Why Aren’t My Tomatoes Turning Red?

'Green Zebra'

This has been a WEIRD and disappointing gardening season.  Here in Zone 9 we had winter, then 3 weeks of spring, followed by the most pathetic summer ever.  The Central Valley of California is known for blazing hot, 100° F August days followed by muggy, miserable evenings.  In fact, local businesses use the theme “Hot August Nights” to advertise car shows and concerts.

This year, daytime temps haven’t passed 95 F and at night the temperature has even dipped into the high 50′s!  And yes, although it may sound strange, I actually do miss 100 degree weather and muggy nights. ;) And I’m not the only one. Tomato plants  NEED warm temperatures both at night and during the day.

'Black Cherry'

In the garden, I’ve harvested handfuls of ‘Sweet 100′s and ‘Black Cherry’ for the past three weeks. For the larger varieties, ‘Early Girl’ and ‘Cherokee Purple’ have yielded a miserly 10 tomatoes. By now I should be knee deep in tomatoes and absolutely sick of them. After all, I put in 9 plants! I even planned a salsa party.

So why aren’t tomatoes turning red? It has to do with the combination of Maturity+ Mother Nature + Variety.  In a “normal” year, the equation equals perfectly ripe, yummy tomatoes.  But in this far from normal year, many gardeners are frustrated.

Seeing tomatoes hang green on the vine week after week, day after day is unprecedented. Many gardeners are in shock, while others chose to deny the facts. A few have cursed and pulled out plants, prepping their soil for broccoli and Brussels sprouts. And there may even be some (but no, I hate to write this!) eyeing their neighbor’s reddish, almost ripe ‘maters with a gleam in their eye and “Oh no, PLEASE don’t do it!!” Don’t stoop to stealing a ‘Stupice’ or shoplift a ‘Mortgage Lifter!’ ;)

Last Year's Amazing 'Mortgage Lifter'

Back to the “how” end of things. First, tomatoes must reach a “mature” green stage before they can turn red. This tomato will be a good size for its variety, be light green, and have a pink to reddish color on the blossom end (bottom).

In this stage, the tomato produces an odorless, colorless gas called ethylene (same gas bananas emit). Ethylene is a growth hormone that causes green cells to turn red. Windy weather thwarts the ethylene gas by blowing it away from the fruit. This interrupts and slows down the ripening process.  Another weather factor is temperature. If weather is below 50 or above 85, the tomato will not produce the pigment cells that turn the tomato red (lycopene and carotene).

My Friend Anna in 2010, a Great Tomato Year!

Variety is the third number in the equation. Small fruited varieties (like cherry and grape tomatoes) normally turn red faster than large fruited varieties. Not all large varieties ripen at the same time, check for “days-to-harvest” before choosing a variety.  This number can be as low as 62 and as high as 100. Order seed catalogs or check online for this information. (Make sure the varieties do well in your area also ). And of course, characteristics like flavor and texture are important!

You can store mature-green tomatoes at 55-68 degrees F and they will eventually ripen. (this works for tomatoes that have fallen off the vine to early IF they are mature). For faster ripening, keep a small amount of fruit enclosed and add a ripe banana or apple. Temperatures over 77 degrees result in less red color and softer fruit. (Never store tomatoes in the refrigerator, the fruit will be tasteless).

If you are just DONE with tomatoes in your garden, you can dig up the plant (loosen it gently to keep roots intact). Shake off loose dirt, and hang the plant upside down in a protected area that meets the temperature requirements mentioned.

Here’s hoping next year is a better year for tomatoes!

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5 Responses to Why Aren’t My Tomatoes Turning Red?

  1. Lizeth says:

    I have a potted cherry tomato very tall and healthy, with at least 100 green tomatos, for over a month now.

    I coudlnt figure out why they are not turning red, after reading this artcile, it all makes sense, they are on a very windy porch, windy every day in the windy city of chicago.

    Well, I cant stop the wind, or they wont get any sun, thanks for the article, i thought my thumb was too green, and kept my tomatos green, boy was i glad it was just the wind.

    • Anne says:

      Hi Lizeth, I apologize I did not reply sooner, I’ve been locked out of my wordpress site! Glad to hear you figured out what was happening with your tomatoes. It sounds like you do have a green thumb but in a good way, ;-)
      Anne

  2. Holly Guenther says:

    I’m looking up green tomato recipes that don’t require frying them for the health factor.

  3. Beth C says:

    Mine are a little behind, but not too bad, I thought it was just b/c we got them in late =) I do mostly a Roma type for processing/etc. Our Celebrities are delish, but seem on the small side. But loving the cherry and Yellow Gold cherry! My children eat a whole basket at lunch =) Hope you are feeling better soon!

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