Arborvitae and hedge trimming in Washington and Oregon

Thuja hedges across the Northwest

Three plants called “cedar” or “arborvitae” make up most of the green walls between Northwest lots, and they behave differently under a trimmer.

• Emerald Green (Thuja occidentalis ‘Smaragd’). WSU’s screen-and-hedge guide lists it at 15 ft tall and 3 ft wide; OSU notes that unlike most of the species, which is susceptible to winter burn, ‘Smaragd’ does not discolor in winter. Planted in a tight row, it is the standard fence-line hedge from Vancouver to Bend.
• Other American arborvitae cultivars. The species grows to about 40 ft with a broad pyramid shape, and OSU describes it as often used for hedges. Older cultivars brown in winter and spread wider than Emerald Green, which is how a hedge from the 1990s ends up far deeper into the yard than anyone planned.
• Western redcedar (Thuja plicata). A forest tree listed at 50–70 ft, up to 200 ft in the wild. People hedge it, and it tolerates shearing while young, but a redcedar hedge planted tight to a property line is a row of trees with a 50-ft future. It is also the species losing crown to drought across the region (western redcedar dieback).

When to shear

For arborvitae and other non-flowering evergreen hedges, crews shear once the spring flush has hardened, in early summer, and take a lighter second pass in late summer so the hedge goes into winter tight; shearing in autumn leaves soft regrowth to be burned by the first frost. WSU’s rule for flowering hedges is to prune after the blooms drop: spring bloomers that flower on last year’s wood right after flowering, summer bloomers that flower on new wood in late winter. Photinia is the exception that proves the point: WSU’s leaf-spot guidance says to avoid summer pruning, because it pushes a flush of susceptible new growth; cut photinia in late winter instead.

For structural cuts on arborvitae, as opposed to surface shearing, the USDA Forest Service guide How to Prune Trees says conifers may be pruned any time of year, and that pruning in the dormant season keeps sap and resin flow from the cuts to a minimum (p. 16). Taking out a dead stem can happen whenever you notice it; the guide says dead branches can be removed any time (p. 17).

Two things that are normal and not a reason to call anyone: inner foliage on arborvitae turning brown in mid- to late summer is “cedar flagging,” older leaves being shed, and WSU says the dead material blows out with fall and winter winds; and a flush of pale new growth in May that darkens by July. Brown tips on the outside, or a whole plant going brown, are not flagging. The month-by-month calendar for trees and hedges is in the Pacific Northwest tree trimming calendar.

How hard you can cut

WSU’s EM089E puts the conifer rule in one sentence: take care not to cut into the interior dead zone of conifers, because they will not fill out with new green growth. Inside every arborvitae is a zone of bare brown stems; shear past the green and the hole is permanent. That has three consequences for an overgrown Thuja hedge:

• Width can only be taken back to the last green growth, usually a few inches, so a hedge that has grown 3 ft over the sidewalk cannot be put back without showing brown. Keizer’s code requires 8 ft of clearance over sidewalks and Auburn requires 7 ft, so an overgrown hedge over the sidewalk becomes a code issue as well as a hedge issue.
• Height can be reduced, because the top is cut across living stems; the cut tops look flat for a season or two and then the sides grow over them. Cut so the top is narrower than the base, which also sheds snow.
• A hedge with a dead side from a neighbor’s fence, a car exhaust or a disease is not recoverable by pruning; the usual answer is to replace the dead plants and accept a mismatch for a few years.

Broadleaf hedges are different. OSU lists English laurel (Prunus laurocerasus) at 10–20 ft, wide-spreading and vigorous, and notes that although it is often pruned as a hedge some say it is least suited to it; in practice that vigor means a laurel can be cut back to bare stems and will resprout, and that it needs two or three cuts a year to stay in bounds. Photinia regrows from hard cuts too, which is why renovation of both is a late-winter job, not a summer one.

The right tool for each cut

Shearing and pruning are different jobs, and the tool should match the cut:

• Hedge shears are for hedges only. The ISA’s young-tree brochure says so in as many words; a sheared ornamental tree or a sheared cedar meant to grow as a tree loses its natural form.
• Stems inside the hedge get a clean cut. The ISA recommends bypass (scissor-type) hand pruners over anvil pruners for cleaner cuts, and loppers or a pruning saw for anything over half an inch. The USDA guide sizes the tools: hand pruners for branches under 2.5 cm (about 1 in), lopping shears up to about 7 cm, small pruning saws up to about 10 cm (4 in), with bypass blades preferred to avoid crushing tissue (p. 18).
• Clean the blades when disease is in the hedge. If you are cutting out shoot-tip dieback or photinia leaf spot, the USDA guide’s method is to dip tools in 70 percent denatured alcohol or a 1-to-9 bleach solution for 1 to 2 minutes before each cut, then wash the bleach off with soap and water afterward because it corrodes metal (p. 20).
• Keep pole pruners away from the service drop. The same guide says pole pruners should not be used near utility lines except by qualified line-clearance crews (p. 19). A tall hedge under the wire to your house is a call to the utility first; most offer a free disconnect (see utility tree trimming).

Winter snow and ice splay

Wet Northwest snow and freezing rain pull multi-stemmed arborvitae apart; the January 2024 ice storm that triggered Portland’s emergency declaration left hedges splayed open across the metro. Stems that bend without breaking can be tied back upright with soft ties and will usually recover; stems that split at the base are removed. The pruning rule still applies: do not cut the bent stems short to tidy them, because the inside is bare. Tall, narrow cultivars and hedges sheared with a narrow top shed snow better.

Dieback that shows up after winter is often not winter damage. WSU’s diagnosis for arborvitae shoot-tip dieback is that it is usually cultural, not disease: poor drainage and waterlogged roots in winter, and poor air circulation. Its advice is to fix the drainage, water deeply but infrequently, give the plants spacing, and prune only to open the foliage and remove dead material; no chemical is recommended.

Laurel and photinia hedges

Laurel takes over Northwest hedgerows because it grows faster than anything else that is evergreen; the price is that it will reach 20 ft and a width to match, and it hedges into the neighbor’s yard as fast as yours. Expect to shear at least twice a year, and prefer a hedge trimmer on new growth to loppers on old wood, which leaves torn, browning leaves.

Photinia’s problem is leaf spot. WSU describes red-to-purple spots that develop gray centers and can defoliate the hedge, spread by splashing water on new growth, and notes that in western Washington a physiological leaf spot looks much the same. The management list is cultural: full sun, spacing and pruning for air movement, remove fallen leaves promptly, no overhead watering, and no summer pruning. A photinia hedge that is sheared in July and sprinkled from a lawn system will spot every year.

Fence-line hedges and neighbors

Most hedges sit on or near a property line, and the trimming questions are legal before they are horticultural. The baseline in both states: you may trim what overhangs your side, and you may not cut, injure or remove a plant rooted on the neighbor’s land. Oregon’s timber-trespass statute awards treble damages for willfully injuring or removing trees or shrubs on another’s land (ORS 105.810), and Washington’s does the same for cutting or injuring trees or shrubs without lawful authority (RCW 64.12.030). A hedge sheared to death from your side is an injury. The practical rules, including who pays when a hedge is on the line and how to handle a neighbor who wants it gone, are in Oregon neighbor tree law and Washington neighbor tree law.

Permits rarely apply to a hedge, because city tree codes start at a trunk diameter: 12 in in Portland, 6 in DSH in Seattle, 6 in DBH in Lake Oswego, Happy Valley and Milwaukie. An old arborvitae or laurel can pass 6 in at the base, so in those cities measure before removing a hedge; the thresholds are in tree removal permits in Oregon and tree removal permits in Washington.

What hedge trimming costs

We do not model a per-linear-foot price, because the same length of hedge takes an hour or two at head height and most of a day at twice that height with a ladder and clean-up. Hedge work is priced by crew-hour: our model uses $225 per crew-hour in Oregon and $210 in Washington for a three-person crew, built on the BLS May 2025 mean wage for tree trimmers ($35.40 Oregon, $32.20 Washington, a labor index). Modeled estimate, not quotes (method).

Modeled estimate, not quotes (method). A quote by the foot is fine if it also says the height and what happens to the clippings; haul-away is the hidden hour. Removing a hedge and grinding the stumps is priced as removal plus stump grinding at a modeled $4–$6 per inch of diameter, $150 minimum, on the stump grinding hub. The full trimming table is on the tree trimming cost page; back to the tree trimming hub.

Related guides

• Why arborvitae turn brown
• Emerald Green vs Green Giant arborvitae
• Best privacy trees for WA and OR yards