“Just trim it up” is one of the most common requests we hear, and one of the least helpful for the tree. Under TCIA-administered ANSI A300 Part 1, the national pruning standard, good pruning starts with a question: what are we trying to accomplish? At Bob Ray Company, our ISA Certified Arborists answer that question before they make a single cut. Here is how pruning objectives and pruning types work, and how they show up on your estimate.
Why Pruning Objectives Come First
Every pruning cut is a wound. Trees cannot heal the way people do; they seal off damaged wood and grow new tissue over the wound. Removing live branches also removes leaves, which produce the energy a tree needs to grow, defend itself, and store reserves for winter. Because pruning has a cost to the tree, A300 therefore requires arborists to prune for a reason.
Common objectives include:
- Reducing the likelihood of branch failure over a house, driveway, or play area
- Providing clearance for buildings, roofs, sidewalks, streets, signs, or lights
- Removing dead, diseased, or broken branches
- Improving structure, especially in younger trees
- Managing size or shape in limited space
- Improving views or light while keeping the tree healthy
Matching Pruning Types to Pruning Objectives
After setting the objective, the arborist selects one or more A300 pruning types:
- Cleaning: selective removal of dead, diseased, broken, or weakly attached branches. This is the most common type on mature trees.
- Thinning: selective removal of small live branches to reduce density, lower wind load, or let in light, while keeping the tree’s natural form.
- Raising: removing lower branches to provide vertical clearance over lawns, sidewalks, streets, and structures.
- Reduction: decreasing the height or spread of a tree or individual limbs using reduction cuts back to lateral branches.
A300 also recognizes structural pruning (developing a dominant leader and good branch spacing), restoration (improving trees damaged by storms, vandalism, or previous poor pruning), and vista pruning (opening a specific view). You can see structural pruning in action in our post on young tree training.
Putting Pruning Objectives in the Specification
A good estimate is more than “trim tree, $X.” Following A300, a pruning specification should describe:
- The pruning objectives and the pruning type
- Which part of the tree is being pruned (whole crown, one side, a specific limb)
- The size range of branches to be removed, for example “dead branches 1 inch in diameter and larger”
- The amount of live foliage to be removed, when relevant
- Clearance distances for raising or reduction work
Specific language protects you and the tree. It lets you compare estimates fairly and ensures the crew knows exactly what to do. It also prevents over-pruning, which is one of the most common forms of damage we see.
Pro tip: When comparing estimates, look for the pruning type and branch sizes in writing. If one quote says “crown clean, dead wood 1 inch and larger” and another just says “trim,” you are not comparing the same job.
How Much Is Enough?
Older rules of thumb, such as “never remove more than a quarter of the canopy,” are still useful warnings, but A300 does not rely on a single percentage. The right amount depends on the species, age, health, and the objective. A mature or stressed tree tolerates far less live branch removal than a young, vigorous one. Our earlier post on how much to prune covers this in more detail, and how often to trim explains pruning cycles.
Timing Matters Too
Arborists can do most routine pruning year-round, and dormant-season pruning in late fall and winter has advantages: branch structure is easy to see with the leaves off, and many insects and diseases are inactive. Some species have timing concerns. For example, in areas where oak wilt is present, it is best to prune oaks outside the spring and early summer period, when the beetles that spread the disease are active. Your arborist will factor this into the schedule.
Our Approach to Pruning Objectives
At Bob Ray Company, an ISA Certified Arborist walks the property with you, listens to your goals, and translates them into clear pruning objectives and an A300-based specification. We explain why we are removing each branch category and what we recommend leaving alone. Many clients are surprised to learn that the right answer is sometimes less pruning, not more. When a tree has defects that pruning alone cannot address, we may also recommend cabling and bracing or plant health care.
Frequently Asked Questions
What is the most common pruning type for mature trees?
Crown cleaning, which removes dead, diseased, broken, and weakly attached branches, is the most common and often the most beneficial type for mature trees.
Does thinning a tree make it safer in storms?
Selective thinning can reduce wind load, but over-thinning or removing interior branches (lion’s tailing) can actually make limbs more likely to fail. Therefore, arborists must thin carefully.
Can I combine pruning types?
Yes. Many jobs combine types, for example cleaning the whole crown and raising the lower branches over a driveway.
Schedule Pruning (Trimming) in Louisville
Bob Ray Company offers residential, commercial, and municipal tree pruning (trimming), plant health care, cabling and bracing, storm cleanup, and related tree care throughout Louisville and surrounding Kentucky and Indiana communities.
Call (502) 425-7654 or request a free estimate at BobRayCo.com.
No job too small, no tree too tall.
