I tried to post this on the original topic and it has just gotten too long to scroll down to the current day. Congratulations on a great topic idea!
My tip is it takes 30 well-lit leaves to create a perfect piece of good sized fruit- and often a crop the following season. This is much more important than distance between fruit. First consider the meaning of well lit, which is a leaf that has uninterrupted sun throughout the day. It is more than a matter of thinning fruit but also thinning branches and mopping out garbage growth casting unnecessary shade when you come to thin fruit. Shaded leaves permanently lose their ability to photosynthesize- at least with apples, but probably most species- so shade should be controlled even in the spring if you have the time.
For fruit with spurs, the most important leaves serving fruit are the spur leaves themselves, with the next closest leaves being the second ,most important. The latter are what to consider with peaches,plums and other fruit not spur-centric. Plums, cherries and all smaller fruit need a ratio of leaves relative to their smaller size, I suppose and practice- let’s say 10-15 leaves per fruit for good sized plums. But E. plums are capable of creating relatively high brix, so I wonder if this doesn’t require relatively more leaves- but maybe I’m over complicating the issue. Why stop there, there’s also the question of the size of the leaves! Keep swimming, there’s bound to be terrafirma nearby.
I’ll do some more heavy pruning taking that into account. A single tree heavily pruned with good leaf count on one side only would be a good experiment.
I do notice large fruit size and good quality don’t always happen at the same time. Costco often has very large beautiful fruit but sometimes the quality is not good.
My thinning is always predicated on leaf to fruit ratio. But I’m not counting anything. It’s just the computer in my head asking is this enough foliage for the amount of fruit I’m leaving? I had one instance this yr of under thinning to help calibrate things. And have more fruit on some trees than usual. That will help further.
Another factor of proven importance is date of fruit maturity. Varieties that mature late in the yr can often carry a heavier fruit load than early varieties. That’s a pretty easy to understand concept. So I’m leaving a heavier than normal crop load on some pluots that don’t mature until the August to Oct time frame. That’s 6-7 months hang time on the tree compared to 3 months for the early variety that I underthinned this yr.
Yes, it’s mostly a concept to carry in your head while you strip off thousands of surplus fruit. I certainly don’t do any counting as I go. Fruit needs to be falling like rain when you are dealing with full sized trees. Of course, with my favorite varieties I will slow down- no down-pour when I thin nectarines.