Place hard supermarket tomatoes in a paper bag to soften and ripen them. Speed up the process by adding to the bag a ripening apple or pear, which will release ethylene gas. (Commercial producers use this naturally produced gas to speed the ripening of fruits that are picked green.) Open the bag periodically to check the ripening process. Ideally, you want a firm, brightly colored tomato.

Wrap tomatoes in newspaper. This method works well for green tomatoes from a late-season harvest. Select mature green tomatoes that are firm to the touch and free of holes, scars or cracks. Gently wrap each fruit separately in a sheet of newspaper and place in shallow boxes or upon shelves. Keep them in the basement or other cool, dark place. Check the tomatoes frequently for any specimens that begin to rot and remove them before they spoil other fruits. Once you see color emerge on the fruit, remove the paper and bring them into room temperature to finish ripening.

Pull up the entire plant to save late-season tomatoes just before a frost. If you have a garden full of green tomatoes you can save them by hanging the plant upside down in your basement or other cool location. The tomatoes will continue to mature naturally. Pick the tomatoes as they ripen.