Placing persimmons in a paper bag with a banana or storing them in a plastic bag with an apple are a couple ways to ripen them at home. Apples and bananas produce ethylene gas, a plant growth hormone that speeds the ripening process.
After placing the unripe persimmons in either type of bag with an ethylene-producing fruit, fold or tie the bag closed, and let the fruits ripen for one to two days. Other methods include freezing and thawing the persimmons or swabbing them with alcohol. Also consider letting them ripen by themselves at room temperature stored in a bowl, which takes about three to four days. Store ripened persimmons in the fridge away from other fruit for up to three days.
Before ripening persimmons, determine whether they are an astringent variety such as hachiya or a non-astringent variety such as fuyu. While hachiya persimmons are soft to the touch when ripe, fuyu persimmons may be hard or soft. A ripe persimmon is generally yellow-orange in color and 1 to 3 inches in diameter, and unripe hachiya persimmons are known for their bitter taste that turns into sweetness as they ripen. If you are unsure which variety you have, bite into one of the persimmons to check for bitterness.