Reverse suntraps?

I'm thinking about using log rounds and earth to build suntraps in reverse; arcs about three feet high open to the North, with a fruit tree in the center. The arc would be small enough so that at the equinox the ground at the tree's base would be completely shaded. To add to the effect, I would shovel snow into the trap.

I'm hoping this will keep the soil cool enough to delay flowering, thus keeping my trees from flowering in early spring warm spells, while also keeping the soil damp longer.

Good or bad idea?

Interesting idea, Gilbert.  If you have enough trees, it might be interesting to do the experiment of encouraging snow build-up around some and compare them to others that don't.  
The following may apply to flowers as well, but I'm not entirely sure.

"Young and colleagues (Young and Werner 1985, Young et
al. 1987, Arnold and Young 1990, Young 1992) have extensively
investigated the effects of root temperature on the extent
and rate of bud break in apple and peach trees. For example,
Arnold and Young (1990) showed that the rate of bud break in
apple seedlings grown at a shoot/root temperature of 20/5 °C
was about 0.8% day– 1 compared with about 1.7% day–1 for
seedlings grown with both shoot and roots at 20 °C. Furthermore,
after 21 days, bud break of seedlings grown in the
20/5 °C treatment was about 20%, whereas in seedlings grown
in the 20/20 °C treatment, it was 35%, indicating that rootzone
temperature affects both the rate and extent of bud break.
By contrast, time of bud break in Scots pine seedlings was unaffected
by root-zone temperatures between 5 and 17 °C (Domisch
et al. 2001). Although time of bud break was not reported,
shoot growth of Populus tremuloides Michx.
commenced earlier and at a higher rate as root-zone temperatures
increased from 5 to 20 °C (Wan et al. 1999), which is
consistent with root temperature effects on bud break in other
species. Thus, for some species, there are marked effects of
root-zone temperature on bud break and shoot performance."

from:   http://treephys.oxfordjournals.org/content/26/1/105.full.pdf

Interesting concept...  I'm thinking about a similar but different idea to trick zone 5 trees into liking my zone 4 climate with sun traps.  I was just starting to think about how to encourage snow to drift onto the trees so I don't have to shovel it myself.  Sadly, despite living in Wisconsin, I'm not sure how to deliberately create a snow drift...

One thing to consider is that if the ground isn't frozen, the snow may act as an insulator.  Once the snow melts the ground will already be thawed.  It would be nifty to have a self managing system where the ground is barren until it's well frozen and then cover it with snow to lock in the cold.

My backup plan is to just build a tall curved hugel style berm on the North side of my trees with a pole so if I need to cover the tree to protect from frost I can just stand on the berm and throw a tarp over the pole to protect the tree.

Mike Jay wrote: I was just starting to think about how to encourage snow to drift onto the trees so I don't have to shovel it myself.  Sadly, despite living in Wisconsin, I'm not sure how to deliberately create a snow drift...

To encourage snow drifts, put up snow fence . That lovely orange mesh is supposed to catch the snow and make the drifts where you want them instead of the road or your driveway.

So would a hugel or berm do the same thing or do you need the porosity of a snow fence to make the magic happen?  Thanks!

I think it is the mesh. It has to do with the wind patterns too. If you are opposed to plastic I imagine lattice would work. Good luck catching snow

So a solution for Gilbert and me would be to plant a windbreak porous deciduous shrub on the windy side of the fruit tree so it can guide snow onto the base of the tree inside the sun trap.  Thanks Andrea!

I've used evergreen ground covers (English ivy) to delay spring shooting on bamboos.  The ground cover would delay shooting by about a week, enough to get past a late frost. Once the bamboo had spread enough to shade itself it didn't have much effect, but for new plantings where the sun could shine around the bamboos root zone it would delay shooting.

I built a reverse sunscoop as part of one of my hugel mounds with the same thought in mind.  The problem I ran into with our relatively heavy clay based soil up here in Idaho was too much water...the tree did great for the first summer, then just never came out of dormancy the next spring.  Poking around I found that just below the mulch the ground was completely saturated.  I was able to capture about 3 feet of snow in the scoop, but I think what happened was as it all melted off it killed my poor apricot tree!  If your soil drains really well it will probably work better though.