North American Fruit Explorers mailing list at ibiblio

[Alan Haigh <alandhaigh@gmail.com>]

As far as I know the main advantage to maintaining a tree as a central
leader is that it makes more efficient use of light and allows greater
production per acre- this is what I've read in guides for commercial fruit
production.  This is not a significant advantage in the home orchard.

The advantage of open center is that if you keep branches from overlapping
it allows better penetration of light and circulation of air.

I believe that the easiest way to originally train all common fruit tree
species is to a central leader form.  Maybe for pears and apples you will
want to keep it this way (for the first 20 years, anyway) but eventually
for peaches and plums you will probably want to opt for an open center- at
least if you live where brown rot is a problem (the humid regions,
especially).  Even without the brown rot, peaches are easier managed to an
open center so light gets to the lower wood well and keeps generating new
wood.

With a central leader you can follow a simple training procedure of
removing only oversized branches- branches more than 1/3rd to 1/2 the
diameter of the trunk at the point of attachment to that trunk  and leave
all others.  When  the tree begins to fruit you can start to choose (or
completely choose) your permanent scaffold branches and in the case of
peaches, often cut out the center of the tree.

For peaches I will usually wait a couple years after they start bearing to
open the center because the center gives me something to tie sagging
branches to (peaches are heavy!) but you have to be careful not to allow
your permanent scaffolds to be excessively shaded, which means doing summer
pruning.  A beginner in particular might just want to cut the center out.
This would usually be the second or third year after planting if the peach
tree is growing well.  Same with J. plums but E plums take a couple years
more.

A central leader also makes the use of branch spreaders possible, which is
usually the best way to get branches at the desired angle.  However
maintaining a balanced central leader tree requires more skill than an open
center free standing tree because upper branches must eventually be cycled
out as their diameter becomes excessive and replaced with new ones.

If any of you who reads this would like to read a copy of an article I
wrote for Pomona a few years back about training and pruning to ratios,
just e-me a request.  I explain all of this much better and in more detail
in that article.