Western Red Cedar (Thuja plicata): The Fast, Deer-Resistant Privacy Screen for Zones 5–7
Western Red Cedar grows 2-3 ft a year, shrugs off deer, and outgrows every arborvitae rival — here’s how to plant and care for it in Zones 5-7.
Western red cedar (Thuja plicata) isn’t the arborvitae garden centers push hardest — that’s usually the ‘Green Giant’ hybrid — but if you want a genuine screening tree that grows fast, holds its color, and doesn’t get stripped by deer the first winter, the straight species deserves a second look. This guide covers where it actually thrives (the zone map undersells the nuance), how far apart to plant it, what the first two years of care look like, and the specific pests and diseases that show up on a Thuja plicata hedge — with the mechanism behind each one, not just a spray recommendation.
Why Western Red Cedar Beats Most Arborvitae for Screening
Two things set Thuja plicata apart from the rest of the arborvitae aisle: it’s fast without being a hybrid, and it’s the one deer are least likely to eat down to sticks. North Carolina State University’s Extension Gardener Plant Toolbox rates the species at a reliable 2 to 3 feet of growth per year [1] — no grafted hybrid vigor required, just the straight species performing as it does across its native Pacific Northwest range. That pace closes a modest planting gap within two or three seasons once the roots are established.
The deer-resistance part matters more than most buying guides admit. University of Illinois Extension states plainly that western red cedar is “less likely to be browsed by deer than other arborvitae” [3] — and unlike the vague “deer resistant” label slapped on half the nursery inventory, this one has a documented chemical reason behind it (more on that below). If you’re comparing screening options more broadly, our hedge plants growing guide covers the wider field; this one goes deep on the species most Pacific Northwest and Mid-Atlantic gardeners settle on anyway.
Where Western Red Cedar Thrives: Zones, Soil, and the Zone 8 Question
Plant it in USDA zones 5 through 7 without a second thought — that’s the range NC State Extension [1] and University of Illinois Extension [3] both document for the species, and it lines up with the RHS’s H6 hardiness rating for the UK, hardy throughout the country with no winter protection needed [2].
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Zone 8 is where the marketing gets ahead of the biology. Western red cedar is native to cool, consistently moist mixed-conifer forest running from coastal Alaska down to northwest California and inland through the Rockies to Montana [7] — a climate that rarely goes hot and dry at once. NC State is explicit that the species “does not tolerate drought or dry winds” [1]. That’s the real constraint at the warm edge of its range, not winter cold: maritime zone 8 — Pacific Northwest lowlands, or an irrigated coastal yard — works fine, while a hot, humid, or dry-summer zone 8 will stress the tree without consistent watering and some afternoon shade. If your zone 8 summers regularly hit 90°F with weeks between rain, budget for supplemental irrigation through at least the first three years, not just the establishment period.
On soil: it wants consistently moist, well-drained ground high in organic matter, pH 6.0 to 8.0 [1], and tolerates chalk, clay, loam, or sand [2] — texture matters less than moisture consistency. Full sun to partial shade both work, and it handles dappled light under a high canopy better than most conifers sold for screening [1][3].
Planting a Privacy Screen: Spacing and Timing
Spacing is a straight tradeoff between speed and plant cost, worth deciding on purpose rather than defaulting to whatever the nursery tag says. As a general guideline from hedging specialists working with the straight species, 60cm (2ft) spacing fills in fastest, 75cm (2ft 6in) is a reasonable middle ground, and 100cm (3ft) apart is the most economical option if you’re willing to wait an extra season or two for the gaps to close [8]. Tighter spacing costs more upfront but gets you the screen — and the privacy it’s for — noticeably sooner.
Plant in early spring or autumn, when the ground is workable but the tree isn’t fighting summer heat while its roots establish [1]. Water deeply and consistently through the first two growing seasons; this, not disease or pests, is the single most common reason a young cedar hedge fails. For material and depth guidance, our mulching guide covers the basics if you’re new to it — more on why mulch specifically matters for this species below. For layout options beyond a straight cedar row, see our privacy screen plants guide.
Care After Planting: Water, Mulch, and Pruning
In my experience walking overgrown or half-dead cedar hedges, the plants in trouble almost never trace back to bad soil — they trace back to nobody watering through the tree’s first two Augusts. Because western red cedar can’t tolerate drought or dry wind [1], deep watering during any dry stretch in years one and two isn’t optional maintenance; it’s the difference between a hedge that closes in three years and one that stalls or browns out.
Mulch does more here than most articles credit. A 2–3 inch layer keeps soil temperature and moisture more consistent, which matters specifically because this species evolved on a cool, damp forest floor, not open exposed ground [1][7]. Keep it a few inches clear of the trunk to avoid rot.
Pruning is genuinely optional for plant health — RHS confirms no pruning is required for the species to thrive [2] — but if you’re growing it as a formal or semi-formal hedge, trim in spring and again in late summer once it reaches your target height, tapering the sides slightly narrower at the top so lower branches still get light [2]. Skip that taper and the lower hedge thins out within a few years as upper growth shades it out.
Why Deer Usually Leave It Alone
This is the one thing almost no privacy-screen buying guide explains, and understanding it changes how you should read the “deer resistant” label generally. Western red cedar’s deer resistance isn’t behavioral — it’s chemical. A peer-reviewed study comparing browsing pressure tree-by-tree found heavily browsed western red cedars carried significantly lower total monoterpene concentrations (1.69% of dry needle weight) than lightly browsed trees (3.32%); one heavily browsed tree had no detectable monoterpenes at all [6]. Deer are choosing, tree by tree, based on how much aromatic defense compound — chiefly α-thujone — each individual carries.
That also means resistance in this species isn’t absolute; it’s genetic variation, not a species-wide shield. Some individual trees simply produce less of the deterrent chemistry and get browsed hard regardless of the species label. I’ve watched a newly planted hedge get stripped to bare stems in a single week when deer had no better forage nearby — resistance is relative to browsing pressure and to the individual plant’s chemistry, not a guarantee. The stakes are real enough that the USDA Forest Service funds an active breeding program at British Columbia’s Cowichan Lake Research Station selecting for higher-monoterpene stock, after estimating deer damage to planted seedlings costs the Pacific Northwest timber industry up to CAN$25 million a year [5]. Gardeners in high deer-pressure areas can pair a cedar screen with backup options from our deer-resistant plants guide if browsing becomes a problem.
Common Problems: A Diagnostic Table
Most western red cedar problems fall into one of two buckets: normal seasonal color change that panics new owners for no reason, or a specific, identifiable pest or pathogen. Here’s how to tell them apart before reaching for a spray.
| Symptom | Likely Cause | Fix |
|---|---|---|
| Foliage turns bronze, copper, or purple in winter but stays supple | Normal winter bronzing — the plant shifts pigment production to protect foliage from cold and winter sun | Leave it alone; green returns with spring growth |
| Interior needles (not tips) brown and drop in fall | Normal seasonal shedding of older foliage | No action needed; rake up the drop |
| Branch tips brown, with spindle-shaped bags of silk and debris hanging on them | Bagworm caterpillars feeding from inside their bag | Hand-pick bags October through April before eggs hatch; treat young larvae with Bt in June [1][3] |
| Individual shoot tips turn brown or straw-colored; tunnels visible if you peel one open | Arborvitae leafminer (Argyresthia cupressella) mining inside the foliage | Prune and destroy mined tips before adults emerge in June; avoid over-fertilizing with nitrogen [1][3] |
| Gray-brown fuzzy growth on new shoots in cool, wet spring weather | Gray mold (Botrytis cinerea), favored by poor airflow | Thin dense growth, avoid overhead watering, remove infected tips [3] |
| Shaded interior foliage turns reddish-brown and drops branch by branch, worst on young plants | Cedar leaf blight (Didymascella thujina), favored by dense shade and prolonged foliage moisture | Improve airflow and spacing; avoid overhead irrigation; resistant genetic stock exists but isn’t yet widely sold [4] |
| Whole plant wilts despite wet soil; roots are dark and mushy when checked | Phytophthora root rot from poor drainage | Improve drainage before replanting — T. plicata is comparatively resistant among Thuja species, but not immune [2] |
| Needling yellowing or browning starting near a road, driveway, or path treated with deicer | Salt spray or soil-borne salt damage; the species is salt-intolerant | Rinse foliage after exposure, install a burlap windbreak facing the road, avoid planting inside the splash zone [3] |
Frequently Asked Questions
Can you grow western red cedar in zone 8?
Only reliably in cooler, consistently moist zone 8 pockets, such as Pacific Northwest coastal areas. Inland or humid zone 8 summers push past what this species tolerates without irrigation and afternoon shade [1][7].
How far apart should you plant it for a privacy screen?
2ft (60cm) apart gives the fastest fill; 3ft (90–100cm) apart is more economical but takes longer to close [8].
Is western red cedar toxic to dogs or cats?
It doesn’t appear on the ASPCA’s toxic plant list for cats [9], but RHS notes the foliage is harmful if eaten and a skin allergen for people handling it [2] — treat it as low-risk, not risk-free, and keep an eye on pets that chew conifer foliage.
Does trimming it as a hedge slow its growth or hurt it?
No. RHS confirms the species needs no pruning to stay healthy — trimming is purely for shape. Two trims a year, spring and late summer, once it reaches your target height keeps a hedge dense instead of leggy [2].
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→ View My Garden CalendarKey Takeaway
Western red cedar rewards patience with soil and water in years one and two, then mostly takes care of itself — 2 to 3 feet of dense, comparatively deer-resistant growth a year, in the right zone and moisture, without a hybrid’s unpredictability. Get the site right, water it through its first two summers, and skip the zone 8 gamble unless you’re prepared to irrigate through a hot one.
Sources
- NC State Extension Gardener Plant Toolbox — Thuja plicata
- RHS — Thuja plicata
- University of Illinois Extension Web Tree Selector — Western Redcedar
- Chhetri et al., cedar leaf blight resistance mechanisms in western redcedar — PMC
- USDA Forest Service — Deployment of deer-resistant western redcedar
- Vourc’h et al., linking deer browsing and terpene production in Thuja plicata — PubMed
- Gymnosperm Database — Thuja plicata
- Evergreen Hedging — Thuja plicata planting spacing
- ASPCA — Toxic and Non-Toxic Plant List, Cats
