More on the Importance of Early Thinning

It was too hot to sleep last night. So, I tried to wear out my brain with some studying and came across this article from UC Davis. The study was specifically for growing peaches in California, but the basic tenets regarding the reasons for early thinning, particularly when full bloom is followed by above average temperatures during the first month, would apply anywhere. I expect the the explanation for why the timing of thinning affects the final outcome of fruit size and quality would be highly likely to carry over to other tree fruits, as well.

The pros and those who have been growing fruit for many years are probably well aware of this information. But I know there are others here who, like me, have found it emotionally easier to thin a bit at a time. The understanding I gained from this article will make it easier for me to “just do it” all at once, instead of thinning gradually, a little more each day.


The problem with early thinning is that there is so much of it to do- and in home orchards the fruit may still be at jeopardy of being damaged by insects.

I didn’t read the article, I have already read many that show the advantage of thinning early. It is surprising that even raising the sugar of the fruit is mostly a product of “early” thinning.

What I don’t think has been researched is the difference between thinning, say, half way- to half the desired spacing at the “optimum time” and then coming back later to finish. Such thinning removes the vast majority of fruit in the tree and it’s easy to imagine that the small size of the fruit remaining isn’t enough to affect the size and sweetness of the fruit that makes the “final cut”.

That is not a research project likely to be undertaken anytime soon, but commercial apple growers use chemical thinners on the conservative side so as not to accidentally remove too much fruit. Final thinning is often done by hand well after that optimum thinning time. I’m guessing this is evidence that going half way and coming back later is probably just as good as doing it all at once.


That’s a good article MuddyMess.

For peaches, I think if you get most of the fruit off the shoots early, you’ll still get a good cell count on the individual peaches. The article doesn’t state this, but it’s known that a good part of the energy used to “feed” the peaches early on comes from stored carbohydrates in the wood and roots, whereas, after phase 1, the peach relies only on photosynthesis from the leaves. So as long as there is plenty of stored carbohydrates, leaving a little extra fruit on the shoots doesn’t bother anything IMO, especially for peaches which are pruned heavily, since they have a better root to top wood ratio. Just my theory based on observation.

I’ve noticed peaches which have most of the fruit removed from the shoot early, but are still slightly too heavy laden, are the same size as peaches on shoots which have only one peach on them at the end of phase 1. It’s the shoots which didn’t get thinned at all and have 10 fruit on a 1 foot shoot which have really small fruit at the end of phase one.

It’s was earlier this season I learned from a friend that cooler springs increase cell count of the fruit. I’d never heard that before. Your article provides the rationale for why that is the case. Thanks.

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Muddy, thanks for the post and link. I hope you got some sleep!

I underthinned my plums this year. My work schedule and health got in the way of my priorities😀. Apples and pears wont be a problem, and I did get the peaches thinned, but plums will be smaller as a result. I don’t know if that will affect flavor - Im hoping, not. Some branches that I could not even reach are now almost touching the ground!

So for next year - your article will come in handy as a reminder to get out there and thin!

And to make that job more accessible, after fruit have ripened, to summer - prune for size control. Somewhere between too tall for deer to reach, but short enough for me to thin properly. But that is Another topic.