How NOT to prune a tree 4: Oh No! Geometry!

Traditionally, we try to control the angle that branches grow on Fruit Trees.
60 degrees (2 or 10 o'clock) is considered the best angle.
Between 90 degrees (3 or 6 o'clock) and 45 degrees ("1:30" or "10:30") is okay/acceptable.
Between 30 degrees (1 or 11 o'clock) and 45 degrees should be retrained out to 45-60 degrees.
Less than 30 degrees is difficult to retrain without splitting, it should probably be removed down to a outward/downward facing bud at the base of the branch. The bud will start at a better angle than the original branch, and can be trained to a good angle.

The tree in the photo is prone to "underhangs": branches that leave the bottom side of a larger branch, and continue downward at less than 90 degrees. Since the tree is a Honey Locust, this isn't a problem. However, on a fruit tree, underhangs usually don't bear fruit. If the downward branch is small, remove it back to the main branch. If it is too late and it is already too large to prune, then prune the tip end back to a smaller upward facing branch.

More recent research has shown that branch angle isn't the only factor that determines the strength of the branch. Branches should be LESS than half the diameter of the trunk. Branches of this smaller diameter develop alternating layers of trunk and branch tissue where the two meet, making a stronger union. Larger branches that are OVER half the diameter of the trunk tend to develop a single continuous layer of tissue where the trunk and branch meet, which isn't as strong as the double alternating layers.

The branches of the tree in the photo were trained out to 45-60 degrees when the tree was young. However, the branch on the left is too large - the smaller branches on the right side are actually stronger.

The following is the source of my information, with illustrations of how the tree tissues develop where the branch meets the trunk:
http://www.cmg.colostate.edu/gardennotes/612.pdf

Oaks are known for their strength.
Notice the naturally strong branch pattern of the little oak in the photo.

Some trees naturally sprout branches in whorls around the trunk, as shown in the photo.
This is similar to the branching pattern we try to create in Dwarf and Semi-dwarf Fruit trees, however it isn't natural and requires training.

Too much of a good thing:
I did a good job of dwarfing this peach and starting a vase shape.
However, there is a problem as shown in the next photo.

A different look at branch angles:
This is a picture of the same little tree taken from above.
There are too many branches starting from too small an area. As the tree gets larger, some of the branches won't have enough room to develop a sturdy union with the trunk. This tree needs to have its branches thinned to allow for correct spacing when the tree is older.

This message was edited Mar 27, 2010 2:39 PM

This is a little pear tree. The branching pattern is very good for a pear. Pears tend to have too narrow too upright branch angles.

This is the same little pear tree from above.
It looks like it has a lot of branches, like the peach. But unlike the peach, because the branches are spaced wider vertically, they will have enough room horizontally.

Thank you for this lesson!

pollengarden enjoying your lesson too!
Cuckoo

Does this also apply to plum trees? Mine are still in 3 gallon pots and I need to plant them in the ground this weekend as well as prune..
Susie

Please don't prune your trees until the roots are established. See http://davesgarden.com/community/forums/t/1078633/
With potted trees, double check to make sure they aren't root-bound, I've seen more problems with it these past few years.
The angle of the branch, and the size ratio between branch and trunk, apply to any type of tree to improve strength.
It is hard to give exact instructions for Plums because the natural shape and growth pattern varies so much. A plum can be anything from a bush to a fairly large tree. The branch pattern can be slender, whippy, and peach-like - which lends itself to a vase shape. Or the branch pattern can be gnarled and twiggy and brittle - these are better pruned as a modified leader.
For anyone who doesn't want to wait until I get around to adding more photos: Check out several books on pruning from your library. Consult and compare all of them before each type of tree. Then buy the one you found most useful. Some pruning books are better at Fruit trees than others, some are better at young trees, some are better with old trees.

Pollengarden, I am very dense at this stuff... I have been trying to learn from your episodes but I am having trouble.. I may have already destroyed some of them. Can I upload pics or videos of my trees and you tell me how to snip them correctly??? Please!

Well - I will warn you that I have learned from my mistakes, and I'm still making mistakes and learning from them. First question: How old are the trees and how much new growth have they put on over the past 3 years? It should be increasing each year if they were planted in the last 3-5 years, it shouldn't be decreasing if they are established trees. See my post on "Remember your Roots"

If your trees are established and healthy, and you didn't make any cuts larger that a quarter coin, and you didn't take off more than a third of the growth - then you didn't destroy your trees. (Hint: they're a plant - they grow back!) But your caution is good - when it doubt, leave the pruners in the tool box. Go ahead and post a picture(s) of ONE tree, and I'll give you my opinion, for what it is worth.

I have some peach trees that are old enough to prune that I intend to use as examples - but it is already getting to late here to prune - it will definitely be another lesson in how NOT to prune a tree.

OK my trees are not 3 years yet so I will force myself to wait. I'll check back next year if we're still around ok. Thanks~

If the roots aren't established enough to prune the branches, you can still use spreaders. Be gentle and work in increments - if you try and force a branch too far too soon it will split.