A standard-sized tomato takes 20-30 days from blossom set to reach full size, usually called "mature green". After that, it takes 20-30 days to ripen. Depending on the cultivar, tomatoes can be picked when they turn red, pink, yellow, or orange.
Temperatures between 68°F and 77°F (20-25°C) are optimal for tomato ripening; tomatoes ripen slower when temperatures are cooler or warmer than this range. A tomato will not ripen if the temperature is less than 55°F (13°C) and more than 85°F (29°C). It is possible to bring a mature green tomato to full ripeness and color off the vine at room temperature, between 70°F and 75°F. Whether tomatoes are picked on the vine or off the vine, once they have moved past the "mature green" stage, they will be as flavorful and as ripe as if they had been picked off the vine.
The harvest time of your tomato crop can be estimated using the estimated days to maturity, fruit size, and color. The maturity of tomato plants cannot be accelerated faster than nature allows. It is possible, however, to expedite the tomato harvest when the temperature is right.
How to know a tomato is ripe
The inside of the tomato ripens first. When a tomato is ripe, its skin will turn red (if the variety is red), and the fruit will be ready to pick. For varieties that are supposed to be green at harvest, you must keep track of the days from transplanting to know when to harvest.
Tomato ripening and temperature
When temperatures exceed 86°F, a red tomato will usually not turn red. The fruit may look yellowish-orange instead of red if you live where it is very hot during the summer. If the temperature exceeds 85°F, the red pigment will not form.
Ways to speed tomato ripening on the vine
The following steps can help you speed up the overall ripening of tomatoes on the vine once they reach the mature green stage:
Pick fruit as soon as it starts to show color; this will allow other fruit on the vine to gain size and come to harvest more quickly. Room temperature is good for ripening tomato fruit when picked at the first sign of color. Fruit ripening off the vine is just as tasty as fruit matured on the vine. Cut or gently twist off fruits supporting the vine at the same time. You should not leave overripe fruits on the vine because they can decrease productivity and spread disease.
Remove flower clusters
Pluck new flower clusters from tomatoes that have already set fruit. With the flowers removed, the plant's energy will be directed toward ripening the fruit already on the vine. To ensure the fruit on the plant makes it to harvest without frost or cold damage, remove flower clusters no later than a month before the first expected frost.
Remove small or excess fruit.
Remove small or excess tomatoes from the plant. If you remove immature fruit or fruit you won't use, the plant will devote its energy to ripening larger, already mature fruit. It is possible to ripen tomatoes at room temperature once they reach "mature green" size.
Remove some leaves
Suckers and lower leaves should be pinched off. The main stem and lateral branches of tomato plants produce new shoots almost continuously, called suckers. This new growth should be pruned or pinched away so that the plant can devote its energy to producing and ripening fruit rather than new leaves. To prevent sunburn, leave leaves above fruit or fruit clusters in place. The leaves low on the plant should be removed if they turn yellow or brown or if they are diseased.
Reduce water and food late in the season.
In order to encourage "mature green" fruits to ripen, reduce water and fertilizer use. Excess nitrogen in fertilizers promotes new leaf growth at the expense of fruit growth and maturity. The plant's energy will be directed away from ripening new fruit and toward ripening fruit already on the vine as the fruits grow mature. (Use fertilizer low in nitrogen 4-8-4 for tomatoes.) Reducing water as fruit matures will enhance ripening (and concentrate flavor.)
Stress roots near season end
Plant roots can be twisted gently at the crown to shift or rotate roots, causing the plant to stop growing, ripen, and go to seed as a result of nutrient and moisture distribution from roots to fruit.
Protect plants from extreme temperatures.
To protect plants from temperatures below 60 degrees Fahrenheit (16 degrees Celsius), wrap cages in clear plastic or cover them with frost blankets; and drape shade cloth over frames to protect tomatoes from the harsh sun and temperatures above 90 degrees Fahrenheit (32 degrees Celsius). The ripening and maturation of fruit can be slowed and even halted by extreme temperatures. When fruits have turned color, pick them and ripen them indoors between 70°F and 75°F (21-24°C).
Mulch with plastic sheeting
Plastic sheeting or aluminum foil in silver- or red-colored hues can help speed growth in low-temperature or overcast conditions. Plants ripen more quickly by a week or more when light reflected from colored plastic or foil stimulates the movement of carbohydrates into developing fruit.
How to ripen tomatoes in short-season regions
Here are some tips to speed up tomato harvests in regions where tomatoes are consistently slow to ripen:
Grow early to mature varieties
Choose tomato varieties with shorter optimum temperature periods. A variety of tomatoes that can be harvested within 55 to 70 days after transplanting may be the best option for regions where the temperature does not stay within the optimum range for the fruit to ripen.
The plants should be started indoors and hardened off four to five weeks ahead of the last frost. Three weeks before the last frost date, plant seedlings in the garden. Plant the tomato plant about an inch deeper than in their cartons and then watered in. Cover these transplants with cloches or tomato cages wrapped in plastic until nighttime temperatures are consistently above 55°F (13°C).
Keep plants warm
Plants with low temperatures can be heated at night by placing self-standing sleeves or water around them or by flanking them with flat tiles that absorb the day's heat and radiate it at night. Tomatoes should be planted near a west or south-facing wall or side of a building. During the day, the wall will absorb the sun's heat and radiate it back out at night.
Stake or cage plants
A stake or cage can be used to support tomato vines. Plants should be grown up so that the fruit can be exposed to the sun and air. We build tomato cages from cattle panels.
To aid pollination, shake flower clusters on warm, calm days. Hot, windy days or cool, wet weather can inhibit pollination. Flowers drop when not pollinated; fruit will not develop where pollination does not occur.
Ways to ripen tomatoes off the vine
It is possible to ripen tomatoes off the vine, but the flavor will not be as intense as if the tomatoes were left on the vine to ripen:
- When tomatoes are off the vine, they do not require light to ripen. The tomatoes will ripen unevenly if they are placed in a sunny window to ripen. Keep picked tomatoes away from windows where temperature ranges between 65 and 70 degrees Fahrenheit.
- A paper bag containing an apple or banana can be used to redden tomatoes off the vine. The ripening process is sped up by ethylene gas given off by the fruit.
- Unripe tomatoes can ripen in a cool, dark place, but their flavor will be less intense than vine-ripened tomatoes.
- Refrigerating partially ripened tomatoes is not recommended. Very cool temperatures will slow down the ripening process. Picked tomatoes should ripen at room temperature in a dark place.
- It is best to store fully ripened tomatoes at room temperature, but they won't last very long.
- Canning or freezing tomatoes at their peak of ripeness preserves their flavor and nutrients better than any other vegetable.
- You should pluck all new flowers off of your tomato plants about a month before the first frost. Instead of producing new tomatoes that won't have time to mature, the plant will direct its energy to ripen the tomatoes already on the vine.
- You can wrap each green tomato individually in newspaper and then place them loosely in a single layer in a cardboard box to prevent them from squashing each other at the end of the season. Until they ripen, keep them cool and dry.
- You can hang the entire truss of cherry tomatoes in the kitchen or garage until the fruit ripens and is ready for harvest if you still have unripe tomatoes on the vine when the frost hits.