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Preventing Cracking in Heirloom Tomatoes

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. You tend to see more splitting and cracking of heirloom tomatoes over hybrid tomatoes due to the thin skin of most heirloom tomatoes.

There are ways of preventing, or at least decreasing, cracking in heirloom tomatoes. Here are a few tips that may help you to success.

Baskets of heirloom tomatoes at the farmers market
Baskets of heirloom tomatoes at the farmers market

The time for baskets of beautiful, flavorful heirloom tomatoes is drawing near.   If you’re anything like me, you’ve been watching and waiting impatiently for that first flush of vine-ripened heirlooms, anticipating the taste of that sun-warmed globe of fresh goodness. 

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:

Examples of concentric cracking in heirloom tomatoes
Examples of concentric cracking in heirloom tomatoes

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 and allow access to disease.  If the cosmetic look of 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:

Example of longitudinal cracking in heirloom tomatoes
Example of longitudinal cracking in heirloom tomatoes

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

Array of heirloom tomatoes with no cracking
Array of heirloom tomatoes with no cracking

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!

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

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Kelly Chapman sr

Friday 5th of August 2016

My cracking occurred in circles around the top of the tomatoes. What kind of cracking is this and is it safe to eat?

Pattie Dawson

Saturday 10th of August 2013

Unfortunately I have many examples of tomatoes cracking. If you would like a picture I can e-mail one. Just send the address.

Dorothy Stainbrook

Monday 12th of August 2013

Hi Pattie, I'm so sorry about your cracking problems. Some tomatoes are more prone to it than others, and knowing what the perfect watering regime is doesn't necessarily mean it's easy to pull off. I had some cracking problems early on this year so (unfortunately) I got some pretty informative photos. Thank you for the offer though. Good luck with the rest of the season!

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