Why Do Tomatoes Crack on the Vine?

Types

• Tomatoes can crack in two ways: concentrically and radially. Concentric cracks form in circles around the stem of the fruit, while radial cracks start at the stem and spread outward. Though different in appearance, concentric and radial cracks actually have the same cause.

Causes

• Cracking is caused by soil moisture fluctuations. In summer, as tomatoes reach the mature green stage of their development and the amount of water available to plants decreases, the fruit begins to ripen. When tomatoes ripen, the outer layer of their skin hardens to protect the fruit. If more water becomes available at this stage, it can cause tomatoes to swell, bursting their skin and creating cracks. This most often occurs in late summer when a long dry spell is ended by a heavy rain.

Solutions

• The best way to prevent cracking is to control the amount of water available to your tomatoes. While rainfall is obviously beyond anyone's control, you can apply a layer of organic mulch around the base of your plants, which serves as a buffer to prevent moisture fluctuation. Watering tomatoes regularly during dry weather will also lessen the impact of future heavy rainfalls. Tomatoes should be watered thoroughly once a week, especially while they are ripening.

Considerations

• While moisture fluctuations are usually the culprit behind tomatoes cracking on the vine, other factors may be at work. Severe pruning increases the likelihood of cracking. If you are growing tomatoes in a greenhouse, increased temperature and light levels, which can occur when you put new plastic on your greenhouse, can lead to cracking.