How Long Does It Take for a Tomato to Turn Red After Being Full Grown on a Plant?

Temperature

• Lycopene is the chemical that turns the fruit red. When temperatures are higher than the mid 90s, lycopene and carotene are not produced except during the night when temperatures drop below 85 degrees. Toward the end of the growing season, the cooler temperatures help ripen the last of the fruit more quickly. Once temperatures drop below 50 degrees, even fully developed green fruit will be damaged and unable to ripen, though partially red ones may still ripen indoors. Harvest any fully developed green fruit before nighttime temperatures fall below 50 degrees.

Time Frame

• Big Beef Tomatoes, as an example, produce their first fully mature fruits 34 days after the seedlings are transplanted. The first fruits begin to color 18 days after they mature and don't ripen for nearly 30 days. It can take full-size green fruits of any tomato weeks to mature. Full-size green tomatoes will even ripen off the vine, either still attached to the stem or wrapped in newspaper or kept inside paper bags or cardboard boxes. Paper containers help the process along by collecting gases released during ripening, speeding ripening by days.

Mature Green Tomatoes

• To determine when a tomato is fully mature and able to ripen off the vine, pick a tomato to test. Cut one in half with a sharp knife. The interior should be jelly-like or sticky and yellowish inside or have a reddish tinge at the blossom end according to Ross Penhallegon, Oregon State University Extension horticulturist. Tomatoes that have soft seeds that are easy to cut through and pulp that is not yet jelly-like will not ripen off the vine if picked. If clipping fruit to mature off the vine, include a short stem piece. Longer pieces may punch holes in other tomatoes packed with it, so keep them short. Don't rip out the stems because it may leave a hole that allows decay to form inside and rot the fruit.

Ripening Green Tomatoes

• If ripening green tomatoes off the vine, store them at temperatures between 55 and 70 degrees F. After they are ripe, store them at 45 to 50 degrees with a 90 to 95 percent humidity. Green tomatoes will not ripen in a normal refrigerator. The cold temperatures destroy the ripening enzymes and the fruit will spoil without ripening further. Place green tomatoes in well-ventilated cardboard boxes, paper bags or newspaper wrappings at room temperature. Check them every two to three days, remove and destroy any that appear to have spoiled or which have damaged or discolored places on them. These will spread rot to the rest of your tomatoes if left behind. Ripened this way, tomatoes will be ready in 14 to 28 days, slower at 55 degrees and faster at 70. Keep them in the dark. They ripen best without sunshine once removed from the vine.