Tomato gardeners end up asking themselves a lot of questions over the course of the growing season. Like “what are these weird bugs all over my plants?” and “why do my tomatoes disappear every time my kids play outside?” Another common question is “why are my tomatoes turning yellow instead of red?” When you’re expecting deep ruby gems and all of a sudden they’re blotchy yellow (or completely golden!), it’s bound to cause some distress.
Fortunately, there are some easy answers as to what may be causing the discoloration.
Why are My Tomatoes Turning Yellow Instead of Red? What’s Wrong with Them?
First and foremost, they might have a sunburn.
You see, red tomatoes contain high amounts of lycopene, which is what gives them their beautiful color. It’s a carotenoid rich in antioxidants, and is also present in other red and pink fruits and vegetables. You’ll find it in red peppers, watermelon, beets… you get the idea. Tomatoes also contain carotene: the pigment that gives carrots and peppers orange and yellow hues.
Different growing conditions will activate different chemicals within plants. When growing tomatoes, the best temperature range for them to ripen to perfection is 70 to 75 F (which is 20 to 25 C). Although tomatoes love sunshine and heat, you can have too much of a good thing.
Related Article: Why do Tomatoes Turn Black on the Bottom, on the Vine?
Tomato ripening slows—and can even stop—if the temperature gets too hot. Basically, if it’s a particularly hot, sunny summer, and your tomatoes are ripening in 85 to 90F heat (that’s 30 to 35C), they’ll go into a sort of torpor. The plants cannot produce lycopene properly, and even carotene production suffers. If the sun is hitting your tomatoes really hard, they’ll end up with sunburnt shoulders: the tops will be yellow, while the lower parts will be reddish.
Too Much Cold Can Yellow Them Too
Similarly to how excessive heat can damage your tomato fruits, too much cold can hurt them as well.
Remember how there’s a magical middle temperature range for tomato ripening? If your plants have matured too late in the season, they might be exposed to less-than-ideal conditions during the day. Sure, things might be sunny and hot at midday, but what about in the morning and late afternoon?
If the temperatures are too cold, then those magical pigments can’t activate either. Your tomatoes will mostly stay green, but will creep into yellow range as they try weakly to ripen on the vine.
How to Avoid These Issues
Do thorough research to determine various average temperatures in your area. If you know that you’ll have a few solid weeks of ideal temperature in mid August, for example, then you can plan your planting. Look at your seed packets to see how many days it’ll take for your tomatoes to reach maturity.
This way, you can plan your tomato garden so the fruits will ripen in that magic zone.
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If you’re planting them in a super-sunny spot, allow the leaves to grow in densely. This leaf cover will protect the fruits from intense sunlight as they mature. Alternatively, if you live in a really hot climate, you might want to provide your plants with some afternoon shade. Gardeners in really hot areas can also try to find heat-resistant tomato seeds. These fare much better in scorching conditions! Try to get seeds from tomato plants that thrive in Florida, Arizona, southern California, and Texas, as they’ll likely do well for you.
Water early in the morning and late in the afternoon, always at soil level. If you water from overhead, the droplets can act like little magnifying glasses. This means that water + sunlight will burn your plants (and their fruits) instead of hydrating them.
Or, You Might Just be Growing Yellow Tomatoes
Have you taken all the actions mentioned above and your tomatoes are still golden instead of red? Then there might be a possibility that you’re growing a yellow variety.
Remember that tomatoes come in dozens of different hues. Not only can you grow red or reddish-orange varieties, but you can also find them in every shade of purple, black, green, pink, striped, and multi-hued. These can grow in any size from teensy, half-inch currant tomatoes to massive multi-pounders. Consider that there are over 10,000 different tomato cultivars that we know of so far, and you can only imagine how many different hues you can grow!
Random mutations that cause different colors to evolve can result in some spectacularly tasty fruits. For example, the Napa Champagne yellow cherry tomatoes are mutations from a pinkish blush cultivar. This means that someone planted some seeds expecting to harvest pink tomatoes, and ended up with silvery yellow ones instead. There’s nothing wrong with them: in fact, they’re some of the most delicious cherry tomatoes available. But you can imagine how distressed the gardener must have been when their expected fruity babies seemed to be suffering from some horrible nutrient deficiency!
Here’s Another Delicious Mutation to Explore: What Does Yellow Watermelon Taste Like?
Hopefully this article has helped you out! Now, the next time a friend reaches out asking “why are MY tomatoes turning yellow instead of red?”, you can pass your wisdom along to them in turn.
(And if it turns out they’re actually growing a new cultivar of something tasty, ask them for some seeds.)