Tree · Cupressaceae
Emerald Green Arborvitae
Thuja occidentalis
Set it where you want privacy and a calm green backdrop, mind the deer and the snow, and it frames a property for decades.
Full sun
Every 5–10 days
USDA 3–7
12–14 ft · 3.7–4.3 m
Overview
Emerald Green Arborvitae is the evergreen that quietly defines the edges of a property, the soft green wall that turns an open yard into a room of its own. A 'Smaragd' selection of the eastern white cedar, Thuja occidentalis, it carries a slender, upright presence and a steady green that reads the same in January as in June. At a mature 12 to 14 feet (3.7 to 4.3 m) tall and a slim 3 to 4 feet (91 to 122 cm) wide, it draws a clean vertical line without crowding the spaces it borders.
Its appeal is its restraint. Growth is unhurried, the upkeep light, and the look it lends a garden is composed rather than busy, a backdrop that flatters whatever is planted in front of it. It settles into northern gardens where little else stays green, untroubled by cold to -40°F (-40°C) and forgiving of most soils, provided the ground drains. Drought and a waterlogged bed are the two settings it will not abide.
The considerations are seasonal and worth planning around before a single plant goes in. Deer favor it, deep snow can splay a multi-stem specimen, and an exposed, windy corner dulls the foliage to brown. Choose the placement with care and prepare it for winter, and what follows is effortless structure for years, a living architecture that asks almost nothing in return.
Care
The short version: a bright, sunny position, soil held evenly damp without ever sitting wet, and a generous watering each fall before frost locks the ground. Screen it from winter wind and browsing deer, and bind multi-stem specimens together before the snow season arrives.
Light
It looks its fullest and stays its healthiest in full sun, the setting that keeps a screen dense and unbroken, though it accepts partial shade without complaint. Where the light falls thin, the form opens and the clean green wall loses its composure.
Water
Keep the soil consistently moist and well drained, watering deeply every 5 to 10 days through dry spells to hold its even color. It has no patience for drought or a dry, windy exposure, so give it a thorough soak in fall before the ground freezes, the step that carries its look intact through winter.
Soil
It settles into moist, fertile, well-drained loam and even makes peace with clay, as long as water moves through rather than lingers. The pH range is generous, from 6.0 to 8.0, so most garden ground from slightly acidic to alkaline will serve a planting well.
Temperature
Cold poses no obstacle to the role it plays. Holding from -40°F to 100°F (-40°C to 38°C), it keeps a garden framed in green even where winters are at their hardest.
Humidity
Ordinary outdoor humidity suits it, so there is nothing to monitor on that front. Airflow and steady soil moisture do far more for its appearance than the dampness of the air ever will.
Feeding
A single feeding in spring with a balanced, slow-release evergreen fertilizer is all the routine it needs. One seasonal pass keeps a slow grower looking its best without fuss.
Pruning
Keep pruning light, shearing in late spring or early summer to hold a hedge's clean line. Never cut into bare old wood, which will not return, and tie up or wrap multi-stem plants before winter so snow and ice cannot break the form apart.
Repotting
As a fixture of the landscape, it is rarely repotted. Should one stand in a container, circling roots at the edge of the root ball, stalled new growth, or water running straight through signal that it has outgrown the pot.
Size & spacing
Expect a mature plant at 12 to 14 feet (3.7 to 4.3 m) tall and a trim 3 to 4 feet (91 to 122 cm) wide. For a seamless wall of green, set plants near enough that the slender crowns close together as they fill in.
When to plant
This is an evergreen for the long view, with no sowing season to track and no harvest to await, only a green form that holds its place year-round. Set new plants out in spring or early fall, when warm soil welcomes the roots, and pass over the heat of high summer or the hard middle of winter.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Plant: spring or early fall
- Harvest: Non-flowering; grown for evergreen foliage
Hardiness
USDA hardiness zones: 3–7
Temperature: down to -40°C
Troubleshooting
Most of what unsettles an arborvitae screen traces to winter or to a few familiar pests, and each leaves its own telltale mark. Browning foliage, stripped branches, and splayed stems each tell a different story, so look closely before stepping in. Match the symptom below and act while the screen can still recover.
Lower growth nibbled away by the time spring arrives
Lower branches left bare through winter are the work of deer browsing, and Emerald Green sits high on their cold-season menu. The damage reads as a ragged line up to about deer height, with tracks and droppings nearby, while rabbits account for the lowest foliage. Fence or net young plants before the snow falls, since hungry deer can hollow out a hedge once their other food runs short.
Fix:
- Install fencing or netting around plants
- Apply deer repellents and reapply after rain
- Wrap plants with burlap over winter
Small brown bags hanging from stripped branches
Small spindle-shaped sacks on bare branches are bagworms, the most damaging defoliator the plant faces. Each bag runs 1 to 2 inches long and wears scraps of foliage as cover, and the bags stir as the larvae feed in early summer. Pick them off through fall and winter to remove next year's eggs, and treat young larvae with Bt in late spring before a heavy run defoliates and kills the plant.
Fix:
- Handpick and destroy bags in fall and winter to remove overwintering eggs
- Apply Bacillus thuringiensis (Bt) to young larvae in late spring or early summer
- Use labeled insecticide for larger infestations
A dull, browning tree in ground that never dries
A browning, declining plant in waterlogged soil is showing root rot. Ease into the root ball and the roots come up dark, soft, and mushy rather than firm and white. Improve the drainage, ease off the water, and replant badly hit specimens where the ground drains freely, though the surest safeguard is to keep this tree clear of low spots that pool water.
Fix:
- Improve drainage around the root zone
- Avoid overwatering
- Replace severely affected plants in well-drained sites
Wind-facing foliage gone bronze and crisp by late winter
Bronzed, dried foliage on the sun and wind side is winter burn, the result of needles losing water faster than frozen roots can replace it on an exposed site. It appears late winter to early spring, and while 'Smaragd' holds its color better than the plain species, a harsh corner still scorches it. Water deeply in fall before the ground freezes, screen with burlap where wind is fierce, and prune out the dead brown once new growth returns, though a touch of plain winter bronzing is normal and greens up unaided.
Fix:
- Water deeply in fall before ground freezes
- Wrap or screen with burlap on exposed sites
- Prune out dead brown areas in spring once new growth resumes
A heavy snowfall leaves the trunks splayed or cracked
Heavy snow and ice can pry a multi-stem plant apart, bending the leaders outward or cracking them and breaking the clean line of a screen. Unwrapped specimens with several trunks bear the brunt. Brush snow off gently after storms, tie the stems with soft material, and wrap multi-stem plants before winter, or where snow is heavy, choose a single-leader plant that keeps its form far better.
Fix:
- Gently brush snow off branches after storms
- Tie stems together with soft material
- Stake or cable weakened leaders
Speckled, fading foliage laced with webbing in high summer
Fine stippling and a faint webbing across the foliage in hot, dry weather point to spider mites. Confirm them by tapping a branch over white paper and watching for tiny moving specks. Wash the foliage with a strong jet of water, follow with horticultural oil or a miticide if needed, and keep the soil moist, since a stressed plant invites them in.
Fix:
- Spray foliage with strong water jet to dislodge mites
- Apply horticultural oil or miticide
- Maintain adequate soil moisture to reduce stress
Toxicity
As a presence in a home with animals, Emerald Green carries low risk. Its foliage holds thujone oils that can mildly upset a pet that eats a good amount, though most animals turn away from the bitter taste. The item to keep well out of the way is any concentrated thuja essential oil, far more dangerous than the plant standing in the garden.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · People
Safe for
Birds
Cats Mild
A nibble of foliage usually passes with little fuss, but a cat that eats much may drool, vomit, or go off its food. Cats are the most sensitive of the household pets here, and concentrated thuja essential oil is far more dangerous than the plant, so keep any oil products well out of reach.
Dogs Mild
A curious dog that chews the foliage may drool or run an upset stomach for a while, though small tastes rarely cause more. The real hazard is the essential oil, never the odd mouthful of clippings.
Horses Mild
The thujone oils in the foliage can irritate a horse's stomach if it grazes the branches, bringing on mild colic or a dull appetite. Most horses leave the bitter foliage alone, so trouble appears only when little else is on offer.
Rabbits Mild
Rabbits should not be fed arborvitae, since the aromatic oils can unsettle a small digestive system. A stray nibble is unlikely to harm, but it has no place in their diet.
Livestock Mild
Cattle, goats, and sheep generally pass over the bitter foliage and come to no harm. Eaten in quantity, though, the thujone can mildly upset the gut, so prunings are best kept out of the pasture.
People Caution
Nothing on this evergreen belongs on a plate, and its thujone-laced foliage can bother stomach and skin alike. Teach little ones not to mouth the greenery, and pull on gloves for shearing sessions if the sap tends to leave your hands itchy.
Birds Safe
For garden birds the story is a happy one: the dense evergreen canopy offers nesting cover and shelter, with no hazard attached.
Keep clippings and any thuja essential oil products away from pets; the concentrated oil is the main concern.
Helpline numbers
United States
ASPCA Animal Poison Control: (888) 426-4435 (fee applies)
Poison Control: (800) 222-1222
Canada
Poison Centres: 1-844-764-7669
Varieties
Arborvitae offers a range of forms to suit a setting, from tall screening columns to small, rounded globes that anchor a bed. These are the cultivars worth considering as you shape a space.
'Green Giant'
A far larger, faster hybrid that rises to 40 to 60 feet at 3 to 4 feet a year and shrugs off the deer and disease that trouble the deer-favored 'Emerald Green'.
'Techny' (Mission)
A broad, dense pyramid in deep green that keeps its winter color and stands up to hard cold.
'North Pole'
A very narrow, columnar selection suited to tight vertical screens where space is at a premium.
'Holmstrup'
A patient, unhurried cultivar with a slim pyramid outline whose rich color stays put through the coldest months.
'Hetz's Midget'
A dwarf globe of only about 3 to 4 feet tall and wide, rounded rather than conical, ideal for a low accent.
'Danica'
A neat little sphere of green, sized to dress the base of a house without outgrowing its welcome.
How to propagate
Named cultivars like this one are raised from cuttings rather than seed, so each new plant repeats the parent's form, a continuity that matters when a screen has to read as one. Layering offers a slower route when only a plant or two is wanted.
Stem cuttingsModerate
Late summer to fall (semi-hardwood) or late winter (hardwood) · 6 to 12 weeks to root
Cuttings keep a named cultivar true to its parent, which seed cannot do. Take semi-hardwood cuttings in late summer or fall, or hardwood ones in late winter, dip them in rooting hormone to improve the odds, and expect roots in 6 to 12 weeks.
LayeringModerate
Spring · One growing season
A low branch pinned to the ground in spring will root in place over a single growing season. The method works, though cuttings remain the standard way to build up a planting of cultivars.
Myths
An Emerald Green screen is naturally deer-proof, like any other arborvitae.
Not so. Emerald Green is among the plants deer browse most often and most severely, with the pressure heaviest in winter once other food is gone. Only the hybrid 'Green Giant' is genuinely deer-resistant, so where deer pressure runs high, it is the screen to plant instead.