What causes sour tomatoes and how can you fix it

I love picking and eating tomatoes fresh out of the garden. But every once in a while, you come across one that just doesn’t taste right. Tomatoes are supposed to be flavorful and sweet, not bland and sour. In this post, I am going to look at what causes sour-tasting tomatoes and, most importantly, how you can fix it.

How can you fix sour tomatoes? The best way to improve the taste of your tomatoes is to ensure they get enough sunlight. Try to lengthen the ripening process, by providing optimal conditions for your plant and stop watering a few days before you plan to harvest your tomatoes

To get a better understanding of how to fix sour tomatoes, let us look at what causes it in the first place.


Why do some tomatoes taste sour

The most important factor for good-tasting tomatoes is a balance of sweet and sour. A lack of sugars (fructose and glucose) or a disproportionate amount of acids (citric, malic, and ascorbic acid) will cause a sour-tasting tomato. Genetics plays a considerable role in determining the taste of the fruit. I covered the topic of why homegrown vegetables taste better in one of my recent posts if you want to know more about this. But what can you do if a normally sweet-tasting array of tomatoes taste like biting into some sour candy?


Soil ph plays a role

Tomatoes prefer a slightly acidic soil ph around 6.0-6.8. Ph-levels can be increased by applying lime or decreased with sulfur. The acidity of your soil is more of an indicator of unfavorable conditions and doesn’t per se cause any issues. Alkaline soil reduces the availability of essential nutrients (iron, phosphate, manganese). This can be detrimental when your soil is already low in these Minerals, so let’s look at why soil nutrients are so important for the flavor of your tomatoes.


Soil nutrients are important

Tomatoes get their sweet flavor through photosynthesis. Once a Tomato grows on the plant, sugar will be transported into the fruit via Phloem. However, the plant will first condense simple sugars (Fructose & Glucose) into Starches. By the way, this is the reason ripe fruit tastes so good; if a plant would just pump simple sugars into its fruit, they would be no sweeter than its leaves. At some point, the ripening process starts; this means enzymes get activated and begin to break down these starches back into simple sugars. In most cases, this is caused by changes in the environment or exposure to ripening agents like ethylene gas.

Lush green leaves help the plant to produce more sugars and store them in its fruits. And that’s where the soil nutrients play an essential role. The better the growing conditions are for your plant, the more sugars it will produce. Photosynthesis requires both healthy leaves as well as lots of sun exposure.


Do your tomatoes get enough sun

Tomatoes love the sun; they really can’t get enough of it. I try to expose my Tomatoes to both morning and afternoon sun, to ensure maximum photosynthesis can take place. I only avoid direct, scorching hot, noon sun. So more is better when it comes to sun and tomatoes, but a minimum of 8 hours will do.

Now with all the basics out of the way, let’s look at a couple of tips and tricks to make your tomatoes sweeter.


Sure-fire ways to make Tomatoes taste sweeter

The question remains, what can you do when you still have sour tomatoes, after making sure the growing conditions are right?

The most efficient step to enhance the flavor of tomatoes is to water them less. Once your tomatoes start to ripen reduce the amount of water you give them by half; this will not only prevent them from splitting but also improve their flavor. Here is my recent article about cracks in Tomatoes, if you want to know more.

Another way to sweeten up your tomatoes is to lengthen the time sugars are transported into the fruit. This process takes place before the fruit begins to ripen, so the longer the plant is in favorable conditions, the better. (lots of sunlight, enough nutrients in the soil and regular watering). One way to reduce the overall stress of a plant is to prune it. There should be no leaves below the first fruit cluster, to prevent serious issues with blight. I recently wrote a whole article about it here. Furthermore, make sure only to grow one main stem. To achieve a single stem tomato, you have to remove all tomato suckers that grow in the junction between the stem and a branch. You will reduce the number of your tomatoes you grow in total, but this helps to improve their quality.

On the same note, spacing your tomatoes is also essential. Give your plants some space to breathe and leave at least a 20″(50cm) gap between them.

I already mentioned that genetics play a significant role in the taste of the tomatoes. In general, smaller tomatoes are sweeter; I find yellow ones are often the sweetest out of them all. Some examples (both red and yellow) are Sungold, Sakura, Rosada, Golden Sweet, and Sun sugar.


Don’t fall for useless hacks

Adding sugar to your soil will not translate into sweeter tomatoes, nor will it help the plant in any way. Most likely, the sugar is simply washed away by rain or, in the worst case, attracts some bacteria. I don’t know how this gardening Tip started, but usually, plants don’t absorb sugar through their roots.

Companion Planting is excellent and has many benefits. Sadly enhancing the sweetness of Tomatoes isn’t one of them. It’s sometimes rumored that growing Basil next to Tomatoes does make them sweeter, but so far, there is no actual proof this is the case. This study examined the effects of companion plants on tomatoes and came to the conclusion taste was not affected. Nonetheless, companion planting is a fantastic practice that can help with all sorts of other issues.


Related Questions

Can you improve the flavor of harvested tomatoes? There are a few ways to make them taste better, but generally, it’s easier to enhance the taste of tomatoes that are still on the plant. First, make sure only to wash your tomatoes when you actually want to eat them, because they can still absorb some of the water, diluting the taste in the process. Second, you can place unripe tomatoes in a box together with an apple to expose them to ethylene gas; this helps to break down the starch into simple sugars. If this doesn’t do the trick, sprinkle some sugar & salt on the tomatoes before you eat it.

Does cold weather affect the taste of tomatoes? Yes, it does. Extended periods (more than three days) below 5°C will permanently alter the flavor of your vegetables. This is true both before and after harvest, so make sure your plants stay warm and cozy in colder nights.