Why Are My Tomatoes Deformed? (Common Causes & Fixes)


When you grow tomatoes, the fruit doesn’t always form perfectly.  Sometimes, there will be something wrong with the color or the shape, or there will be damage to the fruit.

So, why are your tomatoes deformed?  Tomatoes will grow deformed due to environmental factors (such as water, temperature, or sunlight), genetic factors, pests, and diseases.  Deformed tomatoes may have cracks or splitting, zippering, catfacing, uneven ripening, holes, or spots.

Of course, there are ways to prevent some of these problems.  The method you use will depend on the problem your tomatoes have.

In this article, we’ll explore how tomatoes can be deformed and what causes these issues.  We’ll also take a look at how to prevent these problems in the first place.

Let’s begin.

Why Are Your Tomatoes Deformed?

Tomatoes can become deformed for several reasons.  Some of the most common reasons are environmental issues, such as:

  • Uneven watering
  • Extreme temperatures
  • Too much or too little sunlight

However, there are other causes of deformed tomatoes, such as pests and diseases.  Even genetics (that is, the type of tomato) can make it more or less likely that your fruit will be deformed.

There are lots of tomato deformities you might see, including:

  • Cracking and splitting
  • Zippering
  • Catfacing
  • Uneven ripening
  • Holes
  • Spots

Let’s start off by taking a look at a fairly common one: cracking and splitting.

Cracking and Splitting Tomatoes

New and experienced gardeners alike will probably see some cracked or split tomatoes in the garden every year.  This problem is common, but what causes tomatoes to crack and split?

cracked tomato
This tomato is cracked, probably due to a lack of water followed by too much water.

Well, according to the University of Massachusetts Extension:

“Water uptake, humidity, temperature and soluble solids (sugars) as well as calcium nutrition and standing water on the fruit are thought to have roles in fruit cracking, along with genetics.”

https://ag.umass.edu/vegetable/fact-sheets/tomato-fruit-cracking

Water uptake is one of the most important factors that will cause tomatoes to crack and split.  According to the North Carolina State University Extension:

“Cracking and splitting occur when rapid changes in soil moisture levels cause fruits to expand quicker than the tomato skin can grow.”

https://pender.ces.ncsu.edu/2020/03/what-causes-tomatoes-to-crack/

This is much more likely to happen when there is a drought (extended period of dry weather) followed by heavy rain or irrigation.

There are two basic types of cracking that you will see in tomatoes:

  • Radial cracking – this type is more serious, and it involves vertical splits running up and down the tomato (from stem to blossom end).  This type of cracking is more likely in hot and humid weather.  The cracks tend to be deeper than concentric cracks, and rot is more likely.
  • Concentric cracking – this type of cracking involves circular cracks around the top of the tomato (near the stem).  The cracks tend to be superficial, and may not lead to rot.

Cracking and splitting is more likely to occur as the fruit begins to ripen.  However, green fruit can also crack and split.

If green fruit does crack, then it will most likely rot before ripening.  In that case, it is probably best to pick off any green fruit that is cracked.

That way, the plant can focus on sending its energy to healthier fruit.  If you want, you can compost the fruit or feed it to your chickens instead of throwing it away.

To prevent your tomatoes from cracking and splitting, provide them with consistent moisture.  Keep an eye on the weather forecast, and avoid watering right before or after a heavy rain.

If the forecast calls for extended hot and dry weather, plan to water more often to keep the soil moist.

rain
If the weather forecast calls for rain, avoid watering right before the storm!

In addition, keep your tomatoes from getting too hot in the middle of summer.  If temperatures begin to soar, you can use overhead irrigation (such as from a sprinkler) to cool tomato plants.

You can also use a shade cloth or row cover to give your plants shade during the hottest part of the day (midday).  This will keep them a little cooler and help to prevent the problem of sunscald (more on this later).

Finally, you can try planting tomato varieties with resistance to cracking.  According to the University of Iowa Extension, a few crack-resistant tomato varieties include:

  • Jetstar
  • Mountain Spring
  • Mountain Fresh

Zippering on Tomatoes

Zippering is a tomato deformity that looks like a long brown scar, running up and down the fruit (stem to blossom end).  A single fruit may have more than one scar (the scar really does look like a zipper!)

zippered tomato
This tomato is zippered and also has some holes to go along with it.

Zippering is mainly a cosmetic issue, and it does not affect the flesh inside or cause the fruit to rot.  In some cases, a hole appears near the scar.

According to Cornell University, zippering occurs when the flower anther (the part that makes pollen) sticks to the developing fruit as it grows.  You can see pictures of zippering of tomato fruit on the Cornell website.

Zippering is more likely in cool temperatures. Genetics also plays a role, and some tomato varieties are more likely to display zippering.

Since zippering is cosmetic and does not lead to rotting fruit, there isn’t much point in trying to prevent it from happening.  If you do get some tomatoes with zippering, you can always cut away the skin and use the flesh to make tomato sauce for pasta or pizza.

Catfacing on Tomatoes

Catfacing is another type of tomato deformity that causes scarred and misshapen fruit.  The affected fruit will have sunken, hard spots that are gray or brown.

These spots will sometimes go deep into the tomato, almost like holes.  According to the University of Massachusetts, catfacing and the holes that come with it can increase the chances of infection by fungus, such as black mold.

There is not much research on the problem of catfacing.  However, it is suspected that catfacing is more likely when young tomato plants are exposed to cold.

According to the University of Massachusetts:

“Cold temperatures during flowering have been shown to increase incidence of catfacing, as have extreme fluctuations in night and day temperature. Under some conditions, pruning and high nitrogen levels can increase incidence of the disorder. Additionally, damage from thrips to the side of the pistil of flowers can cause catfacing.”

https://ag.umass.edu/vegetable/fact-sheets/tomato-cat-facing

To avoid catfacing of tomato fruit, transplant your tomatoes into the garden late enough to avoid cold weather and frost in the spring.  You can check the frost dates in your area with this tool from the Old Farmer’s Almanac.

frosted leaf
Wait until the danger of frost has passed to transplant tomatoes into the garden.

In addition, you can try planting smaller tomato varieties to prevent catfacing.  According to the University of Minnesota Extension, small tomatoes are less likely to get catfacing.

In my experience, I have seen catfacing on large heirloom tomato varieties, but never on cherry or grape tomatoes.

If you do get any green fruit with catfacing, remove it and compost it.  That way, the plant can save its energy for normally developing fruit.

Pointed Ends on Tomatoes

Sometimes, you will see deformed tomatoes with pointed ends.  However, this is not a cause for concern, since the fruit will still be edible.

Pointed ends on tomatoes can be caused by genetics.  Some tomato varieties will naturally have points at the bottom (blossom end).

It is also possible that you got a mislabeled tomato plant at the garden center.  In that case, you could end up with pointed tomatoes, even if you were expecting something else!

Finally, you may also see strange points or deformed sections on your tomatoes if they grow up against something, such as:

  • The vines or branches of the tomato plant itself
  • The support for the tomato plant (stake, cage, or trellis)
  • The twine used to tie the plant to the support

If you don’t like the look of these deformed tomatoes and can’t stand to eat them raw, just cut them up and use them for tomato sauce instead.

Green or Yellow Ridges (“Shoulders”) on Tomatoes

Sometimes, tomatoes will suffer from uneven ripening.  This condition is common at the top (stem) end of the tomato, and is sometimes called:

  • Green shoulder
  • Yellow shoulder
  • Yellow eye
  • Yellow tag
green shoulders on tomato
This tomato has green shoulders on top, due to too much chlorophyll and not enough red pigment!

No matter the name, the problem is the same: uneven ripening of fruit.  An unripe tomato will have yellow (or in extreme cases, green) ridges or “shoulders” at the top of the fruit.

So, why do tomatoes get yellow or green shoulders on top of the fruit?  It has to do with chlorophyll (the substance that makes plants green and helps them to produce energy by photosynthesis).

Normally, the chlorophyll in green tomatoes will break down over time, later giving way to reddish and orange pigments.  However, according to the University of Connecticut, this sometimes fails to happen:

“Green chlorophyll in these regions fails to develop red pigment. This happens very early in fruit development.”

http://ipm.uconn.edu/documents/raw2/html/871.php?aid=871

According to the University of Massachusetts, potassium may play a key role in this problem:

“Severe cases of blotchy ripening and yellow shoulder are most often associated with factors that limit the supply of potassium to maturing fruit.”

https://ag.umass.edu/vegetable/fact-sheets/tomato-physiological-ripening-disorders

To avoid this problem, make sure that your tomato plants get plenty of potassium so that the fruit can ripen properly.  You can learn more about potassium deficiency in plants in my article here.

Holes in Tomatoes

If there are holes in your tomatoes, then the most likely cause is pests.  Holes in tomatoes could be caused by animal pests, such as woodchucks, squirrels, and birds.

bird bath
Birds may go after your tomatoes if they get thirsty – a birdbath might prevent this problem.

However, the cause could also be insect pests, such as:

tomato hornworm
Tomato hornworms are just one type of worm that eats tomato plants.

Black or Brown Spots on Tomatoes

Black or brown spots on tomato plants are often caused by blossom end rot.  Blossom end rot is caused by a lack of calcium, due to:

  • uneven watering
  • too much nitrogen, potassium, or magnesium
  • root damage
  • calcium deficiency in soil
tomato blossom end rot
Blossom end rot causes brown or black spots on the bottom of tomatoes.

Blossom end rot is more likely to affect the first fruit of the season.  Once blossom end rot takes hold, it becomes more likely that fungi and bacteria will invade the fruit and cause it to rot.

To learn more, check out my article on blossom end rot and how to avoid it.

White, Gray, or Tan Spots on Tomatoes

If you see white, gray, or tan spots on your tomatoes, then they are probably suffering from sunscald.  Sunscald affects the fruit of tomato plants when they are exposed to strong sunlight over a long period of time.

sunscald on tomato
A tomato will sometimes get sunscald if there are not enough leaves on the plant to shade the fruit from the sun.

Sunscald is common on the fruit of plants that are losing their leaves due to pests or diseases.  Plants that are over pruned will also be more susceptible to sunscald (since there are fewer leaves and branches to shade the fruit!)

Sunscald causes a tough, leathery patch of white, gray, or tan to appear on the surface of the tomato fruit.  According to the University of Minnesota, the sunscald spot may eventually succumb to fungi or bacteria that will rot the fruit.

For example, anthracnose is one type of fungus that affects tomatoes.  According to the University of Illinois Extension:

“Circular sunken lesions develop on fruit. Over time these spots will enlarge and darken. Often pink to orange masses spores form in concentric rings on the surface (when it’s humid). Anthracnose may occasionally be found on leaves and stems where it will cause irregularly shaped brown spots with dark brown edges.”

https://extension.illinois.edu/blogs/good-growing/2020-05-01-troubles-tomatoes

Conclusion

Now you have a much better idea of why your tomatoes are deformed.  If you are able to diagnose the problem and the cause, you might be able to prevent it from happening in the future.

I hope you found this article helpful.  If so, please share it with someone who can use the information.

If you want to read some of my most popular posts, check out the “Best of GreenUpSide” page here.  Enjoy!

~Jonathon

jonathon.david.madore

Hi, I'm Jonathon. I’m the gardening guy (not guru!) who is encouraging everyone to spend more time in the garden. I try to help solve common gardening problems so that you can get the best harvest every year!

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