The desire for a perfect, garden-fresh tomato often runs into the problem of stubborn green fruit, especially when the growing season nears its end or uncooperative weather arrives. While tomatoes can be slow to transition from green to vibrantly colored, horticultural adjustments and post-harvest techniques can significantly accelerate this natural process. Understanding the science behind ripening allows for targeted strategies to achieve a sweet, juicy harvest.
Understanding the Ripening Mechanism
Tomato ripening is a climacteric process, characterized by a distinct surge in respiration and the production of the plant hormone ethylene. This gaseous compound acts as the internal signal that triggers the fruit’s final maturation stage. Once the internal concentration of ethylene reaches a certain threshold, typically between 0.1 and 1.0 parts per million (ppm), the ripening cascade begins. This cascade involves the activation of enzymes that soften the fruit’s flesh, increase sugar content, and break down chlorophyll, allowing the red carotenoid pigments to develop.
Techniques for Accelerating Ripening On the Vine
To encourage faster ripening while tomatoes remain attached to the plant, management techniques focus on redirecting the plant’s energy toward the existing fruit.
One effective method involves pruning the plant by removing non-fruiting side shoots, known as suckers, that sprout between the main stem and a leaf branch. This action directs the plant’s resources and stored sugars away from producing new foliage and toward maturing the current fruit load.
Another helpful technique is “topping” the plant, which means cutting off the main growing tip, especially about six weeks before the expected first frost. Removing the terminal bud prevents the plant from producing any new flowers or fruit that would compete for energy.
Adjusting water availability can also prompt a final push toward maturity. Slightly reducing the amount of water during the final weeks of the season induces a mild stress response. This stress signals the plant to hasten the maturation of its seeds, which are encased in the fruit. This method must be applied carefully to avoid severe wilting or the development of blossom end rot.
Post-Harvest Methods for Quick Ripening
When cold weather threatens or the goal is to ripen mature green fruit indoors, the most effective method involves trapping the naturally produced ethylene gas. This is done by placing the firm, mature green tomatoes inside a loosely sealed container, such as a paper bag, a cardboard box, or a single-layer tray covered with a cloth.
For an even faster result, introduce a companion fruit that is a prolific producer of ethylene, such as a ripe apple or a banana. Placing one of these fruits into the container significantly boosts the gas concentration, shortening the ripening time. The optimal environment for post-harvest ripening is a consistent temperature range between 65°F and 70°F (18°C to 21°C).
Temperatures above 85°F (29°C) inhibit the production of red pigments, resulting in fruit that is soft but yellowish-orange. Conversely, storing green tomatoes below 50°F (10°C) can cause chilling injury, leading to poor color development, mealy texture, and flavor loss. Therefore, a dark location within the ideal temperature range, away from direct sunlight, provides the best conditions for successfully ripening off-the-vine fruit.