Key takeaways
- Cleaning: removes dead, dying, diseased, weakly attached or low-vigor branches.
- Thinning: reduces foliage density to let in light and air.
- Raising: removes lower branches to give clearance for people, vehicles and buildings.
- Reduction: reduces height or spread, cutting back to a branch large enough to take over.
- Topping and lion's tailing are listed as unacceptable practices in ANSI A300.
When an estimate says 'thin and raise the crown,' it helps to know what that means for your tree. These are the four standard terms arborists use, and the reasons to choose each one.
The four cuts
| Type | What is removed | Typical reason |
|---|---|---|
| Crown cleaning | Dead, dying, diseased, weakly attached or low-vigor branches | Reduce falling-branch risk and improve health |
| Crown thinning | Selected live branches to reduce density | Let in light and air; reduce wind and snow catch |
| Crown raising | Lower branches | Clearance over a walkway, driveway, roof or street |
| Crown reduction | Ends of branches, cut back to a branch large enough to take over | Reduce height or spread near a structure or line |
The ISA describes these in its consumer pruning guidance. Reduction keeps the form and structure of a tree far better than topping does, as long as the cut is made back to a secondary branch at least one-third the diameter of the stem being cut.
Why does crown cleaning come first?
On most jobs, cleaning is the baseline. Dead wood is a falling-branch problem in any wind, and in Northern Nevada we get strong downslope winds and heavy wet snow that find weak limbs. Our dead wooding guide goes deeper on this step.
Thinning is not stripping
Thinning means selecting branches to remove so that the remaining crown keeps its shape and its leaves. It is not the removal of most of the inner branches. ANSI A300, the American national standard for tree care operations, calls the removal of an excessive number of inner lateral branches lion's tailing and lists it as an unacceptable practice.
A thinned crown should still look like the species. If the tree ends up with bare inner branches and a tuft of leaves at the ends, too much came out.
Raising for clearance
Raising is for headroom: a sidewalk, a driveway, a roofline or a street. Remove the lowest branches and leave the crown intact. For young trees, lower branches also protect the trunk, and University of Nevada, Reno Extension says lower trunk branches shade young bark and can be taken off over three to five years as the tree matures.
What is the difference between crown reduction and topping?
Reduction is used when a tree has grown into a roof, wire or neighbor's yard and cannot be removed. The cuts are made back to branches that are large enough to carry on as the new end of the limb. Topping, by contrast, means cutting branches to stubs or to branches too small to take over. The ISA calls it perhaps the most harmful pruning practice known, and ANSI A300 defines it as heading cuts that shorten limbs back to a predetermined crown limit. Our guide on why topping is not pruning covers what it does to a tree.
Reduction has limits. A tree that is far too big for its space may be a removal candidate, and a certified arborist can tell you which it is.
Asking for the right work
When you request an estimate, describe the problem, not the cut: the branch hits the roof, or you cannot walk under it. The arborist then picks the type of pruning and writes it into your plan. Battle Born Tree Service has two ISA Certified Arborists on staff, including ISA Certified Arborist WE-11728A. Our tree trimming and pruning service covers all four, and a certified arborist assesses the job before work begins.
Sources
- International Society of Arboriculture, Trees Are Good: Pruning Your Trees (read October 17, 2026)
- Tree Care Industry Association: ANSI A300 Part 1, Pruning (read October 17, 2026)
- University of Nevada, Reno Extension: Planting Trees in Northern Nevada Landscapes (read October 17, 2026)