OK, I took a quick look at "spindle pruning", since Im not familiar with that term. IT seems to be a form of central leader training, with a bit of espalier training as well.

If my assumptions are right, apples, pears and apricots should be ok with this. I dont think peach would work, due to the large amount of pruning you need to do (just my take on it, if youre willing to train the peach that way, thats fine. Ive seen pics of some gorgeous espalier peaches!)

As for cherry and plums, I would think that sour cherries should be treated as peaches, as well as japanese plums. IF they are european plums I would guess that this style of pruning would be ok for it.

As for jujubes, pawpaws, a shipova, a mulberry, and a persimmon:

I dont know enough about Jujubes, shipova or mulberry to answer. I think mulberry do well on their own, as well as jujube, but thats from a long ago reading :P

As for pawpaw, I havent read much, if anything at all in regards to pruning them. They seem to grow just fine in their own, with a gorgeous natural conical shape. You may be able to trim away some branches to achieve some sort of central leader. There is little information in regards to "proper" orchard care of pawpaw, because it is relatively new, or atleast has a renewed interest.

As for persimmion, I believe ive read "open center" like peaches, but Ive never seen anything else.

A general rule is that most trees can be pruned to what ever shape, as long as you are willing to do the work that is entailed with some trees. Some trees lend themselves to central leader type prunings better then others (certain apples, cherries and even walnuts), while others have a large more open shape (stone fruits liek necterines, peaches, and plums).

For less work, id recommend learning the "typical" growth habit of your certain trees species and varieties, and use pruning methods that compliment these habits. This creates A LOT less work for you.

It sounds like we're attempting the same thing. I started last spring and now have over 50 trees, though ~20 are in containers. The apples are spaced at 5-6' and are doing well. A few of the trees are bearing this year. I'm most excited about the 9 apples on a Goldrush (G16). So far 5' spacing has been pretty good. I used some at 6 or 6.5' since it was a slightly more vigorous rootstock.

I planted peaches and pears this spring at 4' spacing. Most of the pears are on Quince rootstock, which should help keep them manageable (and for better preciosity). I'm not sure how easy it will be to keep the peaches in their designated space. They are growing pretty fast and look great. I've started branch bending with them, though I haven't heard much about it online.

I wouldn't go any closer than about 4'. Some professional orchards go much closer (2' or less for apples and sometimes even pears), but that feels like asking for trouble to me. It will also cost twice as much to buy all the trees. Even 4' will take some serious pruning. So far all I've had to cut off is branches which were growing far too close to the ground, but I can tell that more will be needed in another year or so, as some of the trees are getting to be almost as big as I want them. Hopefully I'll be able to make myself do so when needed. Tying things down has worked pretty well, but it is early yet and takes a bit of work.

Scott is years ahead of us in creating a high density backyard orchard, so he may have some additional thoughts on the different potential spacings. I know that he's already commented on Jujube (3-4' should work, 8' would be easier), apples (5-7'), and pears (1.75' is too tight, 2.5' should work with spindle pruning, 5' would be good).

What is the downside to high density - tall spindle planting of dwarf apples? Based on the umass research, seams like a great idea for homeowners who do not need a large volume of apples. The benefits I see are:

1. Space saving - grow more varieties in a smaller space.
2. Easy to manage and prune - no getting on ladders to prune or harvest.
3. Takes less pruning skill - videos say just tie down the branches the first year or two and remove larger branches in future years.

I am thinking of purchasing some dwarf apples on G-11 and G-30 this fall and attaching the trees to a metal 12 foot pole like shown on this video. Would like any thoughts from anyone who has tried this method.
http://www.youtube.com/watch?v=Bt3aiPbuTTY

Great web site on tall spindle method here:
www.umass.edu/fruitadvisor/clements/tallspindleapple/index.html

This is my second year growing apple trees on the tall spindle and so far they are doing well. The second year and they have grown allmost to 10 feet which is about where you start pruning to a side limb. All of my trees have about 7 to 10 apples on them. I wish I had done more of these then standard dwarf or semi dwarf.

Commercial easy production long rows, not so much for home growers I think.
That's all good if you're willing to put up the work every year, as we get older and apart this world I like to put some trees in which can still thrive without much care. I wouldn't want to know trees like this left alone for a couple of years.

Konrad, you make a very good point; one I had observed with my own grandparents but had forgotten. My grandfather had planted grape vines and then got too weak to tend them and they just went berserk. It took me days to clear out the mess of just 8 grape vines that had been left for probably a decade. I can't understand why I did not care for them for him; it would have made him so happy.

I will have to give this method some more thought. I can see my own little orchard being untended in the same manner. I just don't want to end up having a tree canopy either. I think I will try to graft peaches lower on their own trunk to see if I can find a happy medium between open-center and tall-spindle.

I Put my tall spindle in my vegetable garden. The space available was limited and I wanted some different apples. So it works for me in my garden. I have nine different types of apples in a space I couldn't plant one dwarf Because the area is to skinny for that.