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Since some of us are getting more than our share of water this summer and others are get feast or famine, we're all lucky to be getting any tomatoes at all. During rough summers, every fruit counts. Cracking and splitting tomatoes are especially annoying, because they look perfect, up until they crack.

Why do tomatoes crack is a perennial question with a simple answer. Limited water followed by a lot of water will cause the inside of the tomato to swell up faster than the outside membrane of the tomato can grow or stretch, so it cracks. Preventing cracking isn't as easy as it first appears, since you can't control the rain. Here are a couple of tips to hedge your bets against tomato cracking.

Photo: Marie Iannotti


July 10, 2008 at 5:41 pm
(1) Nate says:

It’s a catch-22. If you overwater your tomato pants, the skin of the fruit will split. However, if you underwater or irregularly water them, then they will develop a physiological disorder known as “blossom end rot” or “BER” for short. This is where the plant cannot absorb and deliver the available calcium in the soil to the fruits.

Both splitting and BER allow for secondary pathogens to invade the inside of the fruit, causing it to decay.

July 10, 2008 at 5:43 pm
(2) Nate says:

“Tomato pants…”

Oh, man.

July 11, 2008 at 12:17 pm
(3) gardening says:

That would be so uncomfortable.

You’re right about the catch-22. But if tomatoes were easy to grow well, what fun would it be to brag about how good yours are?

July 11, 2008 at 5:08 pm
(4) mara says:

yes… Tomato pants!!!!

July 15, 2008 at 5:45 pm
(5) Sharon says:

I understand about the non/regular water supply causing certain conditions. But what if the leaves of the plants — actually just the edges of the leaves — turn white and start curling up. It hasn’t seemed to interfere with tomato production. Is it a problem we need to watch? It’s been in the 90s for weeks with occasional thunderstorms that dump bunches of water. We water them ourselves when we don’t get rain (city water vs. rainwater maybe?). Any comments or suggestions?

July 18, 2008 at 3:46 pm
(6) gardening says:

It could just be stress. Heat and humidity can curl leaves even if the plant is well watered.

Herbicide damage will curl leaves. If you sprayed anything nearby, it could possibly have drifted.

A worst case scenario would be tomato leaf curl virus. The virus is transmitted by white flies and, unfortunately, there’s no cure. I’d suggest taking a few leaves down to your cooperative extension for a definite answer.

May 16, 2009 at 8:17 pm
(7) P Gill says:

could a pesticide like cypermethrin cause tomato leaves to curl?

May 18, 2009 at 1:12 pm
(8) Marie Iannotti says:

P Gill, I’ve not heard of it causing curling. I think it’s more likely part of the damage caused by whatever insect your were spraying.

July 13, 2010 at 8:05 am
(9) craig dick says:

Splitting is caused by too much nitrogen with too much water. Blossom end rot is physiologicalb problem of not enough calcium. If it is new leaves that are curling then that is also a calcium deficiency. Reduce nitogen fertilizer and add gypsum or high calcium lime to the base of the plant.

October 3, 2011 at 4:11 pm
(10) Doug Tanaka says:

I’ve grown tomatoes for years and in my experience I don’t think it’s just a case of being over-under watered. For lack of space I grow mine in containers and keep them well-watered and fertilized and they grow just fine. The cracking does occur when the fruit is close to being ripe and we get a rain, but it also happens if we get a prolonged drizzle, not enough to affect soil saturation but enough to thoroughly wet the leaves. There’s a good chance they’d crack if watering was inconsistent but in my case that doesn’t appear to be the case.

My theory is that tomatoes crack when soil moisture is optimal and the surface of the leaves get totally wet and unable to dry out. In this case the roots, which we can think of as pumps, have access to ample water but because the surface of the leaves are wet the water in the vascular system has no place to go through normal transpiration. The water would normally exit the system through pores in the leaf surface but because those pores are now closed by a thin film of water the vascular system backs up, creating pressure, and it’s this pressure that causes the tomatoes to split. At least it seems to be the case with my own plants but I’d love to hear what others think.

As far as preventing them from cracking, if my theory is correct, a solution would be to cover the tomato plants when it rains to keep the leaves dry. This theory just now came to me and I haven’t had a chance to test it by covering one plant to see the results but I will report back if it does seem to make a difference.

October 3, 2011 at 4:30 pm
(11) gardening says:

Doug, that’s an interesting hypothesis. I hope you do give it a try and let us know if it makes a difference. I’d also like to hear what you come up with for covering them.

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