the skin has begun to lose its deep green color — will ripen indoors in one to two weeks at room temperature (around 70°F).
Place the tomatoes in a cardboard box or paper bag in a dark or dimly lit spot. Do not refrigerate them; cold stops ripening. Check them every few days. As soon as they begin to show color, move them to a sunny windowsill to finish ripening and develop full flavor.
Tomatoes ripened indoors will not taste quite as good as those ripened on the vine in warm sun, but they will be far better than tomatoes left to rot on a frost-killed plant. This method is standard practice in cool climates and is not a sign of failure.
Frequently Asked Questions
Can I speed up ripening by picking the tomato early?
No. A tomato picked before it reaches full size will not ripen properly indoors. Wait until the tomato has stopped growing larger and the skin has begun to lighten before you pick it. At that point, ripening indoors works well.
Will wrapping green tomatoes in newspaper make them ripen faster?
No, and it may actually slow ripening by blocking light. Newspaper or paper bags are useful for storing tomatoes while they ripen, but they do not speed the process. Warmth and light are what matter — keep them at room temperature in a spot with indirect light.
Is it bad if my tomato plant has flowers but no fruit yet?
Not necessarily. Flowers drop and fail to set fruit when nighttime temperatures drop below 55°F or above 90°F, or when the plant is stressed by drought or disease. Once temperatures stabilize in the right range and the plant recovers, new flowers will set fruit. This is normal and does not mean the plant is dying.
Should I stop watering to make tomatoes ripen faster?
No. Drought stress slows ripening and can cause problems like blossom-end rot and cracking. Water deeply and regularly — about one inch per week, or more in very hot weather. Consistent moisture supports both ripening and fruit quality.
What if my tomatoes are turning orange instead of red?
Orange tomatoes are usually ripe and ready to eat, depending on the variety. Some varieties like 'Sungold' and 'Apricot' are naturally orange when fully ripe. If your red variety is staying orange, it may be a temperature issue — very hot weather can prevent full red color development. Taste one to see if it is ripe; if it is soft and sweet, it is ready.