Your oranges and lemons are splitting: it’s the watering, but not the way you think

You go out into the garden one September morning and there are four oranges split open on the tree and two more on the ground. Last week they were perfect.

The automatic conclusion is that the tree has been short of water, and the next thing almost everyone does is water more. That’s what will split the ones that are left.

The skin stopped growing before the filling did

A citrus fruit doesn’t grow like a balloon that inflates evenly. The rind forms in an early phase, and there comes a point when it stops growing: from then on it’s a shell, and a shell doesn’t stretch.

The flesh, on the other hand, keeps filling for months. As long as the water reaches it steadily, the difference doesn’t show and the fruit swells without any trouble.

The problem comes when the water supply suddenly jumps. The flesh absorbs fast, gains volume in days, and the rind can’t keep up. What gives is the part that can’t grow, and it almost always splits at the tip or at the base.

So the cause isn’t a lack of water. It’s the swing. A tree watered sparingly but steadily splits far less than one that goes from famine to feast.

Why here it happens in September and not in June

This is the local part, and it explains why the problem is bunched into a few weeks.

We’re coming out of four months without any useful rain. All that time the tree has been getting by on what the irrigation gave it, and the rind of the fruit has formed and hardened in lean conditions. It’s stiffer, with less give, than it would be in a year with the rain spread out.

And then the first storm arrives. Not a drizzle: a cloudburst that drops in two hours what falls in a month somewhere else. In a climate with rain spread through the year, the supply rises gradually and the fruit adapts. Here the jump is vertical.

There are two aggravating factors that are very much of this coast. The first is citrus in a pot or in a small tree pit, which is how a good share of the patio and terrace trees here are grown: with little soil around them, the change in moisture is even sharper than in open ground.

All the water that goes in and out of this tree passes through the clay you can see. The crown is three times wider than the pot, so any change (a storm, one watering too many) is felt in there long before it would be in a tree planted in the ground.

The second comes from the human calendar. In an area with so many holiday homes, September is also the month when the owner comes back and turns the irrigation up all at once after a summer on the minimum. The effect on the fruit is the same as the storm’s.

What to do once it’s happened

A split fruit doesn’t close up again. There’s nothing to put on it, and it’s worth saying so before anyone buys a product for it.

What you do need to do is take them off the tree, and soon. A crack in the rind is an open door: the fruit rots from there, draws flies and fungi, and a rotten fruit in the crown is a source of trouble for the healthy ones.

And yes, the question everyone asks: one that has only just split can be used. If you pick it the same day and it’s sound inside, you can eat it as it is. What you can’t use is one that has been open on the tree for days, even if it looks fine from the outside: all sorts have got in through the crack.

And keep an eye on what comes next, because the warning applies to the whole crop. If a few have split, the ones still intact are in the same situation: the same stiff rind and the same tree. The next few weeks decide how many more split.

And then, don’t do what your instinct tells you. Don’t water after a storm. The soil is soaked, the tree has more than enough, and adding water on top repeats exactly the jump that split the first ones.

How to prevent it next year

Everything that works points the same way: smoothing the curve, so the tree never feels the changes all at once.

Don’t switch the irrigation off all at once in autumn. It’s the most common mistake of these weeks: it has rained, so it gets turned off. What you should do is bring it down gradually, the same way it went up. How much water is really getting through, and how to check, is in how much to water the garden in summer.

Mulch. A layer of organic material over the tree pit is the most effective thing you can do for little money: it holds moisture, softens the peaks and makes a storm felt much less down there.

Look at the tree pit. If the tree has a ridiculously small opening surrounded by paving, every watering and every shower is an extreme. Making it bigger solves this and several other things.

And if it’s in a pot, think about the size. A citrus in a small pot will always live on a rollercoaster. Beyond a certain size, it either goes into the ground or gets a container with enough soil to cushion the changes.

One more thing: don’t mistake it for something else

If, as well as the splitting, you see the leaves turning yellow with the veins still green, that’s something else with a different fix: it’s chlorosis, which we cover in yellow leaves on a lemon tree. The two can happen together, because both have to do with how the water is managed, but they aren’t the same problem.

And if nobody has looked at the tree for years, the splitting is usually just the first thing you notice. In olive and fruit tree pruning we explain what gets checked on a garden fruit tree, and when.

In short

A split citrus isn’t asking for water: it’s telling you it got too much all at once after months of too little.

Take off the split fruit, don’t water after the storm, and for next year mulch and bring the irrigation down gradually instead of cutting it off. That’s all there is to it, and it works.