Why do my plums and cherries split after rain?
Splitting is a water problem with two halves — rain absorbed through the skin, and soil that swung from dry to wet — and only one of them is under your control.
- Difficulty
- beginner
- Time
- 20 min
- Read
- 3 min
Short answer
The skin stops expanding before the flesh does. Heavy rain on ripening fruit, especially after a dry spell, makes the flesh swell faster than the skin can stretch and it splits. Consistent soil moisture through mulching and watering prevents most of it; picking early in a wet spell saves the rest. Split fruit rots quickly, so use it at once.
Two separate mechanisms are at work. Roots take up water after rain and push it into fruit that is at its least elastic stage, close to ripe. And in cherries and plums, water sitting on the skin is absorbed directly through it. That second route is why cherries split within hours of a summer downpour even in soil that has stayed evenly moist, and why commercial cherry orchards are grown under rain covers.
Step by step
- Work out which fruit and which stage.Splitting almost always happens in the last week or two before ripeness, when the fruit has stopped expanding its skin but is still taking up water. Cherries split most, then plums and gages, then tomatoes and grapes.
- Keep the soil moisture even, all season.This is the controllable half. Mulch in spring over damp soil, water deeply in dry spells rather than letting the ground bake, and above all avoid the pattern of drought followed by a soaking.
- Pay particular attention to trees in pots and in grass.Both swing hardest between dry and wet. A potted cherry watered erratically will split almost every year.
- Pick early when heavy rain is forecast.Cherries and gages a day or two off ripeness will finish perfectly indoors. A downpour on ripe cherries can split most of a crop in an afternoon.
- Consider a rain cover for a trained cherry.A fan or a potted tree can be covered with a temporary polythene shelter or moved under cover for the final week. It is the only measure that addresses direct water uptake through the skin.
- Choose split-resistant varieties when planting.Cherry varieties differ substantially in splitting tendency, and nurseries state it. In a wet area it is worth choosing on that basis.
- Use split fruit immediately.A split is an open door for brown rot and wasps, and it will be rotten within a day or two. Pick it and cook, freeze or eat it straight away.
- Clear the split and rotting fruit from the tree.Otherwise it becomes a brown rot source and a wasp magnet, and the wasps then damage the sound fruit.
Tips
- Splitting is not a disease and no spray affects it. Anything that improves consistency of soil moisture is the treatment.
- Apples split much less often, and when they do it is usually a growth check — a dry period followed by heavy rain in late summer.
- Blackcurrants and gooseberries also split for the same reason, and mulching a soft fruit bed is the cheapest fix there is.
- A split at the stalk end tends to be growth-related; splits across the shoulder of a cherry are typically from surface water absorption.
Common mistakes
- Watering heavily to 'catch up' after a dry spell when fruit is ripening — The sudden availability of water is exactly what causes the split. Water regularly through the season instead, and go gently once fruit is close to ripe.
- Leaving split fruit on the tree — It rots within days and attracts wasps that then damage sound fruit. Pick it off and use or dispose of it.
- Assuming it is a disease and spraying — It is a physical problem with the skin. Nothing sprayed on it changes the water relations of the fruit.
Questions people ask
Why do cherries split when it rains?
Partly because roots take up water and the flesh swells faster than the skin can stretch, and partly because water sitting on the cherry skin is absorbed directly through it. Cherries are unusually prone to the second route.
Can I eat split fruit?
Yes, if it is picked immediately and has not started to rot. Splits let in brown rot within a day or two, so use it straight away rather than storing it.
How do I stop plums splitting?
Mulch and water consistently through the season so the soil never swings from bone dry to saturated, thin the crop, and pick a little early if a wet spell is forecast.
Do apples split too?
Sometimes, usually after a drought followed by heavy late-summer rain, and often around the eye or the stalk. The same consistent-moisture answer applies.