What is causing this damage to my tomatoes?

Splitting can be either radiate longitudionally or latitudionally. The splits going from stem towards the blossom end are the most common in my toms, when it occurs.
The cracking, or splitting of toms can have several causes:

**In my toms it's usually because the tom plant takes up too much water too quickly.

**The thing is, Daisy--it's all about the elasticity of the tom's skin. Different types of toms have more ot less elasticity naturally; however, other things can play a role here--for instance, if too leaves have been removed, the skin will become tougher and so the temp swings between daytime and nightime are too great for the skins to handle, so the rapid and dramatic expansion and contraction of the skin cells can result in cracking.
You get the picture here, right? Not enough leaves means rapid and high rise in temp from the sun, and when the sun goes down, the cooling can be quick as well. It is a time differential that is greater than it would have been had there been more leaves (or even shade) present.

**Irregular periods of slow and fast growth rate. This stresses the tomato's skin on a cellular level. Now, if the skin 'hardens' during the preceeding "slow-growth spell", and an ensuing period of "fast growth" comes along, then the skin can and often does split.

** Creating an overly succlent fruit by using too much of the inappropriate type of fertilizer/food. In other words creating a plant and fruit that has too much niotrogen and not enough potassium.

I see that I am beginning to border on the esoteric, I don't want to do that. If I think about this problem it really does just boil down to skin elacity and how certain conditions can challenge it and push it past the limits of it's retentitive capability.

Well, it isn't fair to make comments and not come with suggestions for dealing with the problem.

How one can deal with tomato spliting:

**Devise a proper watering program that avoids irregularity in times and amounts of water/food given.

**Do not prune your tom plants too heavily. You can prune and de-sucker your plants often, so long as you don't take too much at once. Once the plants have already produced 2-3 bunches (trusses) of toms keep suckering, but stop de-foliating the leaves.
At some point (depending upon where you live) you can see that flowers that are forming too late in the year will never make it to fall--cut the top of the plant off! You can remove these no-hopers too and then the plant can concentrate on putting it's energy into giving you nice and healthy fruits.

**Search and find a proper tomato fertilizer to feed your toms with keeping an eye on the "N" and "K" levels on the box. Avoid those fertilizers that contain too much nitrogen.

**Keep an eye out for pests and disease that can destroy your plants leaves. This is related to the second point above where I spoke of not pruning too hard.
It's a thin line between not having enough and having too much foliage. Finding this line is something that only comes with experience, and varies from county to county, state to state and country to country.

When I read back over this I seen that I have gone a bit OTT....no, not "a bit", a lot! I apologize. You didn't even ask for a comment. Embarassed

Now that I have formulated my thoughts on this, I am lothe to just delete them. Perhaps they will be helpful to someone.
These are my ideas, I can imagine that others may have different. Hopefully they will also add there thoughts as well and there will be a good choice for gardners to choose from.
I really must be more careful with posting comments.

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Sjoerd http://www.volkstuindersvereniginghoornenomstreken.nl/Page11.html

Oh gosh, I welcome your input and found your comments to be really helpful Sjoerd. I'm kind of getting into this tom thing. You know I have had one thing after another with my garden this year but I have learned a whole lot.

The problem in my case could be a couple things that you mentioned. I think water absorption is the biggest problem. Especially in the pots. Although they are large "enough" I suspect that down deeper in the pot, the soil is wetter than I realize because the soil on top feels dry. I think I wind up watering too much water too quickly -- I have to water the pots each day. I also wonder about the temperature situation. The pots are sitting on my driveway and they are shaded during the nice a.m./midday sun and then they get blasted with the intense, hot afternoon sun. Maybe they don't have time to adjust to the temp changes?

I only have two kinds of tomatoes, and def each type shows stress differently. The heirlooms have almost like stretchmarks going around the fruit. The other variety (whose name I can't remember at the moment) shows some spits at the stem area going down. They seem to split later in the ripening process so if I pick them just a little earlier, it's better.

Really interesting about topping and pruning the plants (which I didn't do with any organization!) and cutting them once it's too late in the season for them to ripen. I reckon around here, I have about another 6 weeks of hot sun but it doesn't frost until end of Oct or even early Nov.

OK, I'm rambling. How fun to jabber on about tomatoes though! Thanks so much, Gardengirl and Sjoerd!

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Daisybeans/MaryAnn

"Once the relation between poetry and the soil is well established in the mind, all growing things are endowed with more than material beauty." -Elizabeth Lawrence