How to thin a peach tree?

Aside from mulching around the base (which I wrote about in a different post, and accomplished thank you very much) I've also heard that my peach tree(s) might do better by being thinned. Great, I've got a pruner and a small saw and a ladder if I need it, so I'm all ready to go...but what exactly should I do?

How do I know which branches to cut? Am I looking to only eliminate small branches with no peaches on them, or major branches with peaches and all? What's the strategy here?

And, what is the best time to do this? Right now my tree is full of peaches that are just starting to become ripe. (Plucked and ate one yesterday that was like 60% of the way there.) Should I wait until after the peaches are gone? Should I wait until next spring?

(I'm sure there are countless articles and videos on this, but I prefer to ask a forum for various reasons previously stated elsewhere on this site, etc etc.)

i may be mistaken, as it's been decades since i've been in peach territory, but i think when they say thin they mean thin out the fruit (or flowers).
it was my first job as a preteen out in the country to go out and thin out the peaches when they were small, like almond size. I was told something like, almost a palm's breadth between. again, this was a long time ago, so hopefully someone else will chime in. This helps the fruit grow better and larger.

yup, my understanding of peach thinning is similar, thinning out young fruit (usually younger than it sounds like you’re at) to improve airflow and to have fewer fruits that get bigger than they would otherwise.

Ahh, gotcha. So really I was writing about pruning, not thinning. (Should I be pruning too?)

As far as thinning goes, I mentioned in that other thread that a lot of the fruits on this tree, back when they were almond-sized, fell off on their own. Are you saying I should have knocked off even more?

There are two schools of thought on pruning trees:

Never prune technique of holzer and fukuoka:

https://permies.com/t/2590/prune-technique-holzer-fukuoka

Traditional fruit tree pruning:

https://permies.com/t/2608/woodland/traditional-fruit-tree-pruning

Here is a helpful thread on how to prune:

https://permies.com/t/106899/prune

Thinning fruit not only allows/encourages the remaining fruit to get larger, it protects branches from breaking from the weight.

I have read that summer pruning is less likely to simply encourage the plant to go crazy, which pruning at the wrong time of year can happen.

If the tree is wild and has never been pruned, I have read that just leaving it be is a healthy choice, unless there is a branch that's damaged.

Pruning has a lot of subtleties, so I would do some reading... and more reading... there are many different opinions on the subject!

How old is your tree? Usually it's not recommend to prune before the tree starts bearing or only limited to establishing the scaffolds. Next several years when the tree is in prime production, only thinning out weak and crossing branches is needed. When the tree ages, since peach only bears on 2nd year wood and those are moving far out or high up the canopy over time, some people would prune to rejuvenate new growths. One people I know swears by it and took out a third of his 10 year old peach tree and got bountiful fruits later.

As with most things, it depends. When pruning fruit trees, I'm usually responding to the amount of growth over the past season, and taking into account some idealised "future tree" that I want. A healthy peach tree in its prime years can put on a lot of growth. This ends up crowding the interior of the crown, which responds by dying back and creating a hollowed out shape, with the future productivity of the tree concentrated out at the perimeter.

In a natural setting, a likely outcome to unchecked growth is that long branch extensions lead to breakage, usually from a combination of weight and leverage and exacerbated by wind. The highest risk for this is when the fruit is maturing and if there's a lot of it on the tree, so if you're doing the no prune thing, then thinning fruit is important if you don't want your tree to get ripped up. You'll also get bigger fruit if there are fewer of them competing for resources.

A large limb breaking off the tree can be anything from a setback to a terminal event. The wound could damage the tree badly enough that it starts to die. Or, it could just open up a section of the crown to emergent shoots and reinvigorate the tree. A lot depends on the health and type of tree...some species are better at renewal than others, and in our climate peaches are among the worst. Apples, pears, some plums, persimmons, and feijoas are just about indestructible at our place. Peaches, on the other hand, I plan on replacing within 5-7 years because that's about all I get out of the average tree before it succumbs to one malaise or another.

When they're young and vigorous, I tend to remove about 1/3 of the previous season's growth with each pruning to open up the structure and reduce the length of leaders. That helps keep them compact and avoid crowding, and also means I don't need to thin as much fruit in the summer.