Thinning fruit and biennial bearing- all of it

I haven’t quite finished thinning peaches yet in my own orchard but have been doing it in other orchards since finishing the second of two insecticide sprays we use to protect the orchards we manage. My orchard is the only one that gets the luxury of early apple thinning- I try to do it within a week or two of petal fall of latest blooming apples. We don’t use chemical thinners for apples.

Those of you in warmer climates may already be long since done thinning but I now have a little time to write on the subject as some of you probably do also, so I’m beginning the discussion with my own thoughts based on my experience in many orchards around southern NY (where we can get a lot of rain throughout the growing and harvest season).

First of all, I’ve come to the conclusion that most of the sweetening benefits from thinning peaches occurs whether you thin earlier or later, as long as its done 2-3 weeks before fruit ripens. It may be true of most species. I admit that I haven’t gone to the effort to test my theory in a research based manner, but anecdotally it has become quite clear that is the window for getting sweet fruit when it comes to cloudy, cool weather. If it is sunny and warm in the 2-3 weeks preceding harvest of most fruits, they will get up their sugar, when cool wet weather precedes, you can thin all you want and peaches, at least, will be worthless (people in humid climates need to know this when they are evaluating varieties for relative good flavor). I think this applies to apples and most other fruits as well, but it’s difficult to evaluate how much water and how much warm sun in involved in the equation in my climate. People in areas with reliable sun can gauge the affect of too much water only- at least in a research based way.

So even if you are tardy and didn’t have time to thin fruit early, don’t be discouraged from thinning if you still have at least 2 weeks before harvest of fruit on that tree. Leaves put most of the sugar into fruit in that very narrow window, in my opinion- much of the sizing up occurs also.

I’ve always tried to thin my own peaches extremely early because the literature suggests that in the early part of fruit development fruit expansion occurs by cell division while later fruit size comes as the result of larger individual cells- more cells, rather than bigger ones is supposed to especially benefit the quality of fruit, but I just don’t believe that anymore. I’m not sure if the assumption was a creative leap or not, because research on the subject is scant and the primary interest of funded research has never been to help growers achieve higher brix fruit so much as getting more bins per acre- and good storage qualities (relatively more cells in ratio to volume may help for that).

Fortunately, some breeders are now starting to look at higher sugar as a virtue, but unfortunately also looking at lower acid the same way- at least with peaches and nects. I want high sugar and high acid with all of my peaches and nects- or most of them, at least. My palate was never watered down by a high indulgence in foods and drinks laced with high amounts of corn sugars so low acid fruit can seem insipid to me.

On a final note, and with a thanks to Olpea for bringing it to my attention, in humid climates, don’t rush to finish up thinning saucer peaches. Hold off so you can focus on the cracked ones as they are almost certain to rot before they ripen. Leave at least twice as much fruit as you plan to harvest in the first go through.

I happen to consider TangO’s an exceptionally good peach, as do most of my customers- the 2% points of higher sugar it achieves over most other peaches is a big part of it, I’m sure- but like Honey Crisp in the apple realm, it can be very difficult to grow- for TangO’s, because rain during the growing season tends to make a mess of it.

My well thinned TangO’s are twice the size and better quality than what I’ve seen at any farm market or store, so my hunch is that most growers can’t be bothered to thin the variety adequately- it is very time consuming to do it right.

I should also mention that I remove clusters of flowers from Goldrush, and if it wasn’t that a Jonathon right next to my two Goldrush trees also has crop, I would probably credit that for having fruit on it this season.


My nectarines aren’t fruiting this year - the one I should have thinned heavily last year but did not, and the one that only bore lightly.

In my region, all but most favorable sites lost entire nect crop. In a few there is seriously freeze damaged fruit. All this occured very late March when buds were only swollen and the only green showing was on J. plums and cots. The only plums I have this year are from a couple varieties of J. plums. In the region, nects were, by far, the most vulnerable fruit to this very early spring freeze- whether bred in CA or NJ.

Flowers were all fine, embryos were killed. A degree or two warmer and all would have been fine. One night.

Gamblers have to embrace the risk as part of the thrill and regard regret as the emotion that makes later success so much sweeter. Well… that’s more or less what I suggest to my customers.

Honestly, if they got a great harvest every year, they wouldn’t appreciate it as much.

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Mine didn’t flower, so I was thinking it was a thinning/biennial problem


My Red Havens had approx 500 peaches per tree last year, heavy load. Most were perfect, sweat and good sized except the lowest to the ground. I observed much less new fruit wood and much lower blossoms this year. Now, there could be other factors I have not considered. I left to many downward facing fruit wood and they currently have smaller fruits

This year with a lower fruit set, there is an excess of new fruiting wood. I will need to thin the fruit wood next Spring, I assume. Glad to do fruit wood thinning vs. feeling like leaving odd placed fruit wood just to get the volume.

One other observation I have. I have read many times, each peach needs xx number of leaves to make a good fruit. I have seen many really nice peaches on nearly leafless branches when the peach is close to fork of a healthy branch.

What may not be known is how far the leaf can be away from it and still provide sugar for the fruit. some carbos go up to serve growth some go down to serve fruit, I guess, but when growth gets too far away from fruit sweetness suffers and fruit in more shaded parts of trees almost always tend to be less sweet.

I should have mentioned that I constantly prune as I thin fruit in vigorous trees, and especially peach trees. New wood or old wood where fruit didn’t set is often removed to allow both fruit and the new wood I want to get better light and air.

I believe this is why I manage so many peach trees over 20 years old that are still very productive and vigorous. Most peach trees I mange get a late spring prune and another in mid-summer. Trees on my property are pruned continuously as I walk through my orchard. I’ve got to go out right now and work on peach trees in my nursery- they are growing so fast and I want them to spread out and not grow straight up.

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