30 percent removal rule

Tackle big ol' trees at a pruning workshop and the question of how much tree can be removed inevitably comes up. My advice generally is to remove several large branches, stopping when as much of the 30% of the canopy is down on the ground.

Root systems can be shocked if too many of the leaves supporting those roots are no longer taking in sunlight in the immediate growing season ahead . . . so "they" say. A bigger part of the story relates to light penetration. Truly scalping a tree leads to a ton of sucker growth. You will get watersprouts where big limbs are removed, yes, but this is limited compared to a complete topping. Those watersprouts can be aggressively thinned in early August thus directing the tree back towards "calm" and a fruitful comeback.

Then you see trees cut back to practically stumps that survive. What's relevant here?

Lost Nation Orchard
Zone 4b in New Hampshire

Like your post, Michael. it helps to hear your synthesis of the various factors and also the mysteries.
Then the question is whether come August this person will get time to go after the water sprouts.
Why, btw, are they called water sprouts? During pruning time that question echoes in my brain....

Kevin Frank, zone 5b central nh

Now you have me examining my spelling of watersprout! Take out an 'r' and you have an intense columnar vortex (usually appearing as a funnel-shaped cloud) that occurs over a body of water. Apparently my inherent spelling springs from waterspout ... which in a sense reflects the energy of a water sprout in a fruit tree. Botanically speaking, this term relates to the term "epicormic":

Quote
Dave's Garden (website)
An epicormic sprout is a shoot that arises from latent or adventitious buds. Also known as a water sprout, they form on stems and branches, and suckers produced from the base of trees. In older wood, epicormic shoots can result from severe defoliation or radical pruning.

From the Greek epi, upon and kormos, a branchless tree trunk.

Pacing growth response in renovating an overgrown tree seems pivotal to me as regards the 30 percent rule. Year two is when serious thinning cuts come into play and these will trigger far less water sprout production. Allowing the weaker suckers another growing season to "settle" is part of this, and those in turn will have a chance to grow laterals in year two and form fruit buds by year three. Such young wood can be bent into a favorable position to fill a hole in the tree structure as well.

Lost Nation Orchard
Zone 4b in New Hampshire