Preventing Cracking in Heirloom Tomatoes

It is so disappointing to carefully tend to your heirloom tomato plants, waiting for the delicious reward of perfect juicy tomatoes, only to see them crack and split on the vine. Because heirloom tomatoes have thin skins, you tend to see more splitting and cracking, especially with inconsistent watering. Here are a few tips that may help you to decrease or prevent cracking of these delicious tomatoes.

If you’re anything like me, the expectation of that first flush of vine-ripened heirloom tomatoes is a that “old-fashioned taste“ that you just can’t get out of thick-skinned grocery store tomatoes that have been bred for shipping and shelf life rather than taste.

It can feel devastating to anticipate a bountiful harvest, only to see heavy amounts of cracking and splitting in the skin! 

Sometimes the cracking will just mean a shorter time on the counter before you eat it, but deeper cracking can also allow disease to enter the tomatoes and result in total loss.

Cracking can occur at all stages of fruit growth, but as fruit mature they become more susceptible, especially as color develops. 

Some varieties of tomatoes are more susceptible to cracking than others, regardless of whether it is an heirloom variety or a hybrid variety.  For information on heirloom varieties that are less prone to cracking, see the heirloom variety charts.

Two Main Types of Cracking

There are two different forms of cracking in tomatoes, one of which is primarily cosmetic and one which is a result of weather and growing conditions.

Concentric Cracking:

Concentric cracking occurs in a ring or rings around the stem end.  This is a genetic characteristic and can’t really be prevented. 

The good news is that there is absolutely nothing wrong with the fruit, and the taste is fine.  Scar tissue forms over the cracks, preventing access to bacteria and fungi, which would result in rotting. 

Occasionally, with heavy rains the scar tissue may open up resulting in some rotting.  This is different than the cosmetic cracking and you will want to harvest those tomatoes and cut off the portion with open cracking.

If the cosmetic look of “non-open” concentric cracking bothers you, and you grow your own tomatoes, select varieties that the seed catalogs refer to as “smooth” or “perfect”.  Sometimes they will note whether the variety is “resistant to cracking” also.

Longitudinal Cracking:

Any tomato variety can develop longitudinal cracking, where the tomato splits from top to bottom.  Longitudinal cracking (also referred to as radial cracking) starts at the stem end and progresses toward the blossom end. 

This type of cracking happens when the internal expansion in the tomato is faster than the expansion of the “epidermis”, forcing the skin to crack to accomodate the expansion. 

Essentially the skin on a more mature tomato can’t expand anymore in response to the absorption of water, so the skin splits open. 

Don’t be afraid to eat these split tomatoes, or use in cooking, as long as you harvest them before bacteria and fungi contaminate the split.

Cracking can occur at all stages of fruit growth, but as fruit mature they become more susceptible, especially as color develops.

Preventing Cracking in Heirloom Tomatoes

With respect to concentric cracking, the only thing you can do is select varieties that do not exhibit this genetic characteristic.  That means reading the seed catalogs carefully and looking for phrases such as “smooth tomatoes”, ”perfect tomatoes” or “resistant to cracking”.

For radial cracking, prevention is achieved by:

1. reducing fluctuations in soil moisture, especially during later stages of development. Make sure you don’t let the plants dry out and then deluge them with water. Keep the watering nice and consistent. A good rule of thumb is to poke your finger in the soil and when it is dry down to 1 inch, it’s time to water.
2. selecting crack-resistant varieties;
3. maintaining a good foliage cover, since exposed fruit are more susceptible;
4. harvesting your tomatoes at an earlier stage of development (of course, this results in less of the sugars and complexity of flavors developing).

Do you have any photos of cracked tomatoes that you would care to share to illustrate the point?  I’d love to share them if you do!

More on Heirloom Tomato Varieties

How to get the earliest tomatoes

Which heirloom tomatoes have the most flavor

Best heirloom tomato varieties trialed in 2020

Growing tomatoes in pots

Try this smoked tomato jam for a Winter treat

Happy Trails….and may your harvest be crack-free!