Branch collar
Also called: collar cut, branch bark ridge, flush cut, stub cut, where to cut a branch, pruning cut
The swollen ring of trunk tissue at the base of a branch, where it joins the trunk or a larger limb. A pruning cut goes just outside it — not flush with the trunk, which removes the collar, and not leaving a stub past it — because the collar holds the cells that grow over and seal the wound.
Look at where any branch meets the trunk and there’s a slight bulge around its base, often with a raised line of bark running up and over the top of the junction. The bulge is the collar: trunk wood that grows around the branch base each year, and the tissue the tree uses to wall off a lost branch and close the wound. The line on top is the branch bark ridge. Together they mark the target for every pruning cut: start just outside the ridge, angle the cut down and slightly away from the trunk, and finish just outside the collar. The result is a small oval wound that the tree begins closing the first season and covers in one to three years on a healthy tree.
The two wrong cuts are common enough to have names. A flush cut takes the branch off even with the trunk, which removes the collar and its defensive tissue, leaves a larger wound, and opens the trunk itself to decay that can run down the stem for years. A stub cut leaves several inches of branch past the collar; the stub dies, the tree can’t close over it, and decay enters through it — this is also what topping produces along every cut. On a limb thicker than about 2 inches, the collar cut is the third of three cuts: an undercut and a top cut a foot out remove the weight first so the final cut at the collar doesn’t tear bark down the trunk.
It’s the single technique that separates pruning from cutting, and it’s the first thing to check on a finished job, yours or a crew’s — the hiring guide has it on the walk-through and the DIY guide makes it the rule.