When the growing season ends or garden pests become too numerous, bringing unripened tomatoes indoors allows for the continuation of the natural maturation process. Tomatoes are classified as climacteric fruit, meaning they continue to ripen after being harvested, unlike non-climacteric fruit such as grapes or strawberries. The trigger for this change is the plant hormone ethylene, a colorless, odorless gas that the fruit itself produces. By harvesting tomatoes before a frost or pest damage occurs, you can create a controlled environment to harness this natural gas and achieve a flavorful final product.
Assessing Tomato Maturity for Indoor Ripening
Not every green tomato will successfully ripen indoors; a certain level of physiological maturity must be reached while still on the vine. The ideal candidates are those that have progressed to the “mature green” stage, meaning they have reached their full size and their surface skin has developed a slight sheen. At this stage, the fruit is firm to the touch, and the internal pulp, called the locular gel, has developed a jelly-like consistency.
The best time to pick a tomato for indoor ripening is at the “breaker stage,” which is when the first hint of color appears, typically as a blush near the blossom end. This slight color change indicates that the tomato has begun its natural production of ethylene gas. Tomatoes picked at this initial color break will generally develop a flavor profile much closer to a vine-ripened fruit. If a tomato is still a dull, matte green and small for its variety, it is likely too immature and may shrivel or rot before it can ripen.
Establishing the Optimal Ripening Conditions
Successful indoor ripening relies on controlling temperature, light, and air flow to encourage the necessary biochemical reactions. The optimal temperature range to facilitate the ripening process is between 65 and 70 degrees Fahrenheit (18–21 degrees Celsius). Temperatures much higher than 85°F (29°C) can cause the ripening process to stall and prevent the development of the red-pigment compound lycopene.
Light is not necessary for the ripening process, and direct sunlight can cause the tomatoes to cook or develop soft spots. Instead, the fruit should be stored in a dark or dimly lit location, such as a basement, closet, or pantry. Adequate air circulation is also important to prevent the buildup of moisture, which can encourage the growth of mold or rot on the fruit’s surface. A slightly humid environment, however, will prevent the tomatoes from shriveling as they mature.
Practical Methods for Speeding Up Ripening
The core principle behind all fast-ripening techniques is to confine the naturally produced ethylene gas around the tomatoes. A simple and effective method involves placing the fruit in a loosely closed paper bag or a cardboard box. The container traps the gas, increasing its concentration and accelerating the color change and softening.
You can further accelerate this process by introducing an ethylene donor fruit, such as a ripe banana or apple, into the container with the tomatoes. These fruits are prolific ethylene producers and will significantly boost the gas concentration, often cutting the ripening time in half. For this method, a single apple or banana is usually sufficient for a small batch of tomatoes and should be checked daily.
For larger harvests, wrapping each tomato individually in a sheet of newspaper is a traditional and highly effective technique. The newspaper serves two purposes: it isolates each fruit to concentrate its own ethylene, and it prevents contact between tomatoes, which stops potential rot from spreading. When using any of these methods, a timeline of four to 14 days is typical, but you should check the containers every two to three days to remove any fruit that has ripened or shows signs of spoilage.