Question: We grew some wonderful cherry tomatoes this year, about a dozen varieties. The plants were fairly healthy, with just a few yellowing leaves, for most of the season. The trouble was that the tomatoes started splitting over the past few weeks. They were fine one day, and the next day we'd go out to pick them, and the ripe tomatoes would be cracked open. Not all the varieties cracked, but I started picking them before they were fully ripe thinking that might help. What causes this to happen, and how can we prevent it next year?
Answer: Tomato cracking is a common problem during seasons like the one we've just had. The tomato splits open, revealing the flesh and seeds inside and exposing the interior of the fruit to infection and rot. The cracks most often start at the stem end and extend down toward the base of the tomato. It's a problem that has several different causes.
First, certain tomato varieties are more prone to cracking than others. Cherries in general are more crack-prone than standard tomato varieties. The popular hybrid cherry tomato ‘Sungold' may have a delicious, sweet flavor, but it's notorious for having split fruits. The same goes for ‘Sweet Gold,' ‘Sweet 100' and several other popular cherry varieties. Do some research before selecting the varieties you plant next year; be on the lookout for selections with noted resistance to cracking. Some good choices include ‘Sun Sugar,' ‘Chocolate Sprinkles,' ‘Sweet Million' and ‘Gardener's Delight.'
Cracking also can occur in cherry and standard tomatoes when a prolonged period of dry weather is followed by heavy rainfall. This occurs because, when the plant is subjected to low moisture levels for an extended period of time, the skin of the fruit hardens, rather than growing. Then, when excessive amounts of water become available to the plant, the water is drawn up into the fruit where it collects and causes the skin to burst. To prevent this type of cracking, make sure your tomato plants stay well-watered during dry periods. Consistent moisture is the key.
Another cause of cracking in tomato fruits is excessive soil nitrogen, particularly when it's coupled with low soil potassium levels. Do not feed your tomatoes nitrogen-rich fertilizers because this promotes lush, green growth at the expense of quality fruit production.
Tomatoes also can split if they're left on the vine too long. Harvest the fruits regularly and store them at room temperature.
If cracking is problematic on standard tomatoes, the same issues are at play. Crack-resistant standard tomato varieties include ‘Marglobe,' ‘Jet Star,' ‘Cosmonaut Volkov' and ‘Early Girl.'
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