Tree · Cupressaceae
Green Giant Arborvitae
Thuja 'Green Giant'
Give it full sun and room to spread, and this tree throws up a living privacy wall fast.
Full sun
Every 7–14 days
USDA 5–8
40–60 ft · 12.2–18.3 m
Overview
Green Giant arborvitae is the go-to plant when you want a tall, dense screen in a hurry. It's a hybrid evergreen in the cypress family, a cross of two Thuja species, and it can put on several feet of growth a year once it settles in. A row of them turns into a solid green wall that blocks wind, noise, and the neighbor's view.
Don't let the word arborvitae fool you into thinking small. This is a forest-scale tree that climbs to 40 to 60 feet tall and spreads 12 to 18 feet wide, with a narrow pyramid shape and soft, scale-like foliage that stays green all winter. The 'Green Giant' name is earned. Give it the space it actually needs and it asks for almost nothing in return.
It earns its popularity by being tough and easy. It shrugs off most pests and disease, deer tend to leave it alone, and it handles a wide range of soils. The main thing it won't forgive is a soggy, poorly drained spot, where root rot sets in and takes the whole plant down.
Care
The short version: plant it in full sun in well-drained soil, give it room to reach its full 40 to 60 feet, and keep it watered through the first couple of years while the roots take hold.
Light
Green Giant grows best in full sun, where it stays dense from top to bottom. It puts up with partial sun or light shade, but the more shade it gets, the thinner and looser the foliage turns.
Water
Keep the soil moist for the first one to two years while the roots establish, watering roughly every 7 to 14 days. Once it's settled, it can ride out short dry spells, though steady moisture in well-drained soil is what drives the fastest growth.
Soil
It isn't fussy and takes clay, sand, and most everything between, as long as the ground drains. A moist, fertile, well-drained loam is the sweet spot, and it handles a wide pH band from 5.5 to 8.0.
Temperature
This is a cold-hardy tree, comfortable from about -20°F to 100°F (-29°C to 38°C), which covers USDA zones 5 through 8. It holds its color through hard winters, though biting wind can scorch the exposed foliage.
Humidity
Ordinary outdoor air suits it fine, so there's no humidity target to hit. Good airflow between plants matters more, since crowding traps moisture and invites trouble.
Feeding
In decent soil it rarely needs feeding at all. If growth looks weak, work in a balanced slow-release tree fertilizer in spring, but skip it on plants that are already growing well.
Pruning
Green Giant needs little to no pruning and holds its shape on its own. Shear it in late spring or early summer only if you're keeping it as a hedge, and tie up or remove extra leaders so snow can't pull them apart.
Repotting
This is a landscape tree, not a container plant, so repotting rarely comes up. In a nursery pot, watch for roots circling or pushing out the drainage holes, the cue to get it in the ground.
Size & spacing
Plan for a mature tree of 40 to 60 feet (12 to 18 m) tall and 12 to 18 feet (3.7 to 5.5 m) wide. Space a screen with that full spread in mind, or you'll end up with crowded, oversized plants pressed against the house and lines.
When to plant
This is an evergreen grown for its foliage, so there's no bloom or harvest to time. Set new plants out in spring or fall, when the soil is workable and the weather is mild, and let the cooler season help the roots establish before summer heat or winter cold sets in.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Plant: spring or fall
- Harvest: non-flowering (grown for evergreen foliage)
Hardiness
USDA hardiness zones: 5–8
Temperature: down to -29°C
Troubleshooting
A healthy Green Giant rarely gives you trouble, but the problems it does get show up in the foliage or after a rough winter. Learn to tell winter burn from a pest and a wet-site decline from drought stress, and you can step in before any of it spreads. Match what you see below, then act while it still helps.
Yellowing, thinning foliage and a tree in slow decline
When the whole plant fades on a wet, heavy site, the cause is usually root rot, often Phytophthora taking hold in soggy ground. Dig and you'll find dark, soft, discolored roots. There's no easy save once it sets in, so improve the drainage, stop overwatering, and pull badly affected plants to keep it from spreading.
Fix:
- Improve drainage and stop overwatering
- Avoid planting in low, waterlogged spots
- Remove severely affected plants to limit spread
Brown, scorched foliage showing up after a hard winter
This is winter burn, and it strikes the wind- and sun-facing side hardest. The foliage keeps losing water while the frozen roots can't pull any up, so the tissue dries out and bleaches rather than spotting. Water deeply in fall before the ground freezes, mulch the root zone, and wait until new spring growth shows what survived before you cut anything back.
Fix:
- Water deeply in fall before the ground freezes
- Prune out clearly dead tissue once new spring growth shows what survived
- Apply mulch over the root zone to extend water uptake
Thinning branches hung with small spindle-shaped bags
Those little cones are the work of evergreen bagworm caterpillars, which strip the foliage and carry their cover with them. Look for the bags, 0.25 to 2 inches long and made from bits of the plant itself, dangling from the twigs. Pick them off through fall and winter before the eggs hatch, and hit young larvae with Bt in late spring if they return.
Fix:
- Hand-pick and destroy bags in fall, winter or early spring before eggs hatch
- Spray Bacillus thuringiensis (Bt) on young larvae in late spring/early summer, repeating every 7 to 14 days
Branches splayed open or snapped after a snowstorm
The narrow pyramid catches snow and ice, and the weight pulls multiple leaders apart or cracks them clean off. Brush snow away before it piles up and freezes, and tie upright stems together with soft material so they hold their shape. Choosing a single-leader plant from the start spares you most of this trouble.
Fix:
- Gently brush snow off before it accumulates and freezes
- Tie multiple leaders together with soft material for support
- Prune cleanly broken branches
Dull, bronzed foliage flecked with fine webbing
Hot, dry spells bring out spider mites, which suck the color out of the foliage and leave it stippled and bronze. Tap a branch over a sheet of white paper and watch for tiny specks crawling across it. A hard jet of water knocks them loose, and horticultural oil handles a heavy run, but keeping the plant watered through the heat is the best defense.
Fix:
- Spray foliage with a strong jet of water to dislodge mites
- Treat heavy infestations with horticultural oil or miticide
Toxicity
Green Giant arborvitae is best kept off the menu, though a casual nibble is more a stomach upset than an emergency. The foliage carries thujone, an oil that can irritate the stomach and skin of pets, livestock, and people. The real hazard is concentrated arborvitae essential oil, which should never be left where animals can reach it.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds · People
Cats Mild
A nibble of foliage usually just means some drooling, an upset stomach, or a bout of diarrhea. The thujone oil in the leaves is what causes it, so a curious chew is far less worrying than the concentrated essential oil.
Dogs Mild
Dogs that chew the foliage tend to drool, throw up, or get loose stools and act sluggish for a while. It clears on its own in most cases, but keep the concentrated arborvitae oil well out of reach.
Horses Mild
The foliage can leave a horse with a mild stomach upset if it browses on it. It's listed as a plant to keep them away from, though serious trouble is rare from a casual taste.
Rabbits Mild
The same thujone that bothers cats and dogs can give a rabbit an upset stomach, so don't let it browse the foliage. Stick to its usual greens instead.
Livestock Mild
Cattle, goats, and sheep generally leave the bitter foliage alone, but a hungry animal that strips a branch may get a touch of digestive upset from the oils. Fence them off from young plantings.
Birds Caution
Birds shelter happily in the dense branches without harm. The foliage isn't a food they'd seek out, so the main caution is keeping any concentrated thuja oil away from them.
People Caution
No part of the plant is meant to be eaten, and the leaves can irritate the stomach and skin. Wear gloves if the sap bothers you when shearing, and keep the concentrated essential oil away from children.
Keep pets from chewing foliage and never apply or leave out concentrated thuja/arborvitae essential oil around animals; oral exposure is the highest-risk route.
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
Green Giant is the largest of the popular arborvitae, but a few relatives cover the spots where it would be too big. These are the ones worth knowing by name.
'Emerald Green' ('Smaragd')
A much smaller Thuja occidentalis that tops out around 10 to 15 feet tall and 3 to 4 feet wide, made for tighter spots where Green Giant would crowd everything out.
'Spring Grove'
Another fast, large pyramidal arborvitae grown the same way Green Giant is, as a quick privacy screen.
'American Pillar' (Thuja occidentalis 'Pillar')
A very narrow column that suits tight vertical screens, far slimmer than the broad-shouldered Green Giant.
How to propagate
There's only one practical way to make more Green Giants, since the plant sets no seed of its own.
Stem cuttingsModerate
Late summer to fall (semi-hardwood cuttings) · Several weeks to a few months to root
Because the cultivar is sterile, there's no seed to sow, so every Green Giant comes from a cutting. Take semi-hardwood cuttings in late summer or fall, and give them anywhere from a few weeks to a few months to root before they're ready to grow on.
Myths
Green Giant arborvitae is a tidy little hedge plant.
This is a fast-growing forest tree, not a foundation shrub. It runs 40 to 60 feet tall and 12 to 18 feet wide, so it needs real room. Plant it as a small hedge and it will swallow the space whole.
Arborvitae will spread and turn invasive.
'Green Giant' is a sterile hybrid, so it sets no viable seed and has no way to escape into the wild. It stays exactly where you plant it.