Here is one way to create a cooler microclimate effect:
This is the hedgerow down the hill, on the coldest part of Ladera Frutal, where I have my corralito planted with deciduous fruit trees. In a low-chill region, one can maximize one’s chances of getting fruit by “cheating” on the chill hours. One way to do that is to plant one’s highest-chill varieties (like the cherry and apricot varieties depicted here) in an area where they will be shaded in the winter. Naturally, one has to avoid the trees’ being shaded in summer, when sunlight is needed to ripen the fruit.
One way to accomplish this is to plant close to taller evergreens, as with the mature Marsh grapeftuit trees than can be seen on the exterior of the corralito. When the sun is low in the sky, as on this first full day of winter, only the tops of the trees will be in sun. But when the sun is higher in the sky in summer, three trees will be bathed in sunlight except at their very low back sides.
The hedgerow style of planting itself helps with the chill, because the dense planting trees help trap cold air (further aided by the groundcover seen here), while the dwarfing that results from the trees’ crowding one another keeps most of the fruiting buds low to the ground. The ground remains significantly colder in winter than the air a few feet above. After I prune this hedgerow in the coming weeks, all the trees will be shorter, as I will leave only the low branches.
Along this hedgerow, the overnight temperatures often can be a degree or two colder at night than is the case out in the open, and the shade keeps the daytime high a few degrees cooler, too. A few degrees here and there, over three months, can add up to a hundred or more chill hours, making the difference between no fruit and a good set on varieties marginal to one’s climate.