When ripening citrus fruits and tomatoes, many people reach for a brown paper bag, which traps the ethylene gases produced by these fruits. Because the fruit absorbs the gas, it ripens faster. Strawberries only produce a small amount of the gas, which means this isn't an effective ripening method. The best way to get your strawberries to ripen is to leave them sit in the open air at room temperature. It can take anywhere from a few hours to several days, depending on what stage they begin at.