It is easy to tell when a tomato is ripe because it looks dark red and healthy, its skin feels firm but the tomato is slightly soft in your grip, and it is easily plucked from the vine. Sometimes, however, a gardener will be faced with tomatoes that just do not seem to be turning red. Here are a few possible reasons and solutions:
Make sure you have planted the tomato plants correctly. They should have enough growing space between each other. If you use fertilizer, do not use the ones with too much nitrogen. These fertilizers will make the plants grow large, but they will not bear many tomatoes.
Tomatoes ripen in warm temperatures, but they will not ripen in temperatures above 86 degrees Fahrenheit (30 degrees Celsius). If you live in an area with pretty hot summers, it is best to pluck the tomato from the vine when it is still pink and let it ripen indoors where it is a little cooler (60 to 75 degrees Fahrenheit, 16 to 24 degrees Celsius).
Watch out for frost warnings. If frost is predicted and your tomatoes are still green, it is a good idea to protect your tomatoes with bed sheets, plastic, or enclose them in a big box for the night. Frost can prevent your tomatoes from ripening any further. If your green tomatoes are almost full-sized, you can try to pick them and eventually they will ripen a little bit. If you would like, you can eat the smaller ones fried.
If you place your tomatoes near ripening apples or bananas, the ethylene produced can help the ripening process. You can place your tomatoes in a newspaper-lined open cardboard box with a few ripening bananas and store them in a cool but somewhat humid area. Your tomatoes should ripen within a week or two.
If you fix your methods or try some of these new ones, you will soon have fresh, ripe, red tomatoes for your salads and salsas!