It’s December, my oranges aren’t sweet yet, but they’re splitting. Oh no!

Happens every fall, actually. Just as the cool nights start to turn the rinds from green to orange, and just as the first rains arrive, navel oranges begin to split.

My orange tree whose fruit is splitting is a Cara Cara navel orange. I’m told that blood oranges and Valencia oranges also split sometimes but I’ve never seen that. I also read that some mandarins get split rinds, but out of the hundreds of mandarins of different varieties that I have on my trees I’ve found only two with split rinds. This phenomenon is a navel orange problem mostly.

Split usually starts at navel

Usually the cracking begins at the navel, the bottom of the orange, which seems to be because that navel is a weak point in the rind. It’s like a natural scratch in the rind that is the first spot to tear open under pressure.

Split starting at navel.

What causes the splitting?

You’ll find some claiming to know the causes in detail. For example, one piece of research from South Africa talks of the contributions of factors such as nutrient imbalances, warm and humid climatic conditions, irregular irrigation, and heavy crop loads.

And commonly, there is a story told about the splitting of navel oranges. It goes like this: In California, the early fall weather is warm and dry. During such weather an orange tree might pull water from its fruit if it is in need of moisture. Then the glorious rains of late fall arrive. At that point, the dehydrated fruit take in more water than their skin can handle and . . . split!

One University of California Cooperative Extension farm advisor told me that he has observed that most of the trees with a lot of oranges and mandarins splitting after the first rain in fall were not watered enough before the rain — during summer and early fall.

It all sounds plausible.

Yet elsewhere there is no claim to understand exactly why oranges split. The California Master Gardener Handbook, published by the University of California, summarizes the symptom of split navel oranges this way: “Cause unknown.”

How to prevent the splits

When there is a claim to know the cause of splitting, it is often accompanied by advice as to how to reduce it. The most common advice is as follows: “The best remedy is to irrigate evenly.” A less common piece of advice is to mulch and fertilize trees appropriately.

Yet there is never any evidence given that these practices significantly and consistently reduce splitting, not to mention that the advice itself is usually so unspecific as to be hard to follow. (How exactly does one “irrigate evenly?”)

What makes sense to me is that one should water an orange tree during warm and dry times, especially during stressful Santa Ana events. If you don’t, you can see the tree cup its leaves to display its stress. So of course, water your tree enough and everything about the tree will be healthier, including the integrity of its fruit.

Beyond this basic watering, I land on the conclusion that navel oranges are still going to split to a degree. In other words, it’s still partly out of our hands, it’s also related to weather and internal tree mechanisms that we cannot or don’t know how to manipulate effectively. At least, with good watering practices, the proportion of split fruit remains small.

What to do with split oranges?

So here I am with a little Cara Cara tree carrying about 50 oranges and six of them have split this year. That’s a higher proportion than past years, but it still leaves me with about 44 good oranges. Not a big problem. 

Split Cara Cara navel oranges removed from tree.

What to do with the splits? Left on the tree, they eventually gather mold and rot. You might as well pull them off before the rot gets bad. The problem is that they aren’t sweet yet so you don’t want to eat them. It’s still too early to pick navel oranges when they split here in late fall. 

Or is it? Might as well taste.

She likes it?

Surprisingly, the split oranges were mostly worth eating. I wouldn’t call them good, but not one went straight to the compost bin after all.

You might also like to read my post:

When to pick oranges and tangerines

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