#2: Use The 1/3 and 1/4 Rules of Pruning

#1 - Don't Top Trees!
#2 - 1/3 and 1/4 Rules of Pruning
#3 - How to Make a Pruning Cut
#4 - The Value of Mulch
#5 - Where Roots Really Grow
#6 - Girdling Kills Trees
#7 - How to Plant a Containerized Tree
#8 - How to Plant a Bare-root Tree
#9 - Your Street Trees May Be City Trees

Never remove more than ¼ of a tree's crown in a season.

Where possible, try to encourage side branches that form angles that are ⅓ off vertical (10:00 or 2:00 positions).

For most species, the tree should have a single trunk.

Ideally, main side branches should be at least ⅓ smaller than the diameter of the trunk.

If removal of a main branch is necessary, cut it back to where it is attached to another large branch or the trunk. Do not truncate or leave a stub. See No.3 for how to make a pruning cut.

For most deciduous (broadleaf) trees, don't prune up from the bottom any more than ⅓ of the tree's total height.

“We envision a world
where trees and forests
are abundant, healthy,
and sustainable,
and highly valued
by all people.”