Cracked tomatoes? What's behind it and how to prevent it
Weeks of heat, then a heavy thunderstorm – and suddenly your best tomatoes split open. Here's what's going on and how to protect your harvest.
Late July is when many tomato plants finally hit their stride – and that’s exactly when it happens: fine cracks around the stem or long splits down the side. It’s not a pest and not a disease, but almost always a matter of water supply. The good news: a few simple habits will get the problem under control for good.
Why tomatoes crack in the first place
A tomato cracks when its inside grows faster than its skin. After a dry spell, the plant suddenly pulls in large amounts of water – say, after a summer thunderstorm or a generous watering – and pushes it into the fruit. The flesh expands quickly, the skin can’t keep up and tears. Nearly ripe fruit is especially vulnerable because its skin is already thinner and less elastic. Variety matters too: thin-skinned cocktail and beefsteak tomatoes split more readily than sturdy salad varieties.
Rain after heat: the critical 48 hours
The classic cracking scenario in July and August: two weeks of heat, then a thunderstorm rolls through. If your tomatoes are growing outdoors without cover, it pays to check the forecast. If heavy rain is on the way, pick every fruit that has started to change colour – shifting from green towards orange or red. They’ll ripen perfectly well on the windowsill and escape the split. The risk stays elevated for a day or two after the rain, too, as the plant keeps taking up water.
Water evenly, not abundantly
The biggest lever against cracking is a steady water supply. Instead of a small splash every day, water deeply every two to three days – ideally in the morning and directly at the root zone, not over the leaves. That way the fruit grows at a calm pace and the skin can keep up. After a run of hot days, resist the urge to catch up with one huge watering; spread it out over several days instead. Potted tomatoes naturally need water more often – the key there is that the soil never dries out completely.
Mulch and rain cover: quiet insurance
A five-to-ten-centimetre mulch layer of grass clippings or straw acts as a buffer: it keeps soil moisture even and smooths out the swings between watering rounds and downpours. If you also grow your tomatoes under a simple roof or shelter, you decouple them from rain entirely – which, as a bonus, protects against late blight, a disease that loves wet foliage. A spot against a house wall under an overhanging roof often does the trick.
Cracked fruit: eat it or toss it?
A freshly split tomato is no case for the compost bin. Pick it promptly and eat it the same day or the next – the flavour is completely unaffected. Only if mould is already showing in the crack, the fruit smells fermented or fruit flies have moved in should it be discarded. Cracked fruit isn’t suitable for storing, though, as the open wound is a gateway for fungi and bacteria. Tip: a batch of split tomatoes makes an excellent quick sauce.
Keeping on top of it
The pattern behind cracked tomatoes is almost always the same: irregular water. Once you set up a solid watering routine, the problem rarely comes back. In Rootivo, the Care tab helps you do exactly that: the weather card shows you rain ahead of time, and the daily watering tasks keep you on a steady rhythm – so your tomato harvest gets through high summer without a single split.
Im Lexikon: Tomate