Tree trimming and pruning in Washington and Oregon

The four pruning types, in plain words

Every legitimate pruning job is one of four things, and a written quote should name which. The ISA’s definitions, which follow the ANSI A300 pruning standard used in US arboriculture, are these [1]:

• Cleaning removes dead, dying, diseased, weakly attached and low-vigor branches. It is the job most Portland and Seattle yards need and the hardest to overdo.
• Thinning (reducing density) takes out selected live branches to let wind and light through the crown. On a bigleaf maple over a roof it reduces sail; it is not stripping the interior and leaving tufts at the ends.
• Raising removes lower branches for clearance over a roof, driveway, sidewalk or street. Several cities set the heights: Keizer requires 13 ft over the street and 8 ft over the sidewalk, Klamath Falls 13 ft and 7 ft, and Auburn 7 ft over sidewalks [2].
• Reduction shortens the tree or a limb by cutting back to a lateral branch at least one-third the diameter of the stem being removed [1]. That lateral keeps the limb alive and growing in a direction you chose, which is the difference between reduction and topping.

Get the type, the percentage of live crown to be removed, and the largest cut diameter in writing. The crown thinning and reduction page shows what each looks like on Northwest species. Tree trimming vs pruning covers what a quote should say and how often each kind of tree needs work, and bad tree trimming shows eight signs a job went wrong.

How much to cut: the USDA Forest Service numbers

The USDA Forest Service’s homeowner guide How to Prune Trees (NA-FR-01-95, revised 2012) turns “don’t overdo it” into numbers you can hold a quote against [36]:

• One-quarter of the live crown, at most, at one time. If more has to come out, spread it over successive years (pp. 5 and 22). It is the same line Portland drew in code as “excessive pruning.”
• Keep live branches on at least two-thirds of the tree’s height after raising the crown (pp. 7 and 22). On a 40-ft tree that means live limbs on roughly the top 27 ft; stripping more of the trunk to clear a roof or view weakens the stem.
• Cut size guide: branches under 5 cm (about 2 in), go ahead; 5 to 10 cm (2 to 4 in), think twice; over 10 cm (4 in), have a good reason (pp. 21–22). Seattle’s rules land on similar breakpoints: 2 in for major pruning of a street tree, 4 in for live branches on regulated private trees [28][29].
• Heavy limbs get three cuts: a shallow undercut outside the branch collar, a second cut farther out that drops the limb, then the final cut just outside the branch bark ridge and collar (p. 12). Flush cuts and long stubs both slow wound closure and invite decay (p. 14).
• No wound paint in most cases; the guide says dressings can slow closure and only help on oaks and elms wounded in their critical season (pp. 20–21).

The same guide says pole pruners should not be used near utility lines except by qualified line-clearance crews (p. 19), which is the homeowner version of the 10-ft rule below.

Why topping is damaging, and where it is banned

Topping is cutting branches back to stubs or to a height picked in advance, with no regard to where the laterals are. The ISA calls it perhaps the most harmful pruning practice known [1]. Its brochure lists the mechanics: the cuts remove 50 to 100 percent of the leaf area and starve the tree; shaded bark is suddenly in full sun and cankers; the stubs cannot close and decay moves down the branch; and the tree answers with weakly attached sprouts that can grow up to 20 ft a year and break in wind or ice [3]. A topped tree is more hazardous than it was, not less.

WSU Extension’s Linda Chalker-Scott makes the same case for Washington yards: after topping, epicormic shoots develop into weakly attached branches with an increasing potential to fall, so the tree becomes high-maintenance and potentially hazardous. Her advice is reduction cuts to a lateral and planting with mature size in mind [4].

Portland wrote this into code. PCC 11.60.040 says no tree may be “excessively pruned or topped” as defined in Title 11 [5]. The definitions in 11.80.020 call topping “the inappropriate pruning practice used to reduce tree height by cutting to a predetermined crown limit,” define excessive pruning as removing one-fourth or more of the functioning leaf, stem or root area in a single growing season, and treat topping as removal [6]. A topped 14-in maple in a Portland yard is therefore an unpermitted removal, and a topped street tree is both that and a violation of the street-tree permit rule.

Other cities draw similar lines. Salem defines removal to include topping or taking 30 percent or more of the crown, so topping a significant tree there needs a removal permit [7]. Kirkland counts topping that takes more than 25 percent of the live crown as removal and calls any pruning over 25 percent an unacceptable practice, and Issaquah requires a permit for pruning more than a quarter of the leaf or stem area in 12 months [8][9]. Canby and Mount Vernon prohibit topping street trees outright, and Newberg and Keizer require city permission before any right-of-way tree is topped or severely pruned [10][2].

When to prune in the Northwest

The ISA’s general rule is that light pruning to remove dead, weak or diseased wood can be done any time, growth and wound closure are maximized when cuts are made before the spring growth flush, and heavy pruning of live wood right after the flush should be avoided [1]. For most deciduous shade trees in the Willamette Valley and Puget Sound that means the dormant window from leaf drop to bud break.

Species and disease rules move the date:

• Fruit trees. The OSU, WSU and University of Idaho home-orchard guide says to prune once the danger of fall or early-winter freeze has passed but before growth starts in spring, and OSU calls yearly dormant-season pruning essential [11][12]. Sweet cherries are the exception: prune them in August, when there is less risk of bacterial canker entering the cuts [11].
• Elms in Portland. Pruning any elm between April 15 and October 15 is prohibited under the city’s Dutch elm disease rule, and pruned elm wood must be disposed of promptly [13].
• Birches. OSU Extension says not to prune birches during the few weeks in summer when bronze birch borer adults are flying, because pruning stress attracts egg-laying beetles; the exact weeks vary by location and spring weather, so dormant-season pruning is the safe default [14].
• Maples. Bigleaf, vine and Japanese maples cut in late winter bleed sap as it starts to rise. The bleeding is unsightly rather than harmful; if it bothers you, wait until the tree is in full leaf and prune lightly.
• Spring-flowering trees. Flowering cherry, plum, dogwood and magnolia set next year’s buds in summer. Prune them right after bloom or you remove next spring’s flowers.

Storm season is the other calendar. Washington DNR’s urban forestry program notes that the fall-to-winter transition brings increased windstorm potential, which is the argument for getting cleaning and weight reduction done in late summer or early fall [15].

Power lines: who trims what, and who pays

The wire decides the answer. Utilities trim their own primary and distribution lines on a cycle and at no charge to you; the service drop from the pole to your house is, at most utilities, your responsibility, and the utility will disconnect it so your arborist can work. No one but a qualified line-clearance tree trimmer may work within 10 ft of a line energized at up to 50 kV, under Oregon OSHA rule OAR 437-002-0306 and Washington’s WAC 296-24-960 [16][17].

So the utility pays for its lines, and you pay for the drop and for everything outside the utility’s clearance zone, including a tree the utility pruned on one side that now needs balancing. Oregon adds a duty to notify the utility before any work within 10 ft of a line over 600 volts (ORS 757.805) [26]. Telephone and cable lines belong to their own companies, and a branch resting on one is their call to make.

Pruning permits: Portland, Seattle and other cities

Pruning a tree on your own lot rarely needs a permit. Pruning a street tree, the one in the planting strip between sidewalk and curb, almost always does.

Portland. Any person pruning, removing or doing any other work on a street tree or City tree must first obtain a Type A tree permit (PCC 11.60.060), with an exception only for sucker shoots under half an inch [13][27]. Street-tree applications have been free since July 1, 2025 [27]. On private property the 25 percent rule applies: under a quarter of the crown needs no permit; more is treated as removal of a regulated tree [6].

Seattle. An SDOT permit is required to prune or remove any tree in the right-of-way, and major pruning, meaning branches 2 in and larger or 15 percent or more of the foliage, must be done by a registered Tree Service Provider [28]. On private lots, paid pruning of live branches 4 in and larger on any Tier 1 to 4 tree (6 in DSH and up) also has to be done by an SDCI-registered provider, who posts online notice 3 full business days before the work [29].

City-by-city removal and street-tree rules, including who issues the permit, are in tree removal permits in Oregon and tree removal permits in Washington.

What trimming costs

Pruning is priced by crew time, and crew time follows the size of the tree and how much of it is over something fragile. The modeled ranges below use the BLS May 2025 mean wage, $35.40 an hour in Oregon and $32.20 in Washington [35], grossed up for payroll burden, overhead and equipment to about $225 per crew-hour in Oregon and $210 in Washington. Modeled estimate, not quotes (method).

A climber working over a roof is slower than one over lawn, no truck access means brush dragged out by hand, and a Portland or Seattle street-tree job adds the permit step. The tree trimming cost page breaks the ranges down by job type and shows what separates a $400 cleaning from a $2,000 reduction.

Hedges, arborvitae and laurel

Sheared hedges are a different trade from crown pruning: the goal is a dense surface, the tool is a hedge trimmer, and the price follows linear feet and height rather than crew-hours in a canopy. Arborvitae, laurel, photinia and leyland cypress fill Northwest property lines, and the mistakes are the same on all of them: cutting back into bare interior wood that will not refill, and letting a hedge grow over the sidewalk until the city’s clearance rule applies. Keizer’s 8 ft over the sidewalk and Auburn’s 7 ft are typical [2]. Timing, height reduction and what to do with a hedge that has gone brown on one side are on arborvitae and hedge trimming.

Crown thinning and reduction on big trees

The request that most often turns into a topping job is “the fir is too tall.” The right answers are reduction to laterals, where the species allows it, and thinning to reduce sail; for a 100-ft Douglas fir the honest answer is often that neither will make it much shorter, and the real choice is between leaving it and removing it. Portland’s 25 percent limit per season [6] and the ISA’s one-third lateral rule [1] are the two numbers to hold a quote against. Species notes for maples, firs, cedars and oaks are on crown thinning and reduction. Pines, firs and other conifers need different cuts, covered in how to trim a pine tree; oak timing, mistletoe and city oak rules are in oak tree trimming.

Fruit trees

Home orchards in the Hood River valley, the Willamette Valley and the Yakima and Wenatchee valleys run on the same calendar: dormant pruning after the risk of a hard freeze has passed and before bud break, every year, and summer pruning only to slow a tree that is growing too fast [11][12]. Sweet cherries get their cut in August to keep bacterial canker out of the wounds [11]. Apples and pears on dwarfing rootstock stay small enough for a homeowner to prune from the ground; a neglected standard apple takes a crew and several years of staged cuts. Rootstocks, renovation and the timing table are on fruit tree pruning.

Tree trimming by area

Statewide rules, costs and storm seasons: Tree trimming in Washington · Tree trimming in Oregon.

• Tree trimming in Bend
• Tree trimming in Eugene
• Tree trimming in Gresham
• Tree trimming in Hillsboro
• Tree trimming in Portland
• Tree trimming in Salem
• Tree trimming in Bellevue
• Tree trimming in Seattle
• Tree trimming in Spokane
• Tree trimming in Tacoma
• Tree trimming in Vancouver

Related guides

• Tree trimming vs pruning: what a quote should say, and how often trees need it
• Bad tree trimming: 8 signs a tree was pruned wrong, and what to do now
• How to trim a pine tree and other Northwest conifers
• Oak tree trimming: when, how much, and what to leave alone
• How to prune a tree: proper cuts and the three-cut method
• Tree topping: why it fails and what to do instead
• How to prune a Japanese maple
• Why arborvitae turn brown