Tomato Rescue: What Causes Tomatoes to Crack?

There’s nothing like the anticipation of waiting for a tomato to ripen. You can almost taste it every time you look at it. And there’s nothing like the disappointment of seeing cracks around the top and splits down the side. What can you do to prevent this kind of damage to your tomato harvest? We’ll explain why this happens and share our tips for preventing tomatoes from splitting and cracking.

The quick answer is that tomatoes split because they grow faster than their skin can keep up. Oops! Now they’re a little too big for their britches!

Tomatoes crack because they absorb water faster than their skin can stretch. This most often happens when heavy rain follows a dry spell or after a tomato plant is watered deeply after becoming too dry. Tomatoes are especially susceptible once they begin to ripen. Consistent watering, mulch, and harvesting fruit at the breaker stage before storms can greatly reduce cracking.

It’s pretty common here in the Midwest and other growing zones to have a period of hot weather followed by heavy downpours. This often results in split tomatoes.

As the tomatoes grow, the flesh and the outer skin normally grow together. With consistent soil moisture, the fruit expands gradually, and the skin keeps pace with the growing flesh. However, if there’s a dry spell followed by heavy rain or deep watering, the plant will take up the moisture too quickly. As the flesh expands, the skin can’t stretch quickly enough to keep up, causing the tomato to crack. 

Green tomatoes are less likely to crack because they are still firm and their tissues are better able to accommodate growth. As tomatoes ripen, the flesh softens while the fruit continues to expand. At this stage, if the plant suddenly absorbs a large amount of water, the fruit can expand faster than the skin can stretch. 

This is why tomatoes are more likely to split after they’ve started turning color, especially after those impressive summer thunderstorms. Fully ripe tomatoes are especially vulnerable. Harvesting tomatoes at the breaker stage, or once they have developed most of their color, can help prevent losses.

While heavy rain is the most common trigger, cracking is usually caused by a combination of factors. These include inconsistent soil moisture, the stage of ripeness, and the natural characteristics of the tomato variety. 

Genetics play a role in how susceptible a tomato is to cracking. Some varieties naturally have more elastic skins that are better able to accommodate rapid fruit expansion, while others split more easily after heavy rain or inconsistent watering. Large beefsteak and many heirloom tomatoes tend to crack more often than smaller paste tomatoes, although there are plenty of heirloom exceptions. 

Radial

Radial cracks begin near the stem and run down the sides of the tomato. These are often deep cracks caused by rapid fruit expansion after a heavy rain or inconsistent watering. 

Concentric

Concentric cracks form as circles around the stem. They’re often shallower than radial cracks and may appear as the fruit reaches full ripeness. Some tomato varieties are naturally more prone to concentric cracking than others. 

Consistent watering is the best way to prevent tomatoes from cracking. Avoid letting the soil become extremely dry before soaking it again. Large swings in soil moisture cause tomatoes to absorb water rapidly, increasing the chance that the fruit will split. 

We like using drip irrigation because it delivers water slowly and evenly, helping maintain consistent soil moisture throughout the growing season.

To keep soil moisture consistent, water deeply whenever the top inch or two of soil begins to dry rather than watering lightly every day.

If tomato cracking is a persistent problem in your garden, selecting varieties that are naturally resistant to splitting can make a noticeable difference. While no tomato is completely crack-proof, some varieties have been naturally selected over time to withstand fluctuations in soil moisture better. 

If you’re selecting seeds for growing next season, consider growing varieties that are naturally less prone to cracking. 

Some of our favorite Sow Right Seeds heirloom tomatoes are:

Roma - A classic paste tomato with a firm flesh that is less prone to cracking.

Striped Paste - An heirloom paste tomato with thick walls and heavy yields.

Rutgers - A dependable slicing tomato known for its disease resistance and relatively crack-resistant fruit.

Homestead - A heat-tolerant heirloom that also resists cracking better than many large beefsteak varieties. 

Marglobe - A productive determinate heirloom perfect for slicing and canning.

Jubilee - A beautiful golden-orange heirloom with a mild flavor. 

One of the easiest ways to prevent cracking is to harvest tomatoes before a major rainstorm. Once tomatoes reach the breaker stage–when the first blush of color appears–they’ll continue ripening indoors without a noticeable difference in flavor. 

I’ve learned this lesson the hard way. After a heavy rain, I’ve noticed an increase in cracked tomatoes, especially with my cherry tomatoes that were ready to be picked. It is frustrating. So pay attention to the forecast. 

If your tomatoes are at the breaker stage and heavy rains are coming, go ahead and harvest to avoid cracking. Let them finish ripening indoors. 

What if you check your garden after a rainstorm and see that several of your tomatoes have already split? Don’t worry. You probably don’t have to throw them away. As long as the cracks are fresh and the tomatoes haven’t begun to rot, they are usually safe to eat.

When this happens to me, I go ahead and pick them to use right away. If they’re left on the vine, the cracks become entry points for insects and mold. Once I’ve cut out the split portion, I eat them, freeze them, or cook them. 

A crack exposes the inside of the tomato to bacteria, fungi, insects, and moisture, so that the fruit won't keep nearly as long as an undamaged tomato. 

You’ll want to throw them out if they are:

• Soft and mushy around the split

• Mold growing inside the crack

• Has a sour or unpleasant smell

• Signs of insects inside

• Decay that extends beyond the cracked area

Put inedible tomatoes in your compost bin and turn them into garden soil.

Tomato cracking and catfacing are often confused, but they're different problems. Cracking appears after the fruit has developed and usually happens when tomatoes absorb water too quickly after a dry spell. Catfacing occurs much earlier, during flower development and pollination, resulting in deeply scarred, misshapen fruit. While catfaced tomatoes may not be as attractive, they're usually still safe to eat once damaged areas are trimmed away.

Tomato cracking is one of the most common (and frustrating) problems gardeners face, especially after heavy summer rains. While you can't control the weather, you can greatly reduce cracking by watering consistently, mulching to maintain even soil moisture, choosing crack-resistant varieties, and harvesting tomatoes at the breaker stage before storms. If a tomato does split, harvest it promptly and enjoy it while it's still fresh.