I don’t think it is something that happens especially in my climate and after doing a quick CHAT search I realize that the causes for this one time occurrence (I misworded it when I said there are even year- but hey, I didn’t put in an s!) were likely related to the relative frost hardiness of specific varieties at the time of the event. There are 3 possible reasons this can happen, as I recall, but not really worth the effort of going into since it isn’t relevant to the discussion. The varieties that flowered later probably would have been better off if they’d flowered later still.
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@Olpea I don’t think you should finish your trial at bloom time! The study found a difference in kg fruit per tree even though the bloom was not significantly delayed by the white latex paint.
Also like @JDN they sprayed with new white (interior flat) latex paint. It was slightly thicker- diluted 5 parts water to 1 part paint instead of 8:1.
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I wanted to report back my initial findings of my very small paint experiment. So far, I don’t think I’ve seen a lot of difference. The painted trees seemed to delay bloom by only a couple days vs. unpainted trees of the same variety. I had hoped for more.
The caveat is that it wasn’t truly white paint, just very light colored paint. Additionally, I didn’t put it on during first dormancy (as is recommended, I believe).
I’m still waiting on the part of the evaluation, to see if there is any difference in fruit quantity of the painted trees vs. the unpainted ones.
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Thanks for the update.
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I think it may offer benefits beyond just delaying bloom—it likely helps protect buds during cold spells, leading to better fruit set. Of course, that won’t matter much in a freeze severe enough to kill most or all of the buds, but could be a big help in other situations. Interested to see the final results.
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I am actually seeing what looks like a bit more fruit set on the painted trees.
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Cool!!
A lot of the heat accumulation comes from direct sun exposure so another thing that might be worth trying is to block the sun with a high south wall or something.
I would also consider Surround with a bunch of sticker sprayed on the whole tree. Or maybe there is some lime spray that could last longer.
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Definitely a south facing wall is a great idea to delay early spring blooming
I didn’t do this intentionally but I have a peach (1) , plumcot (2) and apple (3) all within about 6 feet of a south facing vinyl wall and those 3 are the last of my trees to break dormancy. I would say they’re about 7 or so days behind my other trees. I’m definitely glad the plumcot is there. I will likely move soon but would definitely favor planting anything that blooms early (apricots, plums, some peaches) close to a south facing wall. They still get plenty of sun in the spring and summer once the sun is higher in the sky
Edit: I’m not sure if south facing wall is the correct verbiage. The wall is to the south of the trees so I guess it’s probably a north facing wall.
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I still think limewash or calcium carbonate would probably be more effective at delaying bloom. In addition to being breathable and reflective, they also have microcrystals that can scatter incoming light. This reduces the amount of energy converted into heat, keeping the tree cooler.
I was reading this complete thread as a newbie. Through it something kept shining out (sorry sun joke there).
I’ll say first, I’m of a Z3b/4a area that gets a nice amount of sun heat in spring, subjectively as a human, mixed in with far below freezing. As a reference many many Red/Sugar and other Maples split their bark. Thus, it’s a known thing to do to paint trunks (&just trunks.. fwiw?) of some of those trees. Also it’s notable white trunk birches seem to do this naturally, and light trunked Aspens, etc, too. Those native tree species having mid grey seem to depend on the thick, corky barks (Eg Balsam & Black Poplar) as insulators. So it’s almost indisputable something is going on.
The thing I’m thinking is: given a tree is a visible light “mechanism”- are we sure that putting a light blocking coat (white is best for well-understood reasons) for not just infrared but the visible light spectrum isn’t the “trick”?
Surely just below the waxy surface of tip growth there are cells that “do something” based on visible light? …and that might “flag” springs arrival?
So I’m saying do a thought experiment looking more at opacity, …more than reflection of heat per se. The two are almost the same, but not quite.
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I was out and took a photo of the trunk of my Mt Royal plum. Brilliantly shiny silver on south facing … all entirely on its own. 
Interestingly, much less so on north. I tried to take a photo of that, but auto exposure got it wrong- plus a bit of a sunflare.
(I should clarify that white on the ground is the last of our snow, so fairly bright white. Yes, still snow- we get frosts here until 3rd week of May. 53.5 latitude. Put it another way, the distance Oshkosh is from the US border, or parts of Yellowstone? Go that far North into Canada.)
Anyway, is this silvering tendency well documented/understood?
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That’s a really interesting observation. I think the silvery or lighter color on the south side is likely caused by light degrading darker compounds in the outer bark.
As for visible light triggering spring blooms, most research suggests that once chill hours have been met, heat accumulation is the primary driver rather than light intensity—though the two are definitely intertwined. The distinction between opacity and reflectivity is important for heat as well. A surface that is opaque but not reflective, like black paint, will increase heat accumulation, while one that is both opaque and reflective will reduce it. I emphasized breathability because it also allows trapped heat to escape, further decreasing overall heat buildup.
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