Irregular watering and fluctuating temperatures.

It has been a very difficult year for tomatoes mine must be about six weeks behind what they were last year and have only just starting to ripen have had to shut the greenhouse some nights because of the temperatures being so low when I would normally leave it open.

Thank you for your answers to my tomato question

splitting usually means irregular watering as already said, getting too dry and then soaked etc. I have been extra careful about that this year and have had no splitting at all. I grow all kinds of tomatoes outdoors, and even with a poor Summer they have done well, in fact we have a glut of ripe tomatoes at the moment. The bright yellow cherry tumblers have been wonderful, so sweet.

Irregular watering happens when the pot has been allowed to dry out and growth stops for a short time. Then when more water is given the tomatoes begin to swell again but the skin has set so it breaks to make room for the swelling fruit inside. Sometimes it happens in a ring like yours and sometimes you get a split down one side. You can still eat the tomatoes.