Trees at the bottom of a North slope

I am planing an orchard. Unfortunately, I have to work with a north slope, and the bottom of the slope gets more light. I am in Colorado, so I have a dry climate, with very erratic and unpredictable temperature swings. Late frost damage can be problematic. The bottom of the north slope has a high water table and an irrigation ditch, which overflows in rain storms. So it is an oasis, perhaps too much of one. The west, north, and east sides of the field are surrounded by volunteer cottonwoods, some of them in rather bad shape.

I have several questions:

What useful trees bloom late enough to be planted in the frost pocket? I was wondering about late blooming apples. Anything I plant has got to be reasonably standard, since this is a community farm and we don't want to risk planting large amounts of unusual plants. (Though we will be experimenting on the side. Siberian pea shrub, hardy kiwi, lots of perennial herbaceous plants, possibly honey locust, etc.)

Anything will sleep later than normal on this north slope. So will the aspect help to cancel out the disadvantage of the low elevation?

To get around the drainage problem, I plan to build two foot mounds of soil by digging a circular trench, piling the soil in the middle (separating out the top soil and sub soil) and then using the trench as the base for a circular hugelkultur tight against the slope of the mound, and rising above it, so that the whole thing looks like a volcano with a tree sprouting out of it. The "crater" will keep in water for the first few years, till the wood rots and subsides. It should also provide fungi dominated soil for the trees. I will use rocks around the rim to hold heat (there is a lot of solar power here.)

Is this a good idea, or am I missing some sort of problem?

And, should I leave the cottonwoods in place to trap heat near the ground, reflect light, and slow wind (not to much of a problem in this dense suburban area, with tons of trees and houses around.) Or should I cut them, so they don't steal water, nutrients, and light? In which case I would plant something smaller and more useful. (The cottonwoods are not old growth, just weedy volunteers. Maybe forty years old. ) The field is 225 feet wide, but I need to plant trees, if I plant them at all, mostly in the western corner, so the cottonwoods would be on the north and west sides.

Thanks ahead of time for the advice.

Late frosts can play havoc with fruit trees.
Perhaps, the north slope will actually help prevent premature blossoming, thus mitigating the problem.

It is a common practice in many northern European orchards to lime wash the tree trunks to delay early blossoming.
It delays when the tree will break dormancy, often saving the crop.
You want enough air circulation to prevent frosts from lingering around your trees - wind breaks could work against you.

John mentioned late blossoming and the advantage of not having them frosted off. Many apples require a long season, so you'd want to make sure that you don't push cropping too far toward fall frost.

Plums generally have a shorter season and they deal with waterlogging better than other fruit.

Many berry crops can benefit from late blossoms both as insurance against late frost and in order to get a crop long after other berries are done for the year. I often harvest Himalaya berries from south slopes in July and as late as November on north slopes. Sepp Holzer stretches his cherry harvest over months by planting at varying altitudes. Most of us don't have that option, but a bit of slope can make a big difference in timing the harvest.

For berries, it might also be wise to consider what birds are eating. When huge amounts of wild berries are available, there is less pressure on cultivated berries. By timing to match natural abundance, serious pests are naturally neutralized since they prefer the wild stuff.

If they are not "too weird" for you people and your climate will permit them, mulberry and persimmon bloom later than other fruits, and both do not mind occasional wet, the mulberry so much so that I would think the hugel-mounds unnecessary for it. What about nuts? Most of those bloom late, and some like pecan and hazelnut, are bottomland trees.....

Not a fruit tree; but a small stand of willow for annual coppice, might do well there? Willow has many uses

Hello everyone,

Thanks for the advice. I'd like to plant mulberries, and pecans. Willows would also be interesting.

That brings up an interesting point. I am in zone five/ six, depending on what you read. We have an average of 130 frost free days. Supposedly, there are pecans which can tolerate these conditions. Does anyone know of any successes with these along the front range, or similar climates?