Late blooming fruit trees, frost and microclimates

Hello, I've been perusing this forum extensively and watching a lot of Sepp Holzer videos to help figure out the vexing issue of late blooming fruit trees. I live in Goldendale, Washington at 2700' elevation and have used this handy chart provided by Washington State University to help assess why my fruit trees are not actually fruiting after bloom: https://extension.usu.edu/productionhort/fruit/tree/CriticalTemperaturesFrostDamageFruitTrees.pdf .

Our fruit trees, in general, will break bud in late March, early April and by May be flowering and ready to pollinate. In May, we are subject to late frosts breaking that 32 degree Fahrenheit mark that will damage the bloom. I would like to create microclimates in my garden to somehow help the tree survive and stay above that 32 degree Fahrenheit mark. Three ideas that have stood out to me:

1. Pouring boiling water into a bucket assigned to each tree. However, this is quite an endeavor and energy expenditure for 30+ fruit trees.
2. Using stones as a heat sink for each tree and hoping and praying they release enough heat at night to keep the trees immediate area above 32 degrees Fahrenheit.
3. Using small ponds and/or other bodies of water to reflect heat and hold and release heat.

Number 3 seems the most intriguing at this time. My question is, is there a formula for this? What I mean is, how big should the pond be? How deep should it be? Should there be a specific position of the pond in relation to the tree in order to absorb and release the heat in the most effective manner? I know Sepp Holzer uses a similar method, but again, it's very esoteric so having a concrete example would be quite helpful. I appreciate all you wiseheads and your extensive knowledge on these subjects. Thank you!

If you can get some very dark colored stones that can absorb heat during the day and give it off at night.  Or even used concrete blocks painted black.  This may be enough in some late frosts.

I have seen previous examples of black barrel of water under the south side of the tree allowed blooms above it to survive.   Because my peach trees are susceptible to leaf curl I used portable garage frame to make a high tunnel over them.  With mason bees in side this resulted in early and heavy fruit set.

This is an interesting concept, simply using a black barrel. I would stick it out under the tree with cheese cloth over winter so I wouldn't have to tap the well to fill it. How many gallons were these barrels? Did height or width make a difference? Thank you

I suspect placing these stones in a south facing manner, much like solar panels would be most useful? Stones compared to black barrels full of water, which would be more effective? Or is the jury still out?

Bernie Clark wrote:This is an interesting concept, simply using a black barrel. I would stick it out under the tree with cheese cloth over winter so I wouldn't have to tap the well to fill it. How many gallons were these barrels? Did height or width make a difference? Thank you

  The example I remember was a blue 55 gallon barrel not intentionally left under the tree but the results were noted in true permaculture fashion.  The blue is not bad because that means it absorbs all but the blue which is already scattered bey the atmosphere.   If you have a slow well having the water stored for the summer would be an advantage.  I have 3 in my greenhouse one black and 2 blue and the color does not seem to make much difference.
commercial orchards use sprinklers to come on at freezing point so the water freezes instead of the blossoms.

Finding varieties that have frost resistant flowers and are later blooming may be easier and have better long term results than trying to protect more susceptible varieties from late frost. I have a few susceptible varieties, and they are hard to help no matter what is done for them.

Stone fruit are the main ones here that usually get damaged the most with late frosts. I used to look for varieties that bloomed later, but after growing them for a while, it seems that having frost resistant blooms can be far more important than flowering time.

Usually the different varieties only differ in bloom time by a week or two anyways, and I still prefer the later bloomers if possible, but even the frost tolerant varieties that are earlier bloomers do better than more susceptible late blooming varieties.

Here's the flowers of Reliance, one peach that has very frost tolerant flowers. Its blooms are are both late blooming and very frost tolerant. I plan to use it in breeding locally adapted frost resistant varieties.

Try growing Jujube. It is a stone fruit.  Late blooming and has few insect or disease concerns.  Needs full sun and a lot of water.