Tree Trimming vs. Tree Pruning: What Your Trees Actually Need

Ask a homeowner what their tree needs and they will say a trim. Ask an arborist what they plan to do and they will say pruning. The two words get used as if they were interchangeable, and on a quote they often are, because crews tend to write down what the customer said. Underneath, they point at different work with different goals. This guide separates them, explains the standard terms in plain language, and shows what bad trimming actually costs you later.

What homeowners mean by trimming

To most homeowners, trimming means making a tree smaller or better shaped. It is the word used for hedges, for a ficus that has swallowed a walkway, for the ornamental by the front window that needs to look neat again. The goal is appearance and clearance: branches off the roof, off the sidewalk, out of the gutter. Trimming in this sense is real work, and for shrubs, hedges and small ornamentals it is the right word and the right job. The trouble starts when the same word, and the same thinking, gets applied to a large shade tree. A big tree is not a hedge. Cutting it for shape alone, without a structural goal, is how trees get ruined slowly.

What arborists mean by pruning

Pruning is the term the trade uses for work on trees, and it has a standard behind it: ANSI A300, the American National Standard for tree care operations. Under A300, pruning is never just cutting some off. Every pruning job is supposed to start with an objective, stated before anyone climbs: clear the roof, remove deadwood, fix a structural defect, reduce the load on one side. The cuts follow from the objective. That is why a good estimate names the objective in plain words. "Trim the oak" tells a crew almost nothing. "Remove the deadwood and clear the roof by six feet, taking no more live wood than needed" tells them exactly what the job is, and it can be checked when the work is done.

The A300 vocabulary in plain language

Three pruning types cover most of the work on valley properties.

Crown cleaning. Removing dead, dying, diseased and broken branches from the crown. This is the most common pruning there is, and the least risky. Deadwood comes out, live canopy stays.

Crown raising. Removing lower branches to give clearance underneath: over a sidewalk, a driveway, a roof edge or a patio. Raising is about what happens below the tree. It should be done gradually on young trees rather than all at once on a mature one.

Crown reduction. Shortening branches back to a live lateral branch large enough to take over, to reduce height or spread, or to take weight off a limb. Done properly, a reduction keeps the tree's natural shape at a smaller size. Done badly, it is topping, which is the next section.

One more A300 habit worth knowing: cuts are made at the branch collar, the raised ring where a branch meets the trunk or a larger limb. Cutting there lets the tree close the wound with its own tissue.

Bad trimming: topping, lion-tailing and flush cuts

Three practices account for most of the damage we get called out to fix.

Topping is cutting the top off a tree, or cutting large limbs back to stubs, to make the tree shorter fast. A topped tree responds with a flush of fast, weakly attached regrowth that shoots up from the stubs. Within a few years the tree is as tall as before, but the new wood is now attached to decaying stubs instead of solid structure. Topping also starves a tree, because removing most of the canopy removes most of its food supply. A topped tree is not a smaller tree. It is a damaged tree with a recurring bill attached.

Lion-tailing is stripping the inner and lower growth from a limb and leaving a tuft of foliage at the end, like a lion's tail. It is done to make a tree look cleaned out. What it actually does is move the limb's weight to its tip and remove the inner branches that absorb sway. Lion-tailed limbs break in wind at a much higher rate.

Flush cuts are cuts made flat against the trunk, removing the branch collar. The collar is where the tree's wound-sealing tissue lives. A flush cut removes it, and the wound can stay open to decay for years. The stub cut, its opposite, leaves a dead peg that rots back into the trunk. Both errors come from the same place: not knowing where the cut belongs.

Each of these mistakes costs more later than the job cost in the first place, because the follow-up work is hazard work on a weakened tree, or a removal that did not have to happen yet.

Which San Gabriel Valley trees need which approach

Oaks. Coast live oaks and valley oaks get pruning in the strict sense: light crown cleaning, small cuts, minimal live foliage removed. Our guide to when to trim oak trees covers the timing. An oak should never be topped, and heavy reductions on mature oaks cause more problems than they solve.

Palms. Palms get trimmed: dead fronds and seed pods off, on roughly an annual cycle. Palms are not pruned in the A300 sense, because a palm has one growing point and no branches to structure. Our palm care guide covers skinning and cycles.

Eucalyptus and other fast growers. Tall, fast species usually need reduction and cleaning on a regular cycle, done before limbs get heavy over roofs. The goal is managing weight and falling-limb risk, not shape.

Fruit trees. Fruit trees are pruned for production and structure, usually in winter for deciduous types. This is the one place where heavier, deliberate cutting is normal, because the objective is fruit, not shade.

Hedges, ficus and ornamentals. These get trimmed, and trimming is the right word. They are kept at a set size and shape by design, and they tolerate it because they are small, vigorous and cut often.

How to ask for the right work

When you call for an estimate, three things get you a better job. First, state the problem, not the procedure: "the limb over the roof worries me" leads to better work than "trim it back hard." Second, ask what the objective is and how much live foliage the work removes. A crew that thinks in A300 terms can answer both without hesitating. Third, remember that in some valley cities the amount removed is a legal question as well as a tree question. San Marino requires a permit for pruning that removes more than 10 percent of an oak, and La Cañada Flintridge requires approval for heavy work on protected oaks and sycamores. Our San Marino page summarizes estimates there, and our tree trimming and pruning page sets out how we scope the work. And when pruning is no longer the right answer because the defect is structural, our tree removal page explains the next step plainly, instead of selling you one more trim.

Pruning type definitions follow ANSI A300 (Part 1), the American National Standard for tree care operations, summarized here in plain language. Permit thresholds are covered in our protected trees guide and are checked again at your estimate.