Tree · Cupressaceae
Emerald Green Arborvitae
Thuja occidentalis
Pop it into full sun with steady moisture, keep deer and snow at bay, and you've got a dense green screen for decades.
Full sun
Every 5–10 days
USDA 3–7
12–14 ft · 3.7–4.3 m
Overview
You know those slim evergreens lined up to screen a yard across the cold north? That's Emerald Green Arborvitae. It's a 'Smaragd' pick of the eastern white cedar, Thuja occidentalis, and it keeps a neat pyramid of bright green foliage all year long. It tops out around 12 to 14 feet (3.7 to 4.3 m) tall and stays just 3 to 4 feet (91 to 122 cm) wide, which is why it fits a property line so well.
Here's the easy part: it grows slow and steady, so once it's settled in it barely asks for anything. Cold? Not a worry, since it takes -40°F (-40°C) in stride, and it'll grow in all sorts of soil, even heavy clay, as long as water drains away. What it won't put up with is drought or soggy feet.
So what's the catch? Winter and wildlife, mostly. Deer treat it like a snack, a big snow can splay a multi-stem plant open, and a dry, windy corner will brown the foliage. Get the spot right and do a little winter prep, though, and the rest is easy hedging for years.
Care
The short version: full sun to light shade, soil kept evenly moist but never waterlogged, and a deep drink in fall before the ground freezes. Keep deer and harsh winter wind away, and tie up multi-stem plants before the snow shows up.
Light
Give it full sun and it grows the fullest and healthiest, but it'll take partial shade too without much fuss. Just know that when the light gets too thin, the foliage starts to open up and you end up with gaps in your screen.
Water
Keep the soil consistently moist and well drained, and water it deeply every 5 to 10 days when things get dry. It really can't handle drought or a dry, windy spot, so don't skip a good fall soak before the ground freezes, since that's what keeps it from drying out over winter.
Soil
It's happy in moist, fertile, well-drained loam, and it'll even tolerate clay as long as water doesn't sit. The pH it likes is nice and wide, 6.0 to 8.0, which covers pretty much any garden soil from a bit acidic to alkaline.
Temperature
Cold isn't going to bother this one. It comes through anywhere from -40°F to 100°F (-40°C to 38°C), and that's exactly why it works as a hedge way up north.
Humidity
Regular outdoor humidity is fine, so there's no number to worry about. What actually matters is airflow and steady soil moisture, way more than how damp the air is.
Feeding
Feed it once in spring with a balanced, slow-release evergreen fertilizer and you're done. One go each season is plenty for something that grows this slowly.
Pruning
Keep it light, just a shear in late spring or early summer to shape your hedge. Don't cut back into bare old wood, because it won't grow back, and tie up or wrap multi-stem plants before winter so snow and ice can't splay them apart.
Repotting
This is a long-haul landscape plant, so it's rarely repotted. If you've got one in a pot, though, circling roots at the edge of the root ball, stunted growth, or water shooting straight through are your cues that it's outgrown its home.
Size & spacing
Figure on a grown plant around 12 to 14 feet (3.7 to 4.3 m) tall and just 3 to 4 feet (91 to 122 cm) wide. Want a solid screen? Set them close enough that those narrow crowns can grow together as they fill in.
When to plant
There's no sowing season and no harvest here, so this one's about as low-key as planting gets. Put new plants out in spring or early fall while the soil's still warm enough for roots to settle, and just steer clear of high summer heat or the dead 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 arborvitae headaches come down to winter or a few usual-suspect pests. The trick is to read the clues before you act, since browning foliage, stripped branches, and splayed stems all mean different things. Find your symptom below and jump on it early.
Lower branches stripped bare over the winter
If the lower branches got stripped over winter, that's almost always deer browsing, and Emerald Green is one of their go-to winter snacks. You'll spot a ragged line chewed up to about deer height, usually with tracks and droppings around, and rabbits will nibble the very bottom too. Fence or net young plants before the snow comes, because once their other food runs out, hungry deer can hollow out a whole hedge.
Fix:
- Install fencing or netting around plants
- Apply deer repellents and reapply after rain
- Wrap plants with burlap over winter
Little brown bags hanging off thinning branches
Those little spindle-shaped sacks? Those are bagworms, and they're the worst defoliator this plant deals with. Each bag's about 1 to 2 inches long and covered in bits of foliage for camo, and you'll catch them twitching when the larvae feed in early summer. Pick the bags off through fall and winter to get rid of next year's eggs, and hit young larvae with Bt in late spring before a big batch 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
Fading plant just sitting in soggy ground
When the soil stays waterlogged, root rot sets in and the foliage browns as the plant slides downhill. Dig around the root ball and you'll find dark, soft, mushy roots instead of firm white ones. Fix the drainage, ease off the watering, and move the badly hit ones somewhere that drains well, but really, the surest fix is just keeping this tree out of low spots that pool water.
Fix:
- Improve drainage around the root zone
- Avoid overwatering
- Replace severely affected plants in well-drained sites
Bronzed, dried foliage on the windy side after winter
Brown, dried-out foliage on the windy, sunny side is winter burn, which is just the needles losing water faster than frozen roots can put it back. It usually shows up late winter into early spring, and while 'Smaragd' holds its color better than the plain species, a really exposed spot will still scorch it. Water deeply in fall before the ground freezes, screen it with burlap where the wind's brutal, and trim out the dead brown once new growth comes back, and don't panic over a little plain winter bronzing, since that greens right back up 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
Stems splayed open or snapped after a snow load
Heavy snow and ice can pry a multi-stem plant apart, bending the leaders out or even cracking them, and it's the unwrapped trees with a few trunks that take the worst of it. Brush snow off gently after a storm, tie the stems together with something soft, and wrap multi-stem plants before winter. Live somewhere snowy? A single-leader plant holds its shape a whole lot better.
Fix:
- Gently brush snow off branches after storms
- Tie stems together with soft material
- Stake or cable weakened leaders
Stippled, yellowing foliage with fine webbing in the heat
When it's hot and dry and you see fine speckling with a faint webbing on the foliage, that's usually spider mites moving in. Want to be sure? Tap a branch over white paper and look for tiny crawling specks. Blast the foliage with a strong jet of water, follow up with horticultural oil or a miticide if you need to, and keep the soil moist, because a stressed plant is exactly what pulls mites in.
Fix:
- Spray foliage with strong water jet to dislodge mites
- Apply horticultural oil or miticide
- Maintain adequate soil moisture to reduce stress
Toxicity
Good news for pet households: Emerald Green is a pretty low-risk plant. Its foliage has thujone oils that can give a pet a mild tummy upset if they eat a fair bit, but honestly, most animals don't like the bitter taste. The thing you really want to put away is any concentrated thuja essential oil, which is way more dangerous than the plant.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · People
Safe for
Birds
Cats Mild
A little nibble usually goes by without much fuss, but a cat that eats a lot can drool, throw up, or lose interest in food. Cats are the most sensitive of the household pets here, and concentrated thuja essential oil is way 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 have an upset stomach for a bit, though small tastes hardly ever cause more than that. The real danger's the essential oil, not the odd mouthful of clippings.
Horses Mild
The thujone oils in the foliage can bug 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 only really shows up when there's not much else around.
Rabbits Mild
Don't feed rabbits arborvitae, since the aromatic oils can upset a small digestive system. A stray nibble probably won't hurt, but it's got no place in their diet.
Livestock Mild
Cattle, goats, and sheep mostly skip the bitter foliage and come to no harm. Eat enough of it, though, and the thujone can mildly upset the gut, so it pays to keep prunings out of the pasture.
People Caution
No part of this tree's meant to be eaten, and the thujone in the foliage can irritate the stomach and skin. Keep kids from chewing the leaves, and throw on gloves if the sap leaves your skin itchy when you shear a hedge.
Birds Safe
Backyard and wild birds shelter and nest in the dense foliage no problem, and the plant's no real risk to them.
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 comes in a bunch of shapes, from tall screens right down to little tidy globes. Here are the cultivars worth a look when you're picking one for a spot.
'Green Giant'
It's a way bigger, faster hybrid that hits 40 to 60 feet at 3 to 4 feet a year, and it shrugs off the deer and disease that give deer-favored 'Emerald Green' so much grief.
'Techny' (Mission)
It's a broad, dense pyramid in deep green that hangs onto its winter color and takes hard cold without blinking.
'North Pole'
It's a really narrow, columnar pick made for tight vertical screens when you're short on room.
'Holmstrup'
It's a slow, compact, narrowly pyramidal cultivar that keeps its rich green right through winter.
'Hetz's Midget'
It's a little dwarf globe, only about 3 to 4 feet tall and wide, and rounded instead of conical.
'Danica'
It's a compact dwarf globe people grow as a small, rounded accent by a foundation.
How to propagate
Named cultivars like this one come from cuttings, not seed, so the new plant turns out just like the parent. Need only one or two? Layering's a slower but easy backup.
Stem cuttingsModerate
Late summer to fall (semi-hardwood) or late winter (hardwood) · 6 to 12 weeks to root
Cuttings are how you keep a named cultivar matching its parent, since seed just won't do it. Take semi-hardwood cuttings in late summer or fall, or hardwood ones in late winter, dip them in rooting hormone to boost your chances, and you'll usually see roots in 6 to 12 weeks.
LayeringModerate
Spring · One growing season
You can also pin a low branch down to the ground in spring and let it root right there over a single growing season. It works fine, but cuttings are still the usual way to bulk up cultivars.
Myths
Every arborvitae, Emerald Green included, is deer-proof.
Not even close. Emerald Green is actually one of the plants deer go after most often and most hard, and they hit it worst in winter when everything else is gone. Only the hybrid 'Green Giant' is really deer-resistant, so if deer are a big problem where you are, plant that one instead.