can I space trees closer on slope? effects of east-facing slope?

We've been looking for the right piece of land to establish a mixed nut and fruit orchard, and I have some questions about orchard spacing and sunlight that I can't figure out.

I was hoping for at least 7 or 8 acres of land to accommodate the number of trees we wanted to plant, at the spacing recommended in the books. There's a property on the market that seems otherwise to tick most of the boxes on our wish list but is a little small, 5.6 acres. It slopes to the east, so it catches the morning sun but the ground continues to rise to the west so there would be less afternoon sun. The slope is approximately 15 percent. I'm wondering if spacing requirements change on a slope, perhaps making it possible to fit our planned orchard into the space available on that property.

My understanding of the spacing recommendations in the books is they are intended to allow all sides of the crown to intercept maximum light without interference from the other trees. I can picture how this would work on flat or somewhat flat ground. But does spacing change on a slope, and if so, how?

On the property I described, the trees would be in north-south rows so going east to west, each row would be higher than the row before. So the rows could possibly be spaced closer without intercepting the next row's morning light. In the afternoon, the shadow of the hill to the west would intercept some of the afternoon light anyway, plus each row to the east would be shaded by the row above it.

Most books I have read that reference planting on a slope talk about either a northern or southern exposure. Is an eastern exposure potentially a problem? I should mention that our main cash crops will be chestnuts, hazelnuts and elderberries - the hazels and elderberries along with smaller plants will form an understory between chestnuts. My spacing question is really for the chestnut overstory. We plan to harvest by hand or nutwizard, so we don't need to leave space for harvester equipment. Also, about the site and its shade, the next door property with identical exposure has a successful apple orchard - I'm not sure if light requirements are similar.

So, to summarize, my questions are:
(1) what is the effect, if any, of that 15% slope on plant spacing? Can we plant closer, fitting our planting plan into a smaller space?
(2) is the east-facing slope okay, or should I be looking for a different exposure?

I'm really finding it hard to wrap my head around this one and look forward to your feedback. Thanks.

At a 15% grade (7 1/2 foot rise over 50 foot distance) you will gain an extra 1/2 a foot of land area for every fifty feet as compared to a flat surface.  Not much of a gain but some gain.  If you trained the upper trees taller and trimmed the lower ones shorter over time you can exaggerate that height difference allowing more of the canopies on the upper side to be in more direct sunlight by being a bit taller than the lower canopies, that could gain a bit as well.

As for trees close together, while my forests are pine/fir and spruce they were planted 40 years ago in rows spaced at 4 feet apart.  Now 35 to 40 years later I have a lot of trees 18 to 24 inches in diameter literally spaced four feet apart on center from one another.  Tree spacing has it's wisdom, but trees can still grow pretty well even when spaced closer than they should be.

Even at say a 30 foot by 30 foot spacing per fruit tree that is still only 900 square feet a tree or "48" trees per acre, that is quite an orchard potential on just a few acres...  My forests have around admittedly "evergreen" forests so not quite the same thing, but I am running just over 1,000 trees an acre with 40 year old trees all of them 40 to 50 feet tall.

You can actually fit a surprisingly large number of trees into a small area of land, you could fit over 3,000 40 year old evergreen trees into "3" acres on your place, my bet is you could fit quite a few fruit trees as well.

P.S

As for eastern slope, "all" of my place is on an eastern slope, though my slope is much greater than 15% mine averages between 30% to 40% depending on where you are.  I doubt that it makes much difference between Eastern slope and Western slope.  Eastern slope should better than a Northern slope and not as good as a Southern slope.

Your situation sounds a bit like the southeast facing place I am moving onto. My experience comes more as a naturalist and having hiked from Mexico to Canada with the effect of aspect on vegetation in mind as I observed radical changes from one side of a ridgeline to the other. Mollison also talks about this in his big black book. I’d also recommend reading Restoration Agriculture by Mark Shepherd if you’d like permission to throw spacing worries right out the window.

In general, fruit bearing plants benefit from an east facing slope, especially in northern pacific coast climates where mildew and molds are concerns. This is because the sun hits them earlier, reducing the amount of time dew or frost will linger and harbor fungal disease.  The exception to this is in deserts where fungus is not much of a problem and  dew is virtually the only moisture, so you want it sticking around. So the east facing slope will be a positive. I am not sure if you have similar East wind phenomena up there on an island, but for us eastern winds bring more extreme temps (high and low) and are generally dry from coming off the inland deserts rather than the ocean. That would seem a good thing for Mediterranean and steppe plants like many  prunus and apples.

I’d also wonder what your overall goals are. Is this meant to be a business or a homestead? If the latter, you will be rolling in fruits and nuts with the space you have, and could interplant vines and understory plantings at wilder spacing, but could also get away with much tighter spacing if you are not depending on harvesting equipment. I’d only hesitate on tighter spacing if sun is limited in your climate and fungal disease is a major problem due to humidity. Otherwise, the shade on the soil from tighter spacing will mitigate moisture stress as much as it may cause root competition, and trees have evolved in forests, where they have to coexist with other plants and often can benefit from them. Good luck, and enjoy your journey!

Thanks Roy and Ben.  

It's good to hear that an east-facing slope can work. And in relation to training trees taller/shorter, I have about 8 different chestnut varieties (grafted trees) in pots in my back yard, and it might be feasible to position them on the slope with the shorter-growing varieties in lower rows so as to block less light for the upper rows.

We're in a bit of a rain shadow from western winds but eastern winds pick up moisture crossing the water from the mainland. That said, there is very little moisture here during the growing season. It all comes down as rain during the winter.  We plan to install a pond to capture winter rain and pump it back up to a system of swales and berms using a solar pump in summer.  I'd forgotten about planting close to shade the soil and retain moisture in summer, so that is something worth thinking about in this process of determining exactly how much acreage we need to meet our goals and how it needs to be configured.

Ben, Mark Shepard's book is what started me on this journey and then I read H. Russell Smith's 1929 book Tree Crops and was completely hooked.  

Re goals for the property and plantings, it will be a mix of homestead and a few cash crops to pay the bills, which will be perennial tree crops.  I am going into business with my daughter who is 21 and wants to farm as a career choice, but at a scale that is more like an expanded homestead, not big ag. Initially I'll be supporting the mortgage and farm costs by continuing to work in my present job, but we expect to have some farm income established by the time I retire in a few years and eventually the new farm will need to be self-sustaining. So a certain minimum acreage of perennial cash crops is part of our planning to provide an income.

Right now we have close to 1000 pots of perennial food plants growing at my present 3 acre place, mostly species we're growing up from seeds or cuttings to get some size on them before we transplant them to their permanent home. She's booted my geese out of their paddock into a smaller pen and has started turning their former space into a spot where she will plant a market garden this year. We're also planning on selling plants at the market, including some of the propagated perennial food plants. That's assuming there is a farmer's market this year with coronavirus...but if that is too much potential contact for people, we can sell from a farm stand. There is a well established honour-box system here and I suspect buying food from a farm stand in an open air venue where the food is local, has been handled by only one or two people, and you don't even have to see the seller will be even more popular going forward.

Of the 1000 or so pots out in the yard, 400 are grafted chestnuts of European x Japanese named varieties. These are going to be the backbone of the cash crops on the new property. Because they were rather pricey to buy, I am hoping to be able to give them plenty of space and keep them all (except for some that we might sell at market this year) rather than crowding them and then keeping the ones that do best according to the Shepard STUN method of natural selection.  I can see that being a viable method for seedlings, but since these are grafted trees of commercially grown varieties the performance should be reasonably predictable.

Along with the main crops of chestnut to be underplanted with hazelnut and elderberry, we have a bunch of other things already growing in our pots that will get planted in the rows - raspberries, tayberries, loganberries, red and white currants, goji, haskap, basket willows, pussywillow, figs, old roses, asparagus, Egyptian onion, horseradish, lots of perennial herbs, and a lot more I can't think of just now. We also have some Northern pecans, heartnuts, persimmons, pawpaws, apples, cherries, plums, linden, a shipova, and Korean pine. And 2 baby giant sequoia, just because :) Lots of other things that are presently cold-stratifying and hopefully will come up in spring, like mulberry, more Korean pine, cherry-plums, honey locust, etc.  In the alleys between rows, we're going to run laying hens (expanding my existing flock which currently number 23) in chicken tractors, and in alternate rows will grow annual or perennial crops including flowers for bouquets.  The idea is to keep every other alley (the one that can be grazed) accessible by truck and tractor so trees can be reached on one side, the other side is in market garden crops. As the tree canopy starts to fill in, which realistically is 10-15 or more years, non-shade-tolerant vegetables and flowers will be grown only in a vegetable area near the house and the alleys can be switched over to grazing, but by that time the trees will be producing and market gardening will not be the primary income stream. Once the plants go in the ground we'll be mulching with wood chips and will plant stropharia mushrooms and once there is some shade will start inoculating logs with oyster mushrooms.

Lots to do, and I think I had better go do some of it now! It's a busy time of year and once things slow down a bit I think I should take some photos and start a thread to document the process.  

Sounds like you have an awesome plan, I’d trust your instincts and buy when the market is low if you can!

I suspect that all the suggestions for tree spacing operate on the supposition that you will harvest *commercially*. When you look at a 'wild'  forest, how closely do they really grow and thrive? Some permies make rows so they can plant more bushes in between the trees. It sounds like a good compromise: You can still run equipment between the rows one way but have the rows themselves planted "solid". It may not have the "look" of a food "forest", yet it should function pretty close to the same.
When I started my apple orchards I ran them 20 ft in both directions [N-S/ E-W]. Now, I'm inter-planting, trying to make guilds, but still preserving a N-S direction for the 4 wheeler. [In this direction, the solid rows can also trap the winter snows, which in sandy soils is important. Depending on the type of soil you have, you may want to orient your rows for water/ soil conservation? To avoid erosion?
Since you will be dealing with nut trees, however, perhaps a different consideration might be: Will it be possible to grow "solid" rows near some nut trees? Black walnut is famous for its allelopathy, but there are others:
https://www.gardeningknowhow.com/garden-how-to/info/allelopathic-plants.htm
Good luck to you. Let us know how it turns out.

I think this is awesome. I am doing this on a much smaller scale. One thing that came to my mind is longevity of trees and their growth rate. In my climate, pecans are the main nut tree. Their slow growth allows me to grow peaches between them. At the point they get shaded out they will probably be past prime but is a good smoking wood. Also, the peaches will give me a harvest as i wait a decade for pecans.

Besides the trees, i am blitzing the "in betweens" with every shrub, herb, perrenial, nitrogen fixer i can get my hands on. Where the soil is thin and rocky i am planting lavender and native persimmons. I will know what wants to be there and what doesn't. The evolution of what it will become is exciting as it may be different than my vision.

Thanks Cecile and Wayne, those are good ideas.

Our main nut trees will be chestnuts, so allelopathy will not be a consideration for them. I do want to plant a smaller number of walnuts, but it will depend on how much land we are ultimately able to acquire. It may only be a few walnut trees. Most people here (coastal BC) grow English walnuts (aka Persian or carpathian, I believe); I grew up with black walnuts in eastern Canada, and would like to have a few of those. There are quite a few things we can underplant with walnuts, or I may plant a grove of black walnuts very close and thin them out for lumber as they grow. I also have, already, a few young heartnuts in pots and am really looking forward to see what interesting nut shapes we get from those eventually. They are in the walnut family but my understanding is the allelopathy is minimal or absent.

As water management is a major consideration here, we will be planting on contour and using earthworks to direct the winter water to a pond from which it can be pumped in the dry season. This will be the primary factor determining layout, actually, rather than orientation to the sun.

We will definitely be underplanting and interplanting the rows with the maximum diversity of permie style plants that will flourish in our climate and can handle shade or semi-shade. Your idea of planting short-lived trees that would be removed is very good. I don't have any of those factored into the plan yet, although have some pawpaws that I want to trial. They are shorter lived, although if they do well I would really like them to live longer! In their native range they grow well as an understory tree, but I suspect will need full sun to fruit here as our summers are so cool. The interplantings may complicate collection of nuts that have to be collected from the ground but we are planning to harvest using a nutwizard or similar and may then have to finish picking up by hand. The other option would be to underplant with things that can be harvested and/or cut to ground level before the nuts come down in the fall. Ramps, if I can grow them here, and other spring ephemerals (maybe daffodils and tulips as spring cash crops) would be good as they will disappear by the time of the fall nut harvest. I don't really want to go the route of just underplanting with things that I cut down by fall, or just planting turf as seems to be the common thing in commercial orchards (or bare ground, which horrifies me!), as I want it to be more like a series of linear forest gardens.

I have been thinking that Dutch white clover would make a good nitrogen-fixing ground cover. Probably mixed with other low-growers such as chamomile, heal-all, etc.  We are also planning to plant some woody nitrogen fixers too, such as honey locust (I am thinking no black locust as they spread so invasively here), sea buckthorn, etc. I also just realized that licorice root (Glycorrhiza) is a legume and nitrogen fixer, and am just about to order some seed - they should be a good perennial nitrogen fixer, the plants are harvested in year 3 for the roots, but they regrow from bits of root left behind and the leaves also can be made into tea. We are drinking a lot of purchased licorice root just now because it is a strong anti-viral, immune support plant and specifically is used for respiratory issues. Also, there is scientific evidence (paper published in The Lancet) that it is effective against SARS viruses. I wish I already had lots and lots of this one now! We will plant in big pots so it can go with us when we move. The plant gets to be 5 feet tall, apparently, so I'm picturing it looking like a very large white alfalfa. I think it will fit very well into our long term plan. I haven't seen much information about using the leaves, they do not appear to be commercially available as tea although are drunk as tea in some parts of the world, and make good fodder (and have been shown to be anti-viral for poultry too).