Some of you have probably noticed that I’m obsessing on fruit sweetness this year. I’d like to begin a discussion on what can be done beyond deficit irrigation to bring up brix.
Lately I’ve been thinking about fruit thinning. Advice on the subject usually emphasizes the importance of early thinning- including mine. Now I’m having some second thoughts. Yes, early thinning improves the chances of annual bearing for apples and pears, at least. It also increases the size of fruit by increasing the number of cells instead of the size of existing cells as later thinning does, which should help make sweeter fruit.
However, I now wonder about the affect of thinning about 3 weeks or less before the harvest of stone fruit. It is during those last 2 to 3 weeks that the sweetness of the fruit is mostly determined, based on the weathers influence. If there are lots of gray and/or rainy days at that time leading up to harvest brix will be down.
If that affects sugar negatively, why wouldn’t late thinning of overladen trees have the opposite affect? The same number of leaves would be serving fewer fruit and they are responsible for the production of most of the fruit’s sugar.
I did some quite late thinning at one orchard I managed this season, just 2-3 weeks before the harvest of Red Havens, and they are the sweetest peaches I’ve ever taken from those trees, topping 15% sugar on a year with quite a bit of rain (though the weather was pretty good leading up to harvest).
Next year I will do a more controlled experiment on different branches of the same tree.
Of course, however, the Redhavens I’m talking about still reached good size. I’m harvesting some huge Coral Star right now and who needs a peach that weighs a pound? Half way through and I’m full. Huge can be great for culinary purposes though.
If you are shooting for 2-3 points increase then the last 2-3 weeks is a likely time frame. But to reach a big increase like 10 points it’s more like 2-3 months. My experience says 10 points is possible, East coast 15 and west coast 25 brix nectarines.
I can tell on certain fruits if it’s going to be really high brix more than 2-3 weeks before harvest. It has a dark speckled appearance. I should have taken a picture of my Honey Diva a month before harvest and half of full diameter. They shouted high brix.
Even here in the North East, when we had 2-3 dry weeks prior to harvest, I measured nectarine brix in the 20-27 range, I liked them best in the 22-25 range, below 17-18 doesn’t cut it for me, and that’s why I don’t grow any peaches. Here is how I rate my nectarines:
<17 not worth eating
17-18 good
19-21 very good
22-26 excellent, fantastic
27+ too much sugar starts to mask the flavor
30-32 brix in nectarines is where I’ve seen off flavors develop when there was too much water deficit. Sweet cherries are still good off the scale, 32+
Maybe you have a drier site than Alan? More heat or soil that holds less water?
More heat: yes, Wilmington, DE is hotter than south NY. Drier Soil: probably not, mine was clay, but all my trees were in 1’ raised beds; not sure if it made a significant difference.
The one nectarine that measured 27 was not bad, what I meant is that sugar started dominating the taste/flavor not leaving enough perception of other flavor elements. At 22-26, both sugars and flavor were well balanced. Below is a photo of a 27 brix nectarine, it’s flesh looks more like that of a plum .
Yes, if you have hard time raising the brix of peaches, I would have no hope at all! A good peach here is 15-16 Brix, and that’s probably as good as it gets. If I lived in Sacramento or the Central Valley, I would probably grow half a dozen peach varieties, but here they are not worth my time, effort or land.
Back to Alan’s question. My plan would be to open up the canopy and thin really hard early on. That’s how I’d max out brix whether you have good control of water or not. The sweetest fruit is always in the top of the tree. Try to make the whole tree like the top or just eat the top fruit or thin off all the bottom fruit.
There is one question that keeps popping into my head as I thin.
There are times when my fruit “bunch up” on one area of a scaffold while the rest is pretty bare. Or, sometimes, one branch/scaffold is loaded and while the other is bare.
I don’t know if this condition is exacerbated by the espalier method or just that it becomes more apparent on espalier.
So… is brix determined by the number of leaves near the fruit or by the overall number of leaves. Does the overall ratio of leaves to fruit control? Or is it the leaf/fruit ratio of the leaves near the fruit more important.
So can we leave fruits closer on one branch when the other is bare?
Will the leaves on bare scaffolds provide “brix power” to fruits on others or does the energy they produce go into storage or into vegetative growth?
Sorry for the long winded set up to the questions.
Has anyone here tried spreading wood ash gathered from the fireplace (or any other ash)? I’ve always known it to be the alternative to using potash which seemed to work on trees I’ve experimented with back in the tropics.
I burn a fire in a wood burning stove all winter and much of fall and spring and use most of my ashes on establishing trees. You have to be careful with them- obviously it’s like spreading lime and quickly jacks up the pH, but I believe that all the potash it contains can block an apple tree’s ability to absorb calcium.
I’m not sure but would think that there would be at least some transfer of carbohydrates from one area of the tree to another. But if you really want the highest quality fruit take out the branch with no fruits to let in more light to what remains. Most people can’t thin enough no matter what. It’s hard for me also and I don’t need much fruit.
I understanf the concept, but it would not apply to me because all my scaffolds have the same access to the sun as they are espaliered.
I will look for an opportunity to test when next it happens, I will thin one branch/scaffold viciously hard and the other
to the standard and test the results.
I think I have read growers on here like Olpea (sorry if I am butchering their screen name) take out fruit so it is only about 1 fruit for about every 12 inches. Most commercials farmers supposedly do 1 per 8 inches. Also many farmers will train peach trees so they are open allowing for sun exposure. Here in Colorado we are lucky with fruit trees or peaches assuming a freeze does not take things off. We only get about 15 inches of moisture a year. In fact our Palisade peaches catch a high bargain at 2 something a pound.
It’s amazing how much research remains to be done about how fruit gets its sugar-, just the basic knowledge of how far away leaves can be and still shuttle carbohydrate to fruit should have been established a century ago, but I’ve never seen any specific research on the subject. However, if you look at what fruitnut says and what most of us already know about shaded fruit, it is clear the distance cannot be far as shaded fruit clearly is not being served by fairly close leaves that are getting good light. So you need to thin those clusters of fruit but no one can tell you quite how much.
The literature does often suggest that well managed espaliers produce high quality fruit, although some research says summer pruning can reduce brix, without explaining why. My hunch is that it depends on the kind of summer pruning, but it could also have to do with how much water is in the ground- that reducing transpiration leaves more water to go into fruit, diluting its sugar.
I learned fairly recently that too much shade permanently destroys a leave’s ability to perform photosynthesis, so if leaves are shaded too long that are the ones that serve the fruit, brix would seem likely to decline, suggesting it is about judicious and timely summer or even spring pruning if you are trying to help fruit reach max sweetness. I do a lot of spring pruning of watersprouts coming out of big wood, but for apples this is also about assuring annual production. I wish I knew how much shade for how long destroys the functionality of leaves.
The rule of thumb that 30 leaves are necessary to produce the highest quality piece of fruit is probably an exaggeration depending on the relative light exposure of those leaves. All the leaves in an espalier are fully exposed to sun- when there is sun. And what about what sugar the fruit itself produces through its own photosynthesis?
Fruitnut’s suggestion to thin early and hard has long been my rule, but I don’t think any of us knows exactly the affect on brix if thinning is delayed. All the sun in the world early in the fruit’s development seems to have no affect on its sweetness at the point of harvest- it’s mostly about the last 2 or 3 weeks. Why would thinning be any different? Doing it early may only increase size and not sugar although the question about cell division occurring early in a fruit’s development adds another twist. Size increases early in development of fruit via more rapid cell division- later size increase is the result of bigger cells. Or so the literature says. I’ve read that more cells relative to fruit size improves fruit flavor. Ample water early increases cell division, incidentally and I doubt it affects eventual brix.
All this could be easily sorted out with some pretty basic research, but it would best to be done where it doesn’t rain and the skies are blue almost every day- but next season I plan to do some here in NY anyway.
Just the questions that you raised in your last post lead to a quagmire of interlocking interdependent factors.
Some that I id’d are:
How early or late to thin?
How early or late to prune for light on the fruit? on the surrounding leaves?
Tracing nutrient contribution from distant leaves?
Effect of water availability - Early, middle, right before ripening, during ripening.
Since we cannot control the weather (temps, light, water), the factors that we backyarders can work on is basically when and how hard to thin & to prune.
With my espaliers, I can more easily isolate specific sections of the SAME tree to see the effects of thinning & pruning.
I could prune the upper left scaffold as usual but not the right at all.
I could EARLY thin the middle left scaffold to 6 inches but the right to 10.(or whatever)
I could then re-thin the middle left buy not the right
I could LATER thin the lower left scaffold but not the right.
This might give, at least, an initial indication of the effects
If I send you a list of different apple & pear trees/varieties available, would you be able to design a VERY BASIC set of study parameters that I might be able to follow and not screw up too badly just as a start to eliminating or understanding some of the more important factors?
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