Because tomatoes ripen from the inside out, you know you have a ripe tomato when the outside is a deep red color, is slightly soft when squeezed and the fruit seems to pop right off the vine when picked. However, tomatoes that remain green on the vine can become the bane of any self-respecting gardener. Knowing more about the ripening process and finding some quick fixes can save this year's crop from being a bust.
Mother Nature Might Be Working Against You
When tomatoes aren't ripening on the vine, it pays to do some research to find the reason. One factor might be the weather. When temperatures reach 86 degrees or hotter, the chemicals in tomatoes responsible for producing color, carotene and lycopene, are not produced. Another reason could be the plant itself. While an especially bountiful tomato plant might seem like a good thing, overcrowding is not. It takes a lot of energy to ripen many fruit at the same time, which can delay the ripening process for the entire crop.
You might be working against yourself
Several basis mistakes that gardeners can make also will slow or prevent tomatoes from ripening.
Before you begin planting, make sure the area receives plenty of sunshine; tomatoes, like many fruit, need at least seven hours of direct sunlight every day.
The plants also need to be planted at least a foot and a half apart.
If you use a fertilizer, tomatoes respond best to one with equal amounts of nitrogen, phosphorus and potassium; Nitrogen-heavy fertilizers will produce huge, beautiful plants, but not much fruit.
For plants exposed to hot weather, your best bet is to pick the tomatoes while they are pink and move them inside where whey can ripen in cooler temperatures (but not the refrigerator; tomatoes ripen best in temperatures between 65 and 70 degrees). Keep your plant healthy by watering it often, but not watering the leaves. Combat overcrowding by picking some of the mature unripened tomatoes and moving them inside, while leaving the others to mature successfully on the vine.
If you find yourself faced with an impending frost or you're simply lost for an explanation for your stubborn, unripened fruit, you might try putting a few green tomatoes inside a brown paper bag, along with a ripening banana or two. Ripening bananas produce the chemical ethylene, which can accelerate the ripening process of apples and tomatoes. For a larger crop of unripened tomatoes, the same effect can be achieved if you use a large cardboard box and more bananas. Just put something in the bottom of the box, like newspaper, to cushion the tomatoes.
If nothing else, remember: All is not lost. Green tomatoes can be delicious baked, fried, or used in a variety of salsas, relishes and pies.