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4 Reasons Your Tomatoes Are Not Ripening + How You Can Help

Tomatoes not ripening? Here are the four main reasons why your tomatoes aren't turning red, and what you can do (if anything) to help ripen your tomatoes.

green tomatoes on vine

Why do tomatoes turn red?

Tomatoes turn red because of their lycopene content. What is lycopene? From Web MD (emphasis mine):

Lycopene is a naturally occurring chemical that gives fruits and vegetables a red color. It is one of a number of pigments called carotenoids. Lycopene is found in watermelons, pink grapefruits, apricots, and pink guavas. It is found in particularly high amounts in tomatoes and tomato products.

In North America, 85% of dietary lycopene comes from tomato products such as tomato juice or paste. One cup (240 mL) of tomato juice provides about 23 mg of lycopene.

Processing raw tomatoes using heat (in the making of tomato juice, tomato paste or ketchup, for example) actually changes the lycopene in the raw product into a form that is easier for the body to use. The lycopene in supplements is about as easy for the body to use as lycopene found in food.

People take lycopene for preventing heart disease, “hardening of the arteries” (atherosclerosis); and cancer of the prostate, breast, lung, bladder, ovaries, colon, and pancreas. Lycopene is also used for treating human papilloma virus (HPV) infection, which is a major cause of uterine cancer. Some people also use lycopene for cataracts and asthma.

How does it work?

Lycopene is a powerful antioxidant that may help protect cells from damage. This is why there is a lot of research interest in lycopene’s role, if any, in preventing cancer.

Note that our bodies find it easier to use lycopene once it's been heat processed. This is why I let my kids eat plenty of our homemade salsa, spaghetti sauce and ketchup.

So – no lycopene = no red tomatoes.

Reason #1 Your Tomatoes Don't Ripen = Time to Maturity

Each tomato variety has a time to maturity, i.e., days that it takes to ripen fruit from when the seed is planted. As a northern grower, I make sure to include some varieties that have a shorter time to maturity, along with some of the larger, longer season tomatoes.

If we get a particularly bad year, the short season tomatoes may be the only ones to have time for ripening on the vine, but usually they are simply the first tomato plants to give me ripe tomatoes for the season. As the season progresses, more varieties ripen.

Most tomato fruits ripen in six to eight weeks after blossoms pollination.

Some of my favorite short season varieties are:

  • Early Girl (hybrid)
  • Glacier (heirloom)
  • Stupice (heirloom)

Cherry tomatoes also tend to ripen sooner than larger fruited tomatoes.

tomatoes not turning red, not ripening

Reason #2 Your Tomatoes Aren't Turning Red = Temps are Too Cold

We ran into this problem in the summer of 2014. The spring was cold and wet, and the summer was cold and dry.

My friend, Tami, who busts her tail to start her seedlings early in her greenhouse and get them out in the garden as soon as absolutely possible, saw something she never saw before. Instead of getting red, her tomatoes stayed pink – but they rotted as if overripe.

She harvested all the pink, soft tomatoes and made some very ugly tomato salsa, but the flavor just wasn't very good.

As the season progressed, the tomatoes that did ripen were bland and flavorless. I took to picking them as soon as they started showing the first blush of color and bringing them inside to fully ripen, because the nights were so cool. The peppers were the same way. Full size, but they stayed stuck in the mature green stage until I brought them in to the counter, where they turned red in a couple of days.

Tomatoes give off their own ethylene gas to promote ripening, so there's no need to put them in a paper bag with an apple to promote ripening – unless you're really in a hurry.

Reason #3 Your Tomatoes Are Not Ripening = Temps are Too Hot

This year (2015), many area of the country are running into the opposite temperature extreme – it's too hot for the tomatoes to ripen. While tomatoes are generally heat loving plants, roasting heat is a problem. Cornell University Cooperative Extension notes:

The optimum temperature for ripening tomatoes is 70 to 75°F. When temperatures exceed 85 degrees to 90 degrees F, the ripening process slows significantly or even stops. At these temperatures, lycopene and carotene, pigments responsible for giving the fruit their typical orange to red appearance cannot be produced. As a result, the fruit can stay in a mature green phase for quite some time.

What can you do if you're stuck with green tomatoes and intense heat? Once the tomatoes have reached mature size, you can bring them inside to finish ripening. Remember, tomatoes like it 70-75 °F – just like many of us humans.

See Summer Gardens – Dealing with High Temperatures in the Garden for more tips on coping with extreme heat.

Never put your tomatoes in the fridge! Keep them at room temperature. With apologies to my husband's late great Uncle Bill, who worked on the railroad for many years and shipped tomatoes in refer cars – don't store tomatoes in the refrigerator.

Cold temps turns the sugars in the tomatoes to starch, ruining the flavor and making them mealy and bland. This is part of the reason many store tomatoes taste so bland. They are shipped in refrigerated trucks. Tomatoes stop ripening and don't rot, but the flavor is subpar.

Reason #4 Your Tomatoes Aren't Turning Red – They're Not Red Tomatoes

With the growing popularity of heirloom tomatoes, there are many varieties now available that simply do not turn red, even when ripe. Tomatoes varieties may ripen to pink, orange, yellow, purple – even green. If you're trying a new variety of tomatoes, make sure you know what the mature stage is supposed to look like, so you don't miss out on the yumminess.

For instance, when I first tried garden peach tomatoes, I gave a plant to my mom. She didn't tell my stepdad what she was growing. He saw the thin skinned, lightly fuzzy tomatoes in the garden, and thought they were sick. He picked the ripe tomatoes and tossed them out.

Mom went looking for her tomatoes and found them gone. They got it sorted out, but she had to wait a little longer to try the tomatoes.

Since I plant several different colors, I always note which plant is where on my garden charts. I also take care not to place plants that have similar size fruit but mature to orange and red next to each other, so I'm not mistaking underripe red fruit for ripe orange fruit.

How to Tell When Green Varieties of Tomatoes are Ripe

I've been growing Green Zebra tomatoes for a number of years, because the flavor is excellent and they usually produce a good crop here. As the name implies, they ripen green with stripes. As with other green varieties I've tried, you can tell they are ripe because the underlying color of the green tomato turns more yellow/golden instead of white/lighter green when they've reached full maturity. The flesh turns soft and juicy.

Ripe green zebra tomato

2020 Possible Factor – Wildfires?

I've noticed this year that my tomatoes are struggling to ripen even when other conditions are right.

A reader contacted me recently and was talking about shifting sunlight affecting plant growth. (The sun goes through cycles and the lighting shifts over time.)

This got me thinking about how the smoke from wildfires is spreading over large areas of the planet.

Obviously, this does impact the sunlight hitting (or not hitting) the ground. I haven't seen any studies on this yet, but it seems likely this could affect ripening.

One study I did find indicated that increased levels of CO2 can interfere with ripening. They tested higher levels than we would normally see, even with smoke.

If smoke is thick, it can clog the stomata in the leaves of the plants, and interfere with respiration. This could stress the plant and slow down ripening.

I'm curious if anyone else has run into this phenomenon.

When Your Tomatoes Finally Do Get Ripe…Or If They Don't

Check out these recipes that will help you enjoy your harvest year round!

Yes, Green Tomatoes are Safe to Eat!

Also, if your tomatoes refuse to ripen, green fruits are safe to eat. Just process them in some way before eating, such as cooking or pickling. We turned the green tomatoes knocked off our plants during a hail storm into green tomato pickles (recipe here).

Other Reasons For Strange Colored Tomatoes

Sunscald – Light colored, leathery patches, generally found on the top or side of the tomato, may be sunscald. Sunscald is due to intense sun exposure. If not spoiled, the rest of the tomato may be used. Sometimes the scald leads to rot.

Soil Fertility IssuesCornell University Cooperative Extension notes, “high levels of magnesium and low levels of potassium can lead to conditions like blotchy or uneven ripening or yellow shoulder disorder.”

Blossom End Rot – When the blossom end of your tomato fruits has a small or large black lesion, this is blossom end rot. It's linked to low calcium availability in the soil, so adding calcium during planting may be helpful for avoiding it.

BUT – even when there is calcium in the soil, too much or too little rain can make it unavailable to the plants. Regular, even watering is best. Read “7 Steps to Stop Blossom End Rot” for more on the causes of BER and how to prevent and control it. 

For more tips on dealing with excess rain, see Too Much Rain in the Garden – Managing Wet Dirt and Waterlogged Plants.

Extreme case of blossom end rot on tomato

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Unripe tomatoes on vine

Originally published in 2015, last updated in 2020.

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  1. I put all of my green tomatoes at end of season in an open cardboard box. They all ripen for some reason not sure why.

    1. The goal of a tomato plant is not to make yummy tomatoes for us to eat, but to reproduce. To reproduce, they need to mature fruit. This means that if a fruit is close to maturity, it will do its best to ripen, provided that other factors aren’t interfering with ripening.

      The focus of the article is more on the factors that keep fruit from ripening on the plant when they should be doing so. I collect all reasonably filled out fruit at the end of the season and place them in cardboard trays to ripen, too.

  2. Thanks for these ideas to think about and apply a remedy to. Here are a couple tricks I’ve found or heard that work, to ripen tomatoes at the end of our short cooler growing season. I water the plants less, about the end of August/first of September. It seems to put the plants under a little stress and encourage them to ripen all at once.

    A friend said she bends the stems over at the bottom of the plant and the tomatoes begin to ripen too, something her seasoned gardening father-in-law taught her. It may be the same idea of less water or a little stress.

    I have also cut off or pulled up very productive stems or plants and hung them upside down in my shed or garage. I can usually get a few more ripe tomatoes throughout the month or tow.

    Lastly, I have learned it’s ok to take the plants out, after trying to extend the season with plastic for a few weeks. Sometimes the prospect of cold rain or cold garden clean up is enough to say it’s time to end even with green tomatoes and look forward to learning and trying another way next Summer. 🙂

  3. I am in San Diego, California and it is taking *forever* this summer for my tomatoes to ripen. I grow Purple Cherokee and Japanese Trifele, and this year we are having to deal with heat waves (100+ degree weather for days) as well as wildfires. They are still flowering and setting fruit this late in the season, and overlapping with my Stupice. Let’s see which one will give me mature fruit first.

  4. End of September 2020 here in Utah and not one of my larger tomatoes has ripened. The cherry tomatoes have, but I’m likely stuck bringing them in to ripen on the counter. I was wondering if the fires had something to do with it because we haven’t had a single clear sky day in probably a month or more.

    1. As I said, I haven’t seen any official studies, but I can see with my own eyes that the sky here is filled with haze, and the tomatoes are so very slow to ripen this year. We’re much farther away (Wisconsin), but I can see the difference.

    2. I know this comment is a year old but thought id mention anyway, smoke can obstruct 50% or more of UV rays so it definitely can be a reason why things are not growing & ripening as usual!

  5. Thank you! I now know the most possible reason why my entire garden isn’t faring well – heat overload! I’ve noticed sunscald on my squashes, tomatoes are staying green, and I know i’ve used a lot of compost in there and watered enough too. Oh, and my squash plants seem to be dying off in August.

  6. Thank you so much! Your post really helped me narrow down the reason why we’ve been staring at green tomatoes for a couple of weeks (or more!). It’s been “one hot summa, don’tcha know?” Yes, I’m mixing New England and Midwest dialects. Gosh, I sometimes I really miss the Midwest. I lived in Minnesota for a few years, and worked with more than a few people from Wisconsin. I hope you’re staying healthy and safe.

    1. You’re welcome, and I hope the weather gets a little more cooperative through the rest of the gardening season. We could use some rain here, as most of the recent storms have been tracking north or south of us.

  7. I didn’t read all the posts so someone may have covered it. You can pick green tomatoes and put them in a brown paper bag and into the pantry. Check every day to find those that ripened in the bag.

  8. Where do you find tiger nuts? I have lived in upstate N.Y. for 49 years and I have never seen a tiger here. Do I half to order from Africa?

    1. Thankfully, no tigers, testicles or other nuts are involved in the harvesting of tiger nuts, as they are a root vegetable with a good PR agent. I usually order a bag of Anthony’s tiger nut flour from Amazon (link).

  9. Hi

    Early Girl Tomatoes
    I noticed that two plants had a lighter shade of Green leafs while the other had a darker shade of leaf
    having the same prolem with tomatoes not turning full red.

    inside is white and the outside is light red
    we had a heat wave for two weeks above 90
    I picked all and placed them in a brown bage going to put an apple the apple does not have to be cut ?
    thanks for your help

    1. Tomatoes generate their own ethylene gas, so you don’t really even need the apple. If you want to speed things up, go ahead and use the apple, but don’t cut it open. That will just make the apple and tomatoes more likely to spoil and potentially attract fruit flies.

  10. Last year in southeast PA was a disaster because of all the rain; it was a little cool also, but the rain rain rain left me with diseased plants and a few mushy tomatoes. This year has been pretty wet also, but not as bad. But it has been hotter than the past several years, and the tomatoes don’t seem to be ripening as well. The big ones just sit, and even the cherry tomatoes we grow, which usually turn a bright red, almost seem more orange or even a little bronze-like this year, and the taste is just not quite as good. So I finally went out on the internet, and came upon your site. Thanks for confirming that the hot weather can slow down ripening. I knew it can slow or even stop fruit set, but your very helpful article seems to confirm what I am seeing about the ripening.
    Location: Southeast PA (Bucks County)
    Varieties: Park’s Nectar, Supremo, Celebrity, Paul Robeson, San Marzano Redorta

    1. We tend to think of tomatoes as heat loving, and they are – to a point. Just like most crops, they have their “sweet spot” when it comes to temperature. They may do okay outside the range, but won’t thrive.

      Thanks for sharing your experience, Mark.

  11. I have big boy and big beef steak tomatoes plants planted. This is my first time. I have both planted in large pots. They’ve been planted for 21 days and have different sizes of tomatoes on them but all are green. Not sure how big they are suppose to get before they are developed or if they are suppose to still be green. I planted the plant not the seeds. should I keep waiting or pick one and bring inside? Please help. Thank you!

    1. Be patient. Both Big Boy and Big Beef Steak produce fairly large tomatoes, so they may have some growing left to do. The estimates to fruiting are just that – estimates. Growing conditions can slow down or speed up ripening.

      When tomatoes are ready to ripen, before they turn red, they will turn a slightly lighter shade of green. Once you’ve seen it, you’ll know what to look for in the future.

  12. I have a few questions from this years tomatoes.
    1. I have found a few during this growing season with no seeds inside. Does that mean they were overripe? They tasted fine.

    2. Some this year were very green and slimy around the seeds. They did not smell good. I didn’t eat those. What did that mean?

    Thanks so much for your help and time.

    1. I know that no seeds is not a sign of overipeness. Different varieties of tomatoes have different amount of seeds, and tomatoes will also set more or less seeds under different growing conditions. Some tomatoes are now even being advertised as “seedless”.

      As for the inside issues, research did not turn up much. I suspect some sort of fungal issue promoting spoilage, given the description. Our neighbors had a similar issue this season due to heavy rains during harvest time. They do not trellis their fruit, and much of it was in direct contact with the ground. We trellis our tomatoes, and did not have similar issues, although we still had foliage stress and splitting from the heavy rain.

      You may want to consider trellising, if you don’t use it, and inoculating your garden with bacteria to help crowd out the bad bacteria. There’s more on EM-1 and other helpful bacteria (plant probiotics) in this post –

    1. I’m not sure what the problem may be. I tried an online search, but didn’t come up with anything that specifically mentioned soft fruit and no other symptoms.

      Has it been very wet in your area? Excess moisture can make fruit soft. Have you grown this variety before? If not, perhaps it’s naturally a softer fruit. That would be odd, but it’s possible.

  13. I planted organic Roma tomatoes this year. We had a hail storm early in the year that made my poor little plants look like sticks, but I tended to them like babies and they have grown like champions. Now I have a bunch of tomatoes, but they’re not ripening. I’m going to try the paper bag with an apple method, but someone told me they weren’t ripening because I’ve planted jalapeno peppers in the same raised bed. Could the peppers be the cause for the tomatoes not ripening?

    1. I’ve never heard of that, and I’ve had peppers and tomatoes planted right near each other in the past with no issues. Maybe they’re simply running late because of the stress earlier in the season?

  14. Hi, thanks for the article! I suspected my bumper crop of tomatoes wasn’t ripening due to a record-breaking cold spring/summer here in South Dakota, but wanted to be sure.

    Here’s a trick for “hot housing” your own tomatoes. Go ahead and pick them when they’re full-size, and put them in a large paper bag with an apple or a banana. These two fruits give off huge amounts of natural ethylene gas and will encourage your tomatoes to ripen. Once your tomatoes have some blush, you can remove the apple/banana or leave them to speed ripening. You’ll sacrifice that fruit, but you’ll have ripe red tomatoes!

  15. superb article. my tomatoes are superb on the vine totally green hanging in bunches ready to ripen.
    however we have had quite an exceptional couple of months with very hot sunshine taking the temperature well over the norm. I am hoping that it is the temp. that is causing all the problems. everything else is perfect.