Why Do My Tomatoes Have Tough Skins? (Causes & Solutions)


Fresh tomatoes grown in your own garden are great to have.  However, they are not as enjoyable when they have tough skin. 

So, why do your tomatoes have tough skins?  Tomatoes can develop tough skin due to excessive heat, intense sunlight, or certain diseases such as anthracnose and curly top virus.  Certain tomato varieties, such as Roma or plum tomatoes, are bred to have thicker skins to resist damage from insects.

Although there are lots of ways that tomatoes can develop tough skins, there are also ways to prevent it from happening.

In this article, we’ll talk about why tomatoes have tough skins and how to prevent tough skins on tomatoes.  We’ll also talk about what you can do about tomatoes with thick skins if you have already harvested them.

Let’s get going.

Why Do My Tomatoes Have Tough Skins?

There are several different reasons that tomatoes can develop tough skins, including:

  • Excessive heat (along with dry weather)
  • Intense Sunlight (tomatoes can get sunburn!)
  • Diseases (Anthracnose or Curly Top Virus)
  • Variety (some are naturally thick-skinned)

Let’s start off with heat, since this is a common cause of tough tomato skins.

Tough Tomato Skins Caused by Heat

In some cases, tomatoes will develop tough skins in response to environmental conditions.  This is one way the tomato fruit defends itself against the elements.

According to the New Mexico State University Extension, hot and dry weather sometimes leads to tough skin on tomato fruit, making it almost like leather.  Although the fruit may ripen completely, the skin will be thick in response to high heat, lack of water, or a combination of the two.

In other cases, extreme heat will cause the fruit to ripen unevenly or incompletely.  The ideal temperature for ripening tomatoes is 70 to 75 degrees Fahrenheit (21 to 24 degrees Celsius).

tomatoes on stem
If tomatoes do not ripen evenly and completely, the result may be some areas with thick skin.

When temperatures rise into the 80’s and 90’s Fahrenheit, tomato ripening slows down quite a bit.  You can learn more about why tomatoes fail to ripen in my article here.

To avoid thick skin due to dry soil, keep your tomato plants watered.  Apply mulch over the soil to help retain moisture, if necessary.  A drip irrigation system can also help to keep soil moist but not soaking wet.

Another cause of thick skin is lack of proper ripening.  This leads to tough spots on a tomato’s skin.

This is especially common on the top part of the fruit.  You can sometimes see this as green or yellow “shoulders” on the top of the tomato.

According to the University of Missouri:

“These yellow areas never ripen properly and the tissue below them is tough and poorly flavored.”

https://ipm.missouri.edu/meg/2012/8/Hot-Weather-Tomato-Problems/

This happens when chlorophyll (which makes tomatoes green at first) is not replaced by lycopene and carotene (which are pigments that make tomatoes reddish-orange).  When it is too hot, tomatoes stop producing lycopene and carotene, so they slow down or stop the ripening process.

green shoulders on tomato
Green shoulders on a tomato occur when the top part of the fruit ripens more slowly than the rest of the fruit, sometimes due to heat from sunlight.

Think about immature green tomatoes versus ripe red tomatoes.  The red ones tend to be softer, whereas the green ones tend to be firm.  A lack of proper ripening caused by excessive heat will leave your tomatoes with thick skin.

To avoid excessive heat for your tomato plants, try giving them some shade during the hottest part of the day.  You can do this with shade cloth, which can provide 10 degrees Fahrenheit (6 degrees Celsius) or more of heat protection.

You can learn more about shade cloth in my article here.

Tough Tomato Skins Caused by Intense Sunlight

Intense sunlight can also lead to tough skin on your tomatoes.  One way this happens is when strong sunlight raises the temperature of the fruit itself.

As mentioned earlier, excessive heat can lead to tough skins on tomatoes, and intense sunlight makes this problem even worse.

Intense sunlight can also cause direct damage tomato skins by burning them.  This condition is called sunscald, and it is similar to the way we can get blisters from sunburn.

sunscald on tomato
This tomato has been burned with sunscald (the withish-tan spot on the skin).

According to the University of Maryland Extension:

“Large, light-colored blistered areas develop on the sides of fruits facing the sun.”

https://extension.umd.edu/hgic/topics/sunscald-vegetables

The blistered areas caused by sunscald are white or tan, and they become a tough spot on the skin of the fruit.

According to Purdue University, sunscald is more likely on tomato plants that were over pruned or whose leaves were damaged by insects or disease.  Without enough leaves to block out some of the sunlight, these plants become more susceptible to sunscald.

As mentioned earlier, shade cloth is a good way to protect tomato plants from the sun and heat in the height of summer.

You can find knitted 30% shade cloth, such as this 10 foot by 100 foot length, from Johnny’s Selected Seeds.

Tough Tomato Skins Caused by Diseases

Certain diseases, such as Anthracnose and Curly Top Virus, can also cause tough skins on tomato fruit.

Anthracnose

Anthracnose is a fungus that causes the fruit on a tomato plant to rot.  Luckily, Anthracnose affects only the fruit – it does not affect the leaves, stems, or roots of the plant.

As a result, you can keep growing healthy tomatoes if you remove infected fruit.  You can either compost the fruit or feed it to your chickens after cutting away the fungus.

According to the Michigan State University Extension, fruit infected by Anthracnose has:

“tan, bubbled patches of leathery skin, both on green and red tomato fruit.”

https://www.canr.msu.edu/news/tomato_anthracnose_when_those_prized_ripe_tomatoes_go_bad

Anthracnose is more likely to affect damaged fruit, so avoid accidental cutting or bruising of your tomatoes when handling the plants or harvesting the fruit.  Anthracnose is not unique to tomato plants, and it can affect other garden vegetables as well.

According to the University of Massachusetts Amherst, Anthracnose does well in temperatures of 68 to 75 degrees Celsius, and extended periods of wet leaves and fruit.

To prevent Anthracnose, avoid watering plants from overhead.  Keep the fruit and leaves dry by watering at the base of the plant with a hose or drip irrigation system, rather than using a sprinkler.

ripe tomatoes on vine
Keep tomato fruit dry by watering from below to avoid Anthracnose, which affects only the fruit.

Curly Top Virus

Curly Top Virus is a disease that is transmitted by the beet leaf hopper.  Curly Top Virus affects the whole plant, and there is no known cure.

This disease will often cause the leaves to turn yellow and the plant to stop growing.  The fruit may also ripen prematurely and develop a bitter taste and tough, leathery skin.

According to the Utah State University Extension:

“Sugar beet is a common host and may serve as a virus reservoir.”

https://extension.usu.edu/pests/ipm/notes_ag/veg-curly-top-of-tomato

So, be careful if you are planting beets in the garden, especially near tomatoes.

Since there is no cure for Curly Top Virus, your best bet is to remove and destroy any infected plants to prevent beet leaf hoppers from spreading the virus. 

Tough Tomato Skins Due to Variety

Some tomato varieties have thicker skins than others.  For example, Roma tomatoes and San Marzano tomatoes (a type of plum tomato) are naturally thick-skinned.  As a result, they tend to resist cracking.

plum tomatoes
Plum tomatoes are one type of tomato with thick skin.

Sometimes, thick skin on tomatoes is by design.  Tomato growers who sell to supermarkets want thicker skins, since this improves a tomato’s ability to survive shipping in good shape.

If you want tomatoes with thinner skins, try some heirloom varieties.  According Johnny’s Selected Seeds, many heirloom tomatoes have thinner skin, at the expense of being more likely to split.

Cherokee Purple tomatoes are one heirloom variety with thin skin.  As with most thin-skinned tomato varieties, they are prone to cracking.  You can find Cherokee Purple tomato seeds on Johnny’s Selected Seeds.

Although heirloom varieties tend to have thinner skins, there are still some hybrid tomatoes with thin skin.

For example, Burpee’s Brandy Boy is an indeterminate hybrid tomato that has thin skin and a flavor similar to the familiar Brandywine tomato.  You can find Brandy Boy tomatoes on the Burpee website.

How Do You Soften The Skin On Tomatoes?

Sometimes, it is too late in the season to save some of the first tomatoes that ripened.  They already have thick skins, for one reason or another.

Is there any way to salvage them?  Here’s what to do with tomatoes with tough skins: skin them and cook them!

First, boil some water in a pot on the stove, and fill a container (or your sink) with cool water.

Next, when the water is boiling, toss the tomatoes in the pot and leave them in the water for 2 or 3 minutes.  (The water might temporarily stop boiling, which is ok – the heat will still loosen up the skins).

Then, take the tomatoes out of the pot put them in cool water (either in the sink or container).

Finally, when the tomatoes have cooled off enough, use a knife to peel them.  Cut out the stem part on top of the tomato, and peel the skin off.

Once you have peeled the skin off of your tomatoes, you can turn them into pasta sauce, pizza sauce, chili, or any other tomato-based dish.

You can also can your tomatoes, either with a pressure-canner or with a boiling water bath (you will need glass jars either way).  You can learn more about how to can tomatoes safely from the Old Farmer’s Almanac.

Conclusion

Now you have a better idea of why your tomatoes have tough skins and what you can do to prevent it.  You also have some ideas for what to do with tomatoes that have skins that are too thick to enjoy eating them raw.

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 Jon. Let's solve your gardening problems, spend more time growing, and get the best harvest every year!

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