There’s a lot of emphasis placed on making major pruning cuts when the trees are dormant and then very little said about summer pruning, limb bending, notching, etc. It’s hard to find consistent information on some of these techniques so I wanted to put them all down here and maybe get a discussion going on peoples experience with them.
I will update this post periodically as I experiment with some of these techniques and observe their results.
Used to control the size of a tree, extensively used in Backyard Orchard Culture. Since it can encourage the development of strong upright shoots, its best to do summer pruning around the summer solstice or when 2/3rd of the branch tips have fully set. Light summer pruning can be done at any time to prevent the formation of unwanted branches. Heading cuts are not advised with early summer pruning because it creates a lot of bushy branching at the tips of the cut branch (though they can still be used if you follow-up on removing the unwanted growth 2-4 weeks later).
A form of summer pruning (as a heading cut) that is said to redirect resources from the continued growth of branches and new leaves to fruit formation and earlier ripening, can also be used to encourage branching. Used early in the season to promote branching into a more productive / bushier form (ex. on flowers & peppers) or later in the season to encourage earlier ripening of fruit (ex. on figs grown in colder climates).
Using something to spread younger limbs and reduce their vertical orientation. A scaffold limb spread to a wider angle will have better balance between vegetative growth and fruit production. (more info needed )
In addition to the basic technique of limb spreading to get a good angle, there is the advanced technique of intentionally bending the limb so it’s growing tip is at or below horizontal reducing its apical dominance and growth rate and encouraging earlier fruiting (depending on the time of the year the limb bending was done (more info needed )). Could be a good alternative to completely pruning out a competing central leader or as a way to slow growth of specific branches during summer time without having to remove them completely. It could be used to “turn” the direction of branches; e.g. curving a young scaffold branch pointing in the north direction into a west / north-west direction. Limb bending to encourage fruiting should be done around the summer solstice (source).
Bending older limbs with hinge cuts
Using a hacksaw blade or file to cut the phloem just below the bark surface making a 1" wide (or 1/3rd way around the branch) notch below or above a bud. When applied above a bud it can encourage a shoot to form by cutting off the flow of growth regulator hormones. When applied below a bud it can encourage the production of a flower by sending the flow of carbohydrates from the leaves to the bud instead of the rest of the tree. Once the wound callouses the effect is gone.
- How many of you use the “notching” technique to encourage fruiting
- Notching Techniques Increase Branching of Young Apple Trees.pdf (53.8 KB)
- Young apple pruning question - #31 by applenut
Administering hormones in specific ways to coerce trees to branch in very specific ways, can be used in combination with notching.
- 6-Benzylaminopurine (6-BAP): used as a mix of 2% BAP Powder with 98% Lanolin, promotes branch formation, more here.
- Indole Acetic Acid: (more info needed )
- Gibberellic Acid (GA3): (more info needed )
Partial girdling (spiral girdle)
An alternative to making a pruning / heading cut, used to redirect resources from the continued growth of the branches above the girdle and to encourage branching below the girdle. Also used to encourage fruiting above the girdle. Using a hacksaw blade or file, cut the phloem just below the bark surface in a spiral pattern leaving a small section of bark connected. Once the wound callouses the effect is gone.
Size of connecting section and width of girdle depend on the size of the branch. For a 1/2" - 3/4" thick branch I use a hacksaw and leave a 1/4"-1/2" gap.
If you want to just slightly reduce the vigor of a specific 1 yr old branch using your pruning sheers and slicing a complete ring around the branch without removing any bark might be effective - but this needs more testing.
(more info needed )
[Update 01-14-2019]: Added info on hinge cuts, cleaned up text to remove ambiguity.
[Update 04-22-2021]: Made limb spreading its own section, cleaned up text to remove ambiguity.