Tree · Cupressaceae
Emerald Green Arborvitae
Thuja occidentalis
Plant it in full sun with steady moisture, stay a step ahead of deer and snow, and it grows you a dense green screen 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 slim evergreen that turns a bare property line into a living wall of green right across the cold north. It is a 'Smaragd' selection of the eastern white cedar, Thuja occidentalis, and it powers out a tight pyramid of bright green foliage that never quits, summer or winter. A mature plant climbs to about 12 to 14 feet (3.7 to 4.3 m) tall while holding a lean 3 to 4 feet (91 to 122 cm) wide, so it packs real height into a narrow footprint.
The growing is genuinely rewarding because the plant does so much of the work. It grows slow and steady, settles in fast, and then coasts on very little. It laughs off cold down to -40°F (-40°C) and roots into all kinds of soil, heavy clay included, as long as the ground drains. Just keep it off two extremes: bone-dry drought and a swampy root zone.
Winter and wildlife are where the fun of outsmarting nature comes in. Deer hunt it down, big snows can splay a multi-stem plant, and a dry, windy corner browns the foliage. Pick a smart spot, prep it well for winter, and you set yourself up for easy hedging for years.
Care
The short version: full sun to light shade, soil kept evenly moist but never waterlogged, and a deep soak in fall before the ground freezes. Outflank the deer and the harsh winter wind, and tie up multi-stem plants ahead of the snow.
Light
Hand it full sun and it rockets into the densest, healthiest growth, though it will happily take partial shade too. Skimp on light, though, and the foliage thins out and opens gaps in a screen you want solid.
Water
Keep that soil consistently moist and well drained, and soak it deeply every 5 to 10 days when dry weather rolls in. It simply will not stand drought or dry, windy exposure, so treat it to a thorough fall soak before the ground freezes and beat winter desiccation to the punch.
Soil
It digs into moist, fertile, well-drained loam and even powers through clay, as long as water keeps moving instead of pooling. The pH range runs wide and easy, 6.0 to 8.0, so most garden ground from slightly acidic to alkaline gives it a great start.
Temperature
Cold barely registers with this one. It charges through anything from -40°F to 100°F (-40°C to 38°C), the very toughness that lets it hold a hedge across the far north.
Humidity
Plain outdoor humidity suits it fine, so there is no number to chase. Airflow and steady soil moisture do far more for it than however damp the air happens to be.
Feeding
Hit it once in spring with a balanced, slow-release evergreen fertilizer and call it good. One seasonal feed fuels a slow grower like this with plenty to spare.
Pruning
Keep the shears light, trimming in late spring or early summer to sharpen a hedge. Never carve into bare old wood, which will not bounce back, and tie up or wrap multi-stem plants before winter so snow and ice cannot splay them apart.
Repotting
As a long-haul landscape plant, it gets rarely repotted. Grow one in a pot, though, and roots circling the root ball, stalled new growth, or water blasting straight through tell you it has outgrown its container.
Size & spacing
Aim for a mature plant 12 to 14 feet (3.7 to 4.3 m) tall and a slim 3 to 4 feet (91 to 122 cm) wide. Want a wall with no gaps? Set plants close enough that those narrow crowns knit together as they fill in.
When to plant
Forget sowing seasons and harvests, because this evergreen has neither, and that is part of the appeal. Get new plants in the ground in spring or early fall so the roots dig in while the soil is warm, and just dodge the peak of summer heat and the depths 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
Nearly every arborvitae hiccup traces straight back to winter or a handful of familiar pests, and each one practically announces itself. Browning foliage, stripped branches, and splayed stems each flag a different cause, so read the clues before you dive in. Pin down the symptom below and pounce on it early.
Lower growth gnawed off through the cold months
Stripped lower branches in winter scream deer browsing, and Emerald Green tops their cold-season menu. Hunt for a ragged line chewed up to about deer height, with tracks and droppings nearby, and watch rabbits clean off the lowest foliage too. Fence or net young plants before the snow lands, because hungry deer will hollow out a hedge the moment 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
Twig-covered brown bags swinging from bare shoots
Those little spindle-shaped sacks are bagworms, the fiercest defoliator this plant ever meets. Each bag stretches 1 to 2 inches long and wears scraps of foliage as a disguise, and you will catch them twitching as the larvae chow down in early summer. Pluck the bags off through fall and winter to wipe out next year's eggs, and zap young larvae with Bt in late spring before a big wave strips 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
Whole plant fading to brown in ground that stays wet
Let the soil stay waterlogged and root rot moves in, browning the foliage as the plant slides downhill. Dig at the root ball and you will turn up dark, soft, mushy roots where firm white ones belong. Sharpen up the drainage, back off the water, and relocate badly hit plants to ground that drains freely, but the real win is keeping 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
Sun-and-wind side turned bronze and dry after winter
Bronzed, dried foliage on the sun and wind side is winter burn, the fallout when needles lose water faster than frozen roots can pump it back on an exposed site. It flares up late winter into early spring, and while 'Smaragd' guards its color better than the plain species, a brutal spot still scorches it. Soak it deeply in fall before the ground freezes, screen it with burlap where the wind rips, and snip out the dead brown once new growth fires back up, knowing a little plain winter bronzing is normal and greens right back on its own.
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
Splayed or cracked leaders once the snow piles up
Heavy snow and ice can wrench a multi-stem plant apart, bowing the leaders outward or cracking them, and unwrapped specimens with several trunks take the hardest hit. Knock the snow off gently after storms, lash the stems together with soft material, and wrap multi-stem plants before winter. In snowy country, a single-leader plant holds its shape far better and saves you the cleanup.
Fix:
- Gently brush snow off branches after storms
- Tie stems together with soft material
- Stake or cable weakened leaders
Stippled sprays and faint webbing when the heat sets in
Spider mites charge in during hot, dry stretches, dusting the foliage with fine speckling and faint webbing. Nail down the diagnosis by tapping a branch over white paper and spotting the tiny crawling specks. Blast the foliage with a hard jet of water, chase it with horticultural oil or a miticide if they hang on, and keep the soil moist, since a stressed plant rolls out the welcome mat for mites.
Fix:
- Spray foliage with strong water jet to dislodge mites
- Apply horticultural oil or miticide
- Maintain adequate soil moisture to reduce stress
Toxicity
Here is the upside for animal lovers: Emerald Green is a low-risk plant to grow around pets. Its foliage carries thujone oils that can mildly upset a stomach if a pet eats a real mouthful, but most animals snub the bitter leaves anyway. The one thing to stash safely away is any concentrated thuja essential oil, which packs a far bigger punch than the plant ever does.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · People
Safe for
Birds
Cats Mild
A quick nibble of foliage usually passes with little fuss, but a cat that eats much can 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 might drool or run an upset stomach for a while, though small tastes rarely cause more than that. 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, sparking mild colic or a dull appetite. Most horses steer clear of the bitter foliage, so trouble crops up only when little else is on offer.
Rabbits Mild
Skip feeding rabbits arborvitae altogether, since the aromatic oils can unsettle a small digestive system. A stray nibble is unlikely to do harm, but it has no place in their diet.
Livestock Mild
Cattle, goats, and sheep mostly march right past the bitter foliage and come to no harm. Eaten in quantity, though, the thujone can mildly upset the gut, so keep prunings out of the pasture.
People Caution
No part of this tree is meant to be eaten, and the thujone in the foliage can irritate the stomach and skin. Keep children from chewing the leaves, and pull on gloves if the sap leaves your skin itchy when you shear a hedge.
Birds Safe
Songbirds make the most of that dense screen, tucking nests deep among the branches, and the plant does them no harm at all.
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 bursts into all kinds of shapes, from soaring screens to neat little globes. Here are the cultivars worth chasing down when you pick one for a spot.
'Green Giant'
A far bigger, faster hybrid that shoots up to 40 to 60 feet at 3 to 4 feet a year and brushes off the deer and disease that hound deer-favored 'Emerald Green'.
'Techny' (Mission)
A broad, dense pyramid in deep green that locks onto its winter color and powers through hard cold.
'North Pole'
A super-narrow, columnar pick built for tight vertical screens where every inch counts.
'Holmstrup'
A slow, compact, narrowly pyramidal cultivar that grips its rich green right through winter.
'Hetz's Midget'
A pint-sized dwarf globe of only about 3 to 4 feet tall and wide, rounded instead of conical.
'Danica'
A little charmer of a dwarf globe that brings a tidy round pop of green to a foundation bed.
How to propagate
Named cultivars like this one come from cuttings, not seed, so every new plant springs up as a perfect copy of the parent. Layering makes an easy fallback when you only want a plant or two.
Stem cuttingsModerate
Late summer to fall (semi-hardwood) or late winter (hardwood) · 6 to 12 weeks to root
Cuttings are your ticket to keeping a named cultivar dead-on to its parent, since seed never will. Snip semi-hardwood cuttings in late summer or fall, or hardwood in late winter, dunk the ends in rooting hormone to stack the odds, and watch for roots in 6 to 12 weeks.
LayeringModerate
Spring · One growing season
Pin a low branch down to the ground in spring and let it root right where it sits over a single growing season. It works a treat, though cuttings stay the go-to for bulking up cultivars.
Myths
No deer will ever bother an arborvitae, Emerald Green or otherwise.
Not a chance. Emerald Green lands among the plants deer browse most often and most savagely, and they tear into it hardest in winter once other food vanishes. Only the hybrid 'Green Giant' truly shrugs deer off, so reach for that one wherever deer pressure runs high.