Fruit tree planting-distance guidelines: S wall micro-climate

South exposure walls provide a boost of warmth on sunny winter days. The warmth may allow forest gardeners to plant varieties that require fewer chill hours than the general region requires.

In my case, the recommended chill hours for fruit trees in my area is 1000-1200. I would like to plant an apricot tree, and the highest chill hours for an apricot tree is 800. It seems to me that planting near the S wall could take advantage of the heat that radiates from the wall and thus reduce the number of chill hours required.

However, I don’t want to plant so close to the wall that the daytime warmth causes the tree to come out of dormancy early. Stuccoed S exposure walls in the sunshine can be well over 100°F when daytime temperatures are in the 50’s or 60’s during the winter and spring months. Late frosts commonly kill off fruit, so protecting the trees from extreme fluctuations is also crucial.

I am eager to hear tips on how to work with passive solar gain near S walls to improve fruiting success.

Amy Gardener wrote:South exposure walls provide a boost of warmth on sunny winter days. The warmth may allow forest gardeners to plant varieties that require fewer chill hours than the general region requires.

In my case, the recommended chill hours for fruit trees in my area is 1000-1200. I would like to plant an apricot tree, and the highest chill hours for an apricot tree is 800. It seems to me that planting near the S wall could take advantage of the heat that radiates from the wall and thus reduce the number of chill hours required.

However, I don’t want to plant so close to the wall that the daytime warmth causes the tree to come out of dormancy early. Stuccoed S exposure walls in the sunshine can be well over 100°F when daytime temperatures are in the 50’s or 60’s during the winter and spring months. Late frosts commonly kill off fruit, so protecting the trees from extreme fluctuations is also crucial.

I am eager to hear tips on how to work with passive solar gain near S walls to improve fruiting success.

I too am curious. In my instance, I have against the home (an 1910's three story Vic) on the SW side and he wants Vines to shade the home in the summer sun. I'm trying to incorporate edible plants (zone 5b). I have suggested Akebia but they are unsure since not even I have ever had the fruit.
They are not wild about Schisandra. So if I can use the exposed foundation wall as a battery, I was thinking of trying Passiflora edulis. It's hardy to zone 6 so maybe I could squeek that by . . . I will be planting figs and cutting them down and mulching heavily (as I know of people colder than this town and they have all sort of fig varieties at least half out of doors).  
So thoughts on what kind of gain you may expect to see with a color change?
Does anyone know if that is worth a Zone change?? Otherwise, a small Hot house early on with that same deep mulch (1'+) should definitely do it. I would think?/!

Would there be any people with experiences to share?
Thank you

Here’s one example of a helpful guideline: check to see if there are other trees with similar chill hours in a similar micro-climate context.

Coincidentally, I actually have a Hale Haven Peach that is thriving 7’ from another S facing wall. Branches that grow within 2’ of the S wall die from the heat. That peach tree was planted before I knew about chill hours so this tree selection from a local nursery was mostly luck. I looked up the chill hours requirement for the peach and amazingly, that tree (like the Goldcot apricot) requires 800 chill hours. Given that the Hale Haven Peach was planted 7’ from the S wall, I will match that distance with the new bare-root apricot tree and, as the tree grows, prune any branches that grow closer than 2’ from the wall.

P.S. Demitrios, this guideline may or may not help you expand your zone possibilities and I hope someone else offers some ideas. However, there are many grape varieties that could serve as an edible vine option for a sunny location in zone 5b and higher.

Since it's such a tall wall with no way to harvest two stories up (except a ladder), I would like something that isn't going to be as heavy. Once the grapes start to come, with a good year, I just worry about the stress the weight would have on pulling the wall and grapes that grow inside the trellis. .
Those were my only major issues with using grapes.
I thank you for the reply.

Hi Amy, here is my anecdotal experience with apricot trees.  My parents live in the high desert too, but I think they are in Zone 5 or 6.  They have a free standing apricot tree somewhat close to their house (within 20 feet) in the south facing part of their property, but it almost never fruits because of early frosts.

Their neighbors a few blocks away on the same street also have a free standing apricot, planted a little closer to the house (more like 12 feet maybe), but on the north side of the house.  It almost always fruits despite the early frosts.

It's my understanding that it's the extreme temperature change when the sun hits the frosted blossom that kills off the flower;  when the flower can gradually warm up/defrost it's more likely to survive and produce fruit.  So my parents' tree frosts, gets the rising sun, loses the flowers.  The neighbors' tree frosts, warms up gradually in the shade, keeps the flowers.

I can't speak for your particular climate;  and mine doesn't have a hot enough summer for apricots so I have no direct experience, though I do have an almond against a south west facing wall that has been unexpectedly successful (it is a semi-dwarf Dutch cultivar, about 2-3 feet from a cinder block garage wall).  It typically flowers in February, though depending on how cold of a winter, has delayed till March before.  However, late hard frosts are generally not an issue in my area.