Emerald Green vs Green Giant arborvitae: size, spacing and Northwest fit
Emerald Green arborvitae grows 12–15 feet tall and 3–4 feet wide; Green Giant grows 40–60 feet tall and 12–18 feet wide, according to Oregon State University Extension. They are sold for the same job, but on a typical Washington or Oregon city lot only Emerald Green stays a hedge. Green Giant is a tree that needs room.
Emerald Green stays narrow; Green Giant becomes a tree. OSU Extension puts Emerald Green arborvitae at 12–15 ft tall and 3–4 ft wide, and Green Giant arborvitae at 40–60 ft tall and 12–18 ft wide. Green Giant can add 3–4 ft a year in optimal conditions (NC State); Emerald Green is rated slow. For a hedge on a Northwest city lot, choose Emerald Green.
Emerald Green vs Green Giant arborvitae: size and growth rate
The two plants share a pot size at the nursery and little else at maturity. OSU Extension’s hedge guide calls Emerald Green the most common hedge arborvitae in the Pacific Northwest and a good fit for small urban lots, and says Green Giant is best for larger spaces.
| Emerald Green (‘Smaragd’) | Green Giant | |
|---|---|---|
| What it is | Selection of eastern arborvitae, Thuja occidentalis | Hybrid, Thuja standishii × T. plicata (western redcedar) |
| Mature height | 12–15 ft (OSU); 8–20 ft (WSU); 15 ft (UConn) | 40–60 ft (OSU, NC State); to 60 ft (USNA) |
| Mature width | 3–4 ft (OSU); 3–5 ft (WSU); 5 ft (UConn) | 12–18 ft (OSU, NC State); 12–20 ft (USNA) |
| Growth rate | Species rated slow (NC State); no annual rate published by the sources checked | Rapid (USNA); 3–4 ft a year in optimal conditions (NC State); 30 ft at 30 years (USNA) |
| Cold hardiness | Zone 2 (WSU) | Zones 5–7 (USNA); 5a–8b (NC State) |
| Hedge spacing | 4 ft apart in rows (WSU); 3–4 ft for arborvitae (OSU) | No extension spacing figure found; see the spacing section |
| Root rot | Most susceptible to Phytophthora root rot (PNW Plant Disease Handbook) | Root rot can occur in poorly drained soils (NC State) |
| Deer | Its species is “a favorite food of deer” (UConn) | Resists deer (NC State) |
| Winter color | Typically keeps its color (OSU) | “Good winter color” (USNA) |
Sources: OSU Extension hedge guide (2021); WSU Extension EM089E (2015); UConn Plant Database; NC State Extension Plant Toolbox; U.S. National Arboretum (USNA) fact sheet (1999); PNW Plant Disease Management Handbook (rev. 2026). Checked 2026-10-02.
Growth rate is where they part fastest. The U.S. National Arboretum rates Green Giant rapid; NC State reports 3–4 feet a year in optimal conditions, and the University of Arkansas says young plants can put on 3–4 feet a year. The pace slows with age: the Arboretum’s figure of 30 feet at 30 years averages about 1 foot a year. None of the extension sources checked publishes an annual rate for Emerald Green; NC State rates its species, eastern arborvitae, slow.
What each one is: eastern arborvitae vs a western redcedar hybrid
Emerald Green is a selection of eastern arborvitae, Thuja occidentalis, a tree native from Nova Scotia west to Manitoba and south to Illinois, Tennessee and North Carolina. OSU’s Landscape Plants database lists it as ‘Smaragd’, also sold as ‘Emerald’ or ‘Emerald Green’, among the cultivars that hold their color in winter.
Green Giant is a hybrid of Japanese arborvitae (Thuja standishii) and western redcedar (Thuja plicata). The U.S. National Arboretum’s fact sheet records that a single plant came to the Arboretum in 1967 from D.T. Poulsen of Kvistgaard, Denmark. A University of Arkansas Extension profile dates the original find to 1937 and says DNA work in the mid-1990s identified it as a putative hybrid of the two species. It won a Pennsylvania Horticultural Society Gold Medal in 1998.
The western redcedar half matters here. The PNW Plant Disease Management Handbook rates western redcedar the most resistant arborvitae to Phytophthora root rot and ‘Smaragd’ the most susceptible. WSU’s Hortsense rates western redcedar highly resistant to cypress tip moth and eastern arborvitae very susceptible. Neither source rates Green Giant itself, so treat the parentage as a hint, not a guarantee. The native parent is profiled on western redcedar.
Green Giant and Emerald Green arborvitae spacing
OSU Extension’s hedge guide spaces arborvitae 3 to 4 feet apart, and WSU’s screens bulletin sets Emerald Green 4 feet apart in rows. That suits a plant that ends up 3–4 feet wide: the row closes into a hedge with little overlap.
No Northwest extension source checked gives a spacing for Green Giant. The numbers show the trade-off. A plant that ends up 12–18 feet wide, set 4 feet apart, overlaps each neighbor by 8–14 feet at maturity, which only works if you shear it as a hedge from the start; NC State notes that younger plants may be trimmed into hedges or screens. Set at its mature width, each one fills its own space but takes longer to close the gaps. OSU’s Amy Grotta lists overcrowding among the possible reasons an older arborvitae row declines.
| Spacing (ft) | Plants per 50 ft | Emerald Green at maturity | Green Giant at maturity |
|---|---|---|---|
| 3 | 17 | Touching to 1 ft overlap | 9–15 ft overlap |
| 4 | 13 | Up to 1 ft gap, or touching | 8–14 ft overlap |
| 6 | 9 | 2–3 ft gaps | 6–12 ft overlap |
| 8 | 7 | 4–5 ft gaps | 4–10 ft overlap |
| 12 | 5 | 8–9 ft gaps | Touching to 6 ft overlap |
Math: plants = 50 ÷ spacing, rounded up, spread evenly so the real spacing comes out slightly tighter. Overlap = mature width minus spacing, using OSU Extension’s widths (Emerald Green 3–4 ft, Green Giant 12–18 ft). Computed by Westcoast-Tree.org.
At 4 ft apart, mature Emerald Greens range from a 1 ft gap to touching; Green Giants overlap by 8–14 ft.
Count = length ÷ spacing, rounded up and spread evenly. Mature widths from OSU Extension: Emerald Green 3–4 ft, Green Giant 12–18 ft. Arithmetic, not a planting plan.
How each one handles a Northwest yard
Cold is not the problem. Every one of the 1,181 Washington and Oregon ZIP codes in USDA’s 2023 hardiness data is zone 5b or warmer, so none is colder than either plant’s rated limit (zone 2 for Emerald Green per WSU, zone 5 for Green Giant per USNA). USNA’s range for Green Giant stops at zone 7 and NC State’s at 8b; neither source addresses mild zone 9 gardens such as Seattle’s 98101. Zones by ZIP are in the hardiness zone guide. Water, soil, deer and snow decide the outcome.
- Summer drought: July and August bring 1.05 inches of rain at Portland, 1.57 at Sea-Tac and 0.64 at Salem (NOAA 1991–2020 normals). Retired OSU Extension horticulturist Neil Bell says even established arborvitae need water and advises soaking them every two to three weeks during dry spells. NC State says Green Giant resists periodic droughts.
- Heat: Portland hit 116°F and Seattle 108°F on June 28, 2021 (NOAA Climate.gov). OSU researchers found the scorch that followed in Northwest forests was worst on south- and west-facing slopes and exposed edges, and appeared within days or hours.
- Wet clay: many Willamette Valley soils are clay-heavy (OSU), and the PNW handbook says many arborvitae samples at the OSU Plant Clinic come from poorly drained, wet sites. ‘Smaragd’ is the most root-rot-susceptible arborvitae it rates; the USNA fact sheet says Green Giant grows in soils from sandy loam to heavy clay.
- Deer: OSU says deer usually feed on the bottom 4 to 5 feet of arborvitae. UConn calls eastern arborvitae a favorite deer food; NC State says Green Giant resists deer.
- Snow and ice: OSU advises tying up the tops where snow falls, notes freezing rain is worse than snow, and warns that limbs bent over stay bent. NC State lists stem breakage from ice and snow for eastern arborvitae. Splay repair is covered in arborvitae and hedge trimming.
- Coast: NC State says Green Giant does not tolerate salt spray or salty soils, a point for Astoria, Newport and other ocean-facing yards.
Drought shows up plant by plant: OSU notes that winter browning usually affects all the foliage, while drought stress appears sporadically on individual trees in a hedge. If one plant in the row is going brown, the diagnosis steps are in why arborvitae turn brown.
Power lines, fences and neighbors
Under distribution lines, PGE’s planting guide allows only small trees with a mature height of 20–30 feet; elsewhere in the yard it wants columnar or pyramidal trees at least 10 feet from wires, sidewalks and buildings. Emerald Green, at 12–15 feet, fits under the limit; Green Giant, at 40–60 feet, does not. Once branches near a line need cutting, that is the utility’s job: only utility or qualified line-clearance crews work within 10 feet of an energized line (WAC 296-45-035; OAR 437-002-0306). Utility-by-utility rules are under utility tree trimming.
Emerald Green on a fence line
- Mature width 3–4 ft (OSU)
- Trunk 1.5–2 ft off the line keeps branches on your side
- Fits under PGE’s 20–30 ft line limit
Green Giant on a fence line
- Mature width 12–18 ft (OSU)
- Trunk 6–9 ft off the line keeps branches on your side
- Planted 3 ft off the fence, it reaches 3–6 ft into the next yard
Setbacks are half the mature width, computed by Westcoast-Tree.org from OSU Extension’s figures.
Who may trim branches that cross the property line is covered on Washington neighbor tree law and Oregon neighbor tree law.
Trimming limits: neither one shrinks
OSU Extension’s guide is blunt: unlike laurel, arborvitae do not produce new growth if cut back to bare stems. Light pruning any time of year is fine; hard pruning is not. WSU’s bulletin says not to top Emerald Green, and a University of Arkansas Extension profile of Green Giant warns that an arborvitae hedge that outgrows its spot cannot be cut back like a broadleaf plant.
That makes the choice at planting permanent. Emerald Green can be held at hedge height with light shearing; a Green Giant meant to stay at 10 feet has to be sheared from youth, before it builds the bare interior that will not resprout. Why cutting the top off an overgrown tree is not the answer is covered in tree topping.
Topping won’t fix it. Ask a crew about removing every other plant or the whole row; OSU’s Amy Grotta notes crowded arborvitae may need thinning. Have the plant count and heights ready.
Call for a local estimate(877) 720-7431Better choices for small or dry yards
If neither fits, the wider list is in best privacy trees for Washington and Oregon. Three quick swaps:
- Dry, sunny east-side beds: ‘Medora’ Rocky Mountain juniper, a dense column of 10–15 by 5 feet that withstands drought (OSU Landscape Plants).
- Part shade or a holly look: tall Oregon grape, 8–10 feet and upright, or false holly, both low-water alternatives named by Washington’s weed board.
- Room and moist soil: western redcedar, the root-rot-resistant parent, though WSU links its dieback to warmer, drier summers, so plan on summer water.
Questions people ask
How tall does Emerald Green arborvitae get?
OSU Extension says 12–15 feet tall and 3–4 feet wide at maturity. WSU’s screens bulletin gives 8–20 feet, and UConn lists about 15 by 5 feet.
How fast does Emerald Green arborvitae grow?
Slowly. NC State rates eastern arborvitae, its species, slow, and none of the extension sources checked publishes an annual rate for the cultivar. Green Giant is the fast one, at 3–4 feet a year in optimal conditions.
How far apart should I plant Green Giant arborvitae?
No Northwest extension source gives a figure. OSU’s 3–4 feet is for arborvitae hedges in general; Green Giants that close will overlap by 8–14 feet at maturity unless sheared from the start, while spacing at their 12–18 foot mature width takes longer to fill.
Can you keep Green Giant arborvitae short?
Only by shearing it from a young age; NC State notes younger plants may be trimmed into hedges. Once it is overgrown, cutting into bare wood leaves holes that do not refill, and topping does not fix it.
Do deer eat Emerald Green arborvitae?
Yes. UConn calls eastern arborvitae a favorite deer food, and OSU says deer usually feed on the bottom 4 to 5 feet. NC State rates Green Giant as deer-resistant.
Sources
- OSU Extension, How to plant and care for arborvitae hedges in Oregon (Nov. 2021, reviewed 2025), checked 2026-10-02.
- WSU Extension EM089E, Selecting plants for screens and hedges (Brun and Dinius, 2015; copy hosted by Grant County PUD), checked 2026-10-02.
- U.S. National Arboretum, Thuja ‘Green Giant’ fact sheet (Nov. 1999), checked 2026-10-02.
- University of Arkansas Extension, Plant of the Week: Green Giant arborvitae (Jan. 2006), checked 2026-10-02.
- NC State Extension Gardener Plant Toolbox: Thuja ‘Green Giant’ and Thuja occidentalis, checked 2026-10-02.
- UConn Plant Database, Thuja occidentalis, checked 2026-10-02.
- OSU Landscape Plants database: Thuja occidentalis and Juniperus scopulorum, checked 2026-10-02.
- PNW Plant Disease Management Handbook, Arborvitae (Thuja occidentalis)-Root rot (rev. March 2026), checked 2026-10-02.
- WSU Hortsense, Arborvitae: Cypress tip moth, checked 2026-10-02.
- OSU Extension, Are my arborvitae goners? (Amy Grotta, 2018, reviewed 2024), checked 2026-10-02.
- OSU Extension, Understanding soil texture is key to better gardening, checked 2026-10-02.
- NOAA NCEI U.S. Climate Normals 1991–2020, monthly normals: Portland, Seattle-Tacoma, Salem, checked 2026-10-02.
- NOAA Climate.gov, Astounding heat obliterates all-time records across the Pacific Northwest (June 30, 2021), checked 2026-10-02.
- Oregon State University, Pacific Northwest heat dome tree damage more about temperature than drought (Feb. 3, 2023), checked 2026-10-02.
- USDA ARS Plant Hardiness Zone Map (2023), with ZIP data from PRISM Group, Oregon State University, checked 2026-10-02.
- Portland General Electric, Tree planting guide, checked 2026-10-02.
- WAC 296-45-035, line-clearance tree trimmer definition, checked 2026-10-02.
- Oregon OSHA Division 2/R, OAR 437-002-0306 (10-ft rule near lines), checked 2026-10-02.
- Washington State Noxious Weed Control Board, Tree and shrub alternatives for western Washington, checked 2026-10-02.
- WSU Forest Health, Western redcedar dieback briefing, checked 2026-10-02.
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