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If the weather has gotten cold but you still have green tomatoes, then you’ll have to finish the ripening process indoors. Pick each tomato and be careful not to bruise or crush any. Inspect them and dispose of any damaged ones. They won't ripen properly. Leave the stem attached on all the tomatoes you pick. This helps them ripen better. after picking them. Before you start the ripening process, wash each tomato thoroughly. This removes any bugs or mold spores that could damage the tomato during the ripening process. Run each tomato under cool, running water. Then dry it with a towel. Make sure the tomatoes are dry because mold grows best in moist environments. The specific container depends on how many tomatoes you have. If you only have a few, then use a paper bag. If you have a full vine or more, use a cardboard box with more room. Arrange the tomatoes so they don’t touch each other. If you have a lot of tomatoes to ripen, use multiple boxes or bags. Too many tomatoes in one place will eat up all the ethylene, the chemical that makes plants ripen. Bananas naturally produce ethylene, the chemical that makes plants ripen. While tomatoes produce the chemical on their own, bananas produce much more, and boost the ripening process. Introduce a banana to aid the tomatoes.  Use a banana that is still slightly underripe and still has green ends. A brown banana won’t produce anymore ethylene. If you place the tomatoes in multiple containers, add a banana to each one. Tomatoes need an ethylene-rich environment to ripen properly, so seal the container you’re using. This traps the ethylene and helps your tomatoes absorb as much as they can. If you’re using a paper bag, roll the top down. If you’re using a box, close the top and use a strip of tape to hold it closed. Don’t make the container airtight or too tight to open. You’ll still have to check every day for signs of rotting, bruising, or mold growth, so make sure you can open the container easily. Open the container each day and check each tomato. Look for dark brown or black spots on its skin, which indicate that the tomato is starting to rot. Also look for growths on the tomato from mold. Remove tomatoes with these signs and dispose of them. When the tomatoes turn red, they’re ripe and ready to use. Pick out the ripe ones and enjoy!  In warmer environments, around 65–70 °F (18–21 °C), the ripening process takes 1-2 weeks. In cooler environments, the process takes closer to a month. Use the ripe tomatoes within a week of removing them for optimal taste and freshness. If you won’t use them right away, place them on a windowsill in direct sunlight.

Summary:
Pick the tomatoes if they aren’t ripe yet when the season ends. Wash and dry the tomatoes Place the tomatoes in a paper bag or cardboard box. Add a banana with green ends to the bag or box. Seal the bag or box. Check the tomatoes daily for mold or rotting. Remove the tomatoes when they ripen.