ripen green tomatoes
1 In a paper bag. 2  Place green tomatoes in a paper bag with a piece of ripe fruit, such as an apple or banana. 3  Ripening fruit gives off ethylene gas. 4  Ethylene gas works two ways â it also stimulates ripening. 5  Thatâs why in an enclosed environment, like a paper bag, the apple or banana will help green tomatoes turn red.ays to ripen green tomatoes off the vine. Light isnât necessary for ripening green tomatoes! Try these easy methods. 1  In a paper bag. 2  Place green tomatoes in a paper bag with a piece of ripe fruit, such as an apple or banana. 3  Ripening fruit gives off ethylene gas.