Is any higher zone plant a candidate for a sun trap species?

I'm planning out some sun traps in my field.  I'm zone 4a.  Can I assume that any zone 5 or 6 plant is a possibility or is there a way to whittle down the candidates?  I'd love to try a bunch and see what makes it but I'd rather start with some science to improve my chances.

For instance, I know peaches are "hardy" in my area but they often lose their blossoms to frost.  So I planted them in an area that gets shade from nearby trees and holds snow cover for an extra two weeks into the spring.  My hope is that the snow cover tricks the peaches into blooming later.  If I put those peaches in a sun trap I would think they would wake up earlier and be more likely to lose their blossoms in a freeze.  I am assuming a sun trap will help warm the area during the day, and any thermal mass I include will help at night but not enough to prevent a freeze if it gets to 20F overnight.

Another consideration is that a sun trap will melt the snow in the late winter.  So I lose the insulating blanket on the soil.  I suspect that my ground only freezes a bit in the fall before the snow arrives.  Then it's protected from freezing until spring.  So might a sun trap that causes bare ground induce more frost in the soil?  Maybe zone 6 plants are used to that and I'm worrying about nothing?

I'm assuming some plants hardiness is limited by their branches getting too cold and killing them.  I assume other plants don't care how cold the air is as long as their roots don't freeze down past a certain depth.

Is there a way to know which plants are affected by which killing condition?  Hopefully I'm overthinking this and any zone 5/6 plant is worth trying...

Thanks and sorry for the rambling...

If you love sun traps and want maximum temperatures, maximise south-facing walls, hard paving and gravel - and avoid greenery.The former will encourage absorption of the sun's rays and keep radiating them through the evening and night. You will probably need to add a vine-covered pergola to cool you down!

May I assume this is what you are referring to.

Peach and other fruit trees really benefit from a misting of water on the blooms as the temperatures dip after the bloom begins, This is how almost all fruit farms protect their crop when a late frost occurs because it works.

Since the whole purpose of a "Sun Trap" is to maximize the warmth of the sun, these spaces should be thought of more like a greenhouse or high tunnel than as an open garden space.

Many of the people who use suntraps in England will place a cover over the area when the temps are going to dip low, that traps in the heat from their thermal mass and that keeps the area warmer.
They will also make sure to have wind breaks in place.

Redhawk

Thanks Bryant, maybe I'm getting my terms confused.  I'm hoping to avoid needing protection on cold nights.  I'm trying to create a zone 5 or 6 microclimate in my zone 4a homestead.  My house has south facing sides that I could use but unfortunately they are shaded.  I have a sunny block retaining wall that faces south and I can put some plants there.  What I'd like to do is create some spots in my field to also fit some zone 5 or 6 plants.  There is a row of pine trees to the North to block some of the winter wind.  The only additional protection I can give them is a small berm, plant them in a depression, maybe a wood wall to the North of them, possibly a snow trapping shrub on the upwind side and possibly a snow shading plant on the South side to keep the insulating snow blanket on the target plant.

So I'm curious if I need all of those additions for any zone 5 plant or if I can somehow figure out which zone 5 plants can handle which combination of protection schemes.

I'm totally making up these examples but here's what I'm after:
Fig can handle cold as long as its roots don't freeze so if I trap snow around them they will survive to -25F.
Agave can handle frozen roots as long as its top doesn't get below 0F so if I block wind and radiate heat at night it will be fine.  So trapping snow would not be needed and I can place rocks around it to hold more heat.  Maybe reflect more sun onto the rocks as well.
Once again, these are made up examples so that I could get the idea across

Thanks!

You can probably do that with success, your plan is sound.  In Germany they came up with the Hugel mound design to do that exact thing, but that is probably only one of several methods that will work.

Redhawk