I am setting up a fairly large permaculture orchard on a dead flat piece of property. No trees or buildings, just grass, with good solar access and a water source. (The whole site will be a community garden eventually.)
Here in Colorado, the main problems with growing fruit trees are a lack of water and an erratic climate. The lack of water is fairly simple. The erratic climate is more complicated. For an example, it was 68 degrees F today, and will not freeze tonight. This kind of weather has been going for a few days, and will continue for a few days more. However, we will continue to get frosts till June 1st, and it would not be unusual if the day after tomorrow it was 15 degrees F for a high. We had three days below freezing in a row, with the lows under zero, at the beginning of November this year. And our first frost was before the end of September.
This stresses fruit trees tremendously. They tend to dehydrate during warm winter spells, they tend to flower early and get frosted, the trunks get sun scald, and they leaf out early only to get a dump of snow on top of them and snap.
So I plan to put in long hugelkulture mounds running East and West, digging down about two feet and piling them up three feet above ground. Then I will plant the trees at the base of the mound to the NORTH of the hugel mounds. Each will have a berm with some of the extra top soil around it to hold irrigation and rain water.
My hope is that the northern location will keep the ground around the roots and the lower trunk cool and moist, delaying flowering and preventing dehydration. The fungi and decomposing wood to one side of them should also be helpful, and be a store of water they can tap.
I know that the top of the mound will probably be rather dry in this climate, but I intend to plant hardy drought tolerant nitrogen fixing shrubs on top of it to help the shading effect and provide mulch for the trees.
In front of the mounds I will plant fruit and nut bushes which are not so prone to early flowering, again planting valuable plants right where the slope starts, to avoid having them sink over time.
There will be wide alleys between the rows of trees/ hugelkultures, so that I can bring in truck loads of mulch, mow the grass/ ground cover easily, and run chicken tractors through. I will plant a small area of sheet mulch around each tree with a guild, which will slowly expand over time as I expand the mulch rings and the grass gets shaded out.
I don't know if you mentioned it or not, but you might want to look at adding some small pocket type ponds. Chances are there is some sort of slope (however minimal) and you could take advantage of that to hold more of the moisture that falls on the land. This would have the added benefit of increased micro-climate stabilization. Other than that it looks like a sound plan.
Hau, Gilbert, It sounds like a good plan. Like Dave mentioned, you might want to make some water holding depressions (ponds). Do check to see if there is any slope, no matter how small, if there is it is something to be used to advantage a-la swale in front of hugel berm. The plan you have given will provide many micro climates. Keep us up to date on the progress please.
Great idea, the one thing that stood out is how far apart you planned the hugels. Tighter spacing creates a more distinct protected microclimate and wind/evaporation reduction. I found a significant difference in my grape bud break timing between the 4 successive rows on just two perpendicular arching E-W beds (each 4ft wide w/3ft paths). I can only imagine this is related to temperature differences. The healthiest, earliest grapes are on the 3rd row from the front/South, on the south side of the 2nd bed. This is the most protected spot from wind (our main stressor other than mold) and has the most stable microclimate. I imagine these things are even more important where you are in the rockies versus my ultra temperate climate. Then again, this is just my third season with hugels and I am far from an expert. I may consider a way like a large scale key hole design to allow a vehicle in to add organic matter that still allows for as little path space as possible. So maybe one or a few central "roads" with more like cart width paths branching off. Just a thought. Great idea and best of luck!
This is all just my opinion based on a flawed memory