Tomatoes cracking, which usually occurs on the upper part of the tomato can be either concentric (in concentric circles around the stem) or radial (radiating from the stem). The problem is often caused by pressure inside the fruit that is more than the skin can handle. Although a definitive reason for cracking is not known, one of the most common reasons is related to the tomato root system. Tomato roots are generally very dense and fibrous and quite efficient in picking up water. A problem is that the root system can get out of balance with the top of the plant. Early in the season it may be small in relation to the top growth. This can result in blossom-end rot during hot dry weather. As the season progresses, the root system may become so large and efficient that it provides too much water, particularly after a heavy rain or too much watering. The resulting large uptake of water is often the reason for the cracking tomato. To help eliminate cracking it is important to provide even, consistent watering. You can also use mulch which will moderate soil moisture levels. However, even if you do everything “by the book” there can still be issues with tomato cracking in some years. There is a great variation between tomato varieties as to their propensity to crack. Jet Star is an older variety which over the years has proven to be one of the most crack resistant.