Bring green tomatoes indoors before frost, then sort the harvest.

1. Harvest before a damaging frost

Watch your local forecast instead of a universal autumn date. Before frost threatens the crop, collect sound fruit that has reached mature size. Remove stems carefully so they do not puncture neighboring tomatoes.

Set aside cracked, bruised or damaged fruit rather than mixing it into a box intended for slow ripening. Discard decay. Bringing frost-injured fruit indoors does not undo the damage. This is a fresh-fruit ripening plan, not a canning or preservation method.

2. Decide which fruit is worth waiting for

Color varies with cultivar. Some ripe varieties remain green, yellow or orange, so compare with the label and previous fruit rather than insisting every tomato must become red.

3. Use a shallow box, not a hot windowsill

Clean and dry the selected fruit. Arrange it in one layer on clean paper in a box or tray so you can inspect each tomato. Iowa State also describes wrapping mature green fruit individually in newspaper for slower ripening.

Keep the fruit out of direct sun. Light is not needed for this process, and a sunny window can make conditions harder to control. Choose a spot where the fruit will not be crushed, forgotten or exposed to freezing temperatures.

4. Let temperature control the pace

A cool room around 60–65°F (16–18°C) supports a slower ripening plan. Bring fruit that begins coloring to ordinary room temperature if you want it to finish sooner. Colorado State describes faster ripening near 70°F (21°C) and slower progress closer to 55°F (13°C).

A refrigerator is not a good place to ripen green tomatoes. Do not promise a fixed number of days: cultivar, harvest maturity and the actual room temperature all affect the result. Sort batches by stage to make progress easier to follow.

5. Check often and use ripe fruit

Inspect every few days, including the underside of each tomato. Remove fruit with mold, leakage or soft decay promptly; keep ripe fruit separate from the waiting batch. Persistent condensation or shriveling is a reason to reassess the storage conditions.

A ripe banana or tomato can speed ripening through ethylene, but it cannot turn immature fruit into a mature harvest. If you try it, keep checking the box. For plants still outdoors, use the first-frost checklist; for next season, see the cherry tomato guide.