Will Green Tomatoes Ripen Indoors? Which Ones, Where, How Long

Yes, some green tomatoes will ripen indoors, but only the ones that have reached the "mature green" stage. Colorado State University Extension says a shiny green fruit with a white to light green star on the blossom end will ripen off the vine, and a more matte green fruit will not. At about 70°F (21°C) expect roughly two weeks; near 55°F (13°C), about a month.

If you grew your plants in pots, this is the end-of-season job that follows the care in our container tomato guide. Four university Extension sources agree on the outline and differ on a few details, which are laid out below.

1. Step 1: Sort the fruit into three piles

Colorado State sorts tomatoes by how far along they are:

University of Alaska Fairbanks adds more ways to tell. A mature green fruit is almost full grown with cream-colored streaks at the blossom end. Its skin is tougher and does not rub loose when scraped with a thumbnail. Slice one open: if the pulp around the seeds has turned jellylike and the seeds slip aside instead of being cut by a sharp knife, it is mature enough. Fruit with soft, white seeds that a knife cuts through is too immature. Alaska says such fruit ripens much more slowly, usually shrivels, and ends up poorly colored and tough.

University of Minnesota Extension gives the same bottom-line test: if the bottom is as green as the rest, it is not worth ripening indoors, and tomatoes picked "truly green" will probably never ripen to a good flavor.

2. Step 2: Pick before frost, not after

Iowa State says to pick "just before the first frost," choosing fruit that is solid, firm and free of defects. Minnesota says to pick all the fruit and bring it indoors when frost threatens. Alaska adds that fruit from vigorous vines holds up better than fruit from nearly spent vines, which is more likely to decay, and says to pick before the vines are killed by frost.

Colorado State also suggests not waiting for the end at all: harvesting at the first blush gave that gardener better yields because fewer tomatoes were lost to sunscald, critters, or simply being missed until overripe.

3. Step 3: Prepare and store

1. Remove the stems, then wash and dry the fruit. Colorado State dries on a paper towel out of direct sun.
2. Wrap each tomato in newspaper (Iowa State), or leave them unwrapped. Alaska says mature greens can go either way.
3. Keep them one or two layers deep in a covered box or container (Colorado State). Minnesota prefers a single layer with no fruit touching.
4. Put the box somewhere dark (Colorado State, Iowa State, Alaska) and at a temperature from the table below; Minnesota just says room temperature. Light is not needed; Minnesota says warm temperatures matter more than light, and Alaska agrees light is not needed.
5. Check every few days. Colorado State removes ripe or nearly ripe fruit and Iowa State says to discard any damaged or decaying tomato.

4. How warm, and how long?

The sources do not recommend the same temperature, so here they are side by side, with Celsius converted for you:

The practical trade-off: a 15°F drop (70 down to 55) roughly doubles the wait, from about 14 days to about 30. If you pick on October 20, a box at 70°F should be ripening around November 3, while a box at 55°F would be closer to November 19. Colorado State warns that fruit ripened below 50°F will be bland, and Alaska says not to store tomatoes below 50°F or they will spoil.

5. Humidity and speed-ups

Colorado State notes that too much humidity causes mold and too little makes fruit shrivel. Alaska puts a number on the ideal: around 85 to 90 percent relative humidity prevents shriveling. The Colorado State author says too little humidity is the problem she runs into more often. Her trick for dry rooms is to set the tomatoes in a strainer over a little water in a covered container, without touching the water.

For faster results, Colorado State adds a banana or one or two red tomatoes to the green ones.

6. The hang-the-plant method

If there is a lot of fruit, Iowa State has an alternative: pull up the entire plant with the green fruit still attached, hang it upside down in a cool, dark spot, and pick tomatoes as they ripen. Alaska describes the same idea: pull the plants up by the roots before frost and hang them in a garage or crawl space that stays at 50°F or higher. The fruit will ripen over an extended period.

7. What to do with tomatoes that will not ripen

Colorado State uses them for green tomato recipes, and Alaska lists frying, sautéing, stewing in sauces, relish, and even bread or cake. Alaska notes that the sooner green tomatoes are used after picking, the better the finished product.

8. Key takeaways

• Only mature green (shiny skin, pale star on the blossom end) and blush-stage tomatoes ripen indoors; matte, immature fruit will not.
• Pick just before the first frost, one or two layers deep in a dark, covered box, and check every few days.
• About 70°F takes roughly 2 weeks and about 55°F roughly a month, and below 50°F the flavor suffers.
• Aim for high humidity without wetness: 85 to 90 percent prevents shriveling, but too much invites mold.
• Use the rest for cooking.