Few fruits are more fun to grow in the garden than tomatoes, but knowing when they're ripe and ready to eat can be tricky. "Tomatoes that are green are usually not yet ripe," explains Christopher Landercasper, director of farming operations for the Sonoma's Best Hospitality Group. "All tomatoes are green before they turn red, purple, or yellow, or some other color or combination." The problem is, if you leave tomatoes on the vine to ripen, you run the risk of animals or bugs enjoying them before you have the chance to.
Fortunately, it's possible to ripen green tomatoes after you've plucked them from the vine. "Many people choose to after-ripen tomatoes indoors," says Daniel Cunningham a horticulturist at Texas A&M AgriLife. "Not only does this practice prevent predation from wildlife and reduce exposure to extreme weather conditions, but it also might help give you more control and could even speed up the ripening process."
Bring all your green tomatoes indoors to ripen.
If you live in a region with cold weather extremes, Cunningham suggests harvesting all of the tomato fruits on the plants before the end of fall so they can after-ripen safely indoors in the winter. "Green tomatoes left on the vines during a freeze often succumb to the frost and become inedible," he explains. "Harvest them when the fruit begins to change color and soften to the feel. At this point most of the carbohydrates and sugars that will be sent to the fruit are already present in some form, but after-ripening indoors will enhance the flavor."
Don't harvest green tomatoes when they're too small.
When harvested too small, Landercasper says green tomatoes may rot before they have a chance to become ripe. "There is a fairly good way to tell which tomatoes have developed enough to further ripen," he explains. "Take an average sized tomato and cut it in half. If the gelatin holding the seeds is liquid enough that when you cut through the tomato, the seeds move, then tomatoes of that size and larger will ripen. However, if your knife cuts the seeds in half because the gelatin around the seeds is not liquid enough to allow the seeds to move away from the knife blade, then it will most likely rot before ripening."
Put green tomatoes in a paper sack.
Tomatoes and other ripening fruits, such as bananas, apples, and avocados, rely on ethylene gas—not sunlight—to ripen, which is why Cunningham says it's crucial to keep green tomatoes in a confined, temperature-controlled area once they're harvested so they can continue to mature. "Choose a confined spot, such as a paper sack or a cardboard box, that stays roughly around the 70 [degrees]-75 [degrees] range," he says. "This will allow for better airflow and less humidity, so a better concentration of natural ethylene gas can hang around."
Add a banana to the mix.
Since certain fruits release ethylene gas as they ripen, our experts say exposing a green tomato to another ripening fruit will help it mature faster. "If you need a tomato to ripen more quickly, put it in a paper bag with a ripe banana," Landercasper says. "The ripe banana will emit ethylene gas, and it will concentrate in the air in the bag, helping to speed the ripening of your tomato." However, if you don't have a banana on hand, Cunningham says an apple will also work.
Separate ripened tomatoes from unripened ones.
Depending on the type of tomato and when it was picked, Cunningham says some of your varieties might ripen in a few days, while others could take up to two weeks or more. "Check on your tomatoes frequently and remove those that have fully ripened," he advises. "Also, if at any time through the after-ripening process you notice a mushy fruit or tomato with a bad spot, quickly remove and discard."