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 plant to turn to when a garden needs a tall, private edge and needs it soon. A hybrid evergreen in the cypress family, crossed from two Thuja species, it adds several feet a year once it has settled into its place. Set in a run along a boundary, the individual plants merge into a single green wall that softens wind, quiets road noise, and draws a calm line between a home and everything beyond it.
The name arborvitae hints at something modest, yet this is a tree on a landscape scale, rising 40 to 60 feet tall and broadening 12 to 18 feet wide in a tall, tapering pyramid that stays green right through winter. The 'Green Giant' name suits it. Give it a setting with real breathing room, and it holds that architectural presence with almost no fuss in return.
Much of its appeal is how effortless it is to live with. It stays clear of most pests and disease, deer tend to leave it be, and it takes to a wide range of soils and settings. The one place it struggles is a soggy, poorly drained corner, where root rot can undo the whole planting, so a well-drained spot is the foundation of a screen that lasts.
Care
The short version: set it in full sun on well-drained soil, allow room for the full 40 to 60 feet it will reach, and keep it watered through the first couple of years while the roots settle in.
Light
Green Giant looks its best in full sun, which keeps the screen full and dense from the ground to the tip. It manages in partial sun or light shade, but the deeper the shade, the thinner and looser the wall reads.
Water
Keep the soil moist through the first one to two years while the roots settle, watering roughly every 7 to 14 days. Once established it carries through short dry spells with ease, though steady moisture in well-drained soil is what keeps the growth quick and the screen filling in.
Soil
It is easygoing about its footing, taking clay, sand, and most everything between, so long as the ground drains. A moist, fertile, well-drained loam suits it best, and it settles happily across a wide pH range of 5.5 to 8.0.
Temperature
This is a cold-hardy tree at home from about -20°F to 100°F (-29°C to 38°C), covering USDA zones 5 through 8. It keeps its green through hard winters, though a cutting wind can scorch the foliage left out in the open.
Humidity
Ordinary outdoor air suits it perfectly, so there's no humidity to manage. What matters far more is good airflow between plants, since a crowded run traps moisture and invites trouble.
Feeding
In good soil it rarely calls for feeding at all. Where growth looks weak, work in a balanced slow-release tree fertilizer in spring, and leave a screen that is already thriving well enough alone.
Pruning
Green Giant needs little to no pruning and holds its handsome shape on its own. Shear in late spring or early summer only when keeping it as a formal hedge, and tie up or remove extra leaders so snow can't pull the line apart.
Repotting
This is a landscape tree, not a pot plant, so repotting rarely enters the picture. While it waits in a nursery pot, watch for roots circling or pushing out the drainage holes, the sign it is ready for its place in the ground.
Size & spacing
Plan around 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, and set a screen with that full spread in view. Space too tightly and the run turns crowded, with oversized plants pressed against the house and the lines above it.
When to plant
Grown for its year-round green rather than any flower or fruit, this evergreen keeps no seasonal show to schedule. Set new plants out in spring or fall, when the soil works easily and the weather stays mild, and let that gentler season settle the roots before summer heat or winter cold arrives.
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 well-placed Green Giant asks little, and the few troubles it meets tend to surface in the foliage or in the wake of a hard winter. Learning to read winter burn apart from a pest, or a wet-corner decline apart from drought, lets you tend the screen before a single plant lets the line down. Match what you see below, then act while it still counts.
A tree yellowing and thinning on a low, wet corner
When a plant on a low, water-holding corner of the garden fades all over, the trouble is usually root rot, often Phytophthora taking hold where the ground stays wet. Lift the soil and the roots read dark, soft, and discolored. There's no graceful recovery once it sets in, so the answer is to open up the drainage, ease off the watering, and remove any badly affected plants before the loss spreads down the line.
Fix:
- Improve drainage and stop overwatering
- Avoid planting in low, waterlogged spots
- Remove severely affected plants to limit spread
Scorched brown foliage revealed when winter lifts
The pale, browned patches are winter burn, and they settle on the side of the screen that faces the open wind and low sun. The foliage keeps releasing water through the cold while the frozen roots have none to return, so that tissue dries and fades rather than spotting. A deep autumn watering before the freeze, a layer of mulch across the root zone, and the patience to let spring reveal what survived will restore the wall's even, composed line.
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
Gaps opening in an otherwise smooth green screen often trace to evergreen bagworm caterpillars, which feed on the foliage and carry a made-to-order case wherever they travel. The tell is the case itself, 0.25 to 2 inches long and pieced together from the plant's own clippings, swinging from the twigs. Pick them off through fall and winter before the eggs hatch, and answer a fresh generation with a Bt spray in late spring to keep the hedge reading full and unbroken.
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 or snapped after a heavy snowfall
The tall, tapering silhouette that reads so beautifully in the landscape also collects snow and ice, and that weight can pull multiple leaders apart or break them off, spoiling the clean line. Brush the snow away before it sets and freezes, and gather the upright stems with soft ties so the form stays true. Choosing a single-leader plant from the outset keeps that graceful shape through the seasons.
Fix:
- Gently brush snow off before it accumulates and freezes
- Tie multiple leaders together with soft material for support
- Prune cleanly broken branches
Dulled, bronzed foliage veiled in fine webbing
A screen that looks tired and bronzed in the height of summer is often hosting spider mites, which draw the color from the foliage and leave it flat and dull under hot, dry skies. Hold white paper beneath a branch, tap, and watch for the minute specks that give them away. A firm jet of water clears most of them, horticultural oil settles a heavier visit, and steady watering through the heat is what keeps the hedge looking rested and fresh.
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 at home, though a passing nibble is more an upset stomach than a crisis. The foliage carries thujone, an oil that can irritate the stomach and skin of pets, livestock, and people. The genuine hazard is concentrated arborvitae essential oil, which should never be left within an animal's reach.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds · People
Cats Mild
A cat that samples the foliage tends to show a little drooling, an unsettled stomach, or some diarrhea, courtesy of the thujone oil the leaves hold. A passing taste is a far smaller concern than the concentrated essential oil, which deserves real caution.
Dogs Mild
A dog drawn to chew the foliage may drool, be sick, or run loose stools and seem low for a while, and it usually settles on its own. The concentrated arborvitae oil is the one to store well out of a curious dog's reach.
Horses Mild
A horse that browses the foliage can pick up a mild stomach upset, little more than that. It sits on the list of plants to keep them from, though a casual taste rarely amounts to anything serious.
Rabbits Mild
The thujone that unsettles cats and dogs will do the same to a rabbit's digestion, so browsing on the foliage is worth heading off. Its familiar greens are the better offering.
Livestock Mild
Cattle, goats, and sheep generally pass over the bitter foliage, but a hungry animal that strips a branch may take on enough oil for some digestive upset. A fence around young plantings keeps everyone at ease.
Birds Caution
Birds settle contentedly into the dense canopy without any harm, and they show no interest in the foliage as food. The only real caution is keeping concentrated thuja oil away from them.
People Caution
No part of this plant belongs on a plate, and the leaves can leave the stomach and skin irritated. Reach for gloves if the sap troubles you at shearing time, and keep the concentrated essential oil clear of 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 grandest of the popular arborvitae, and a few close relatives suit the gardens and corners where it would simply be too much. These are the ones worth having in mind.
'Emerald Green' ('Smaragd')
Where Green Giant would overwhelm a smaller garden, this more compact Thuja occidentalis settles around 10 to 15 feet tall and 3 to 4 feet wide, keeping to a gentler scale.
'Spring Grove'
Grown much the way Green Giant is, this is another fast, large pyramidal arborvitae that quickly reads as a finished privacy screen.
'American Pillar' (Thuja occidentalis 'Pillar')
For a slim vertical accent along a narrow run, this columnar form suits the space far better than the broad-shouldered Green Giant.
How to propagate
There is really one practical way to build a matched screen of 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
Being a sterile cultivar with no seed to offer, Green Giant comes only from cuttings, which is how every plant in a matched screen shares the same clean line. Take semi-hardwood cuttings in late summer or fall and give them several weeks to a few months to root before growing them on.
Myths
Green Giant arborvitae is a tidy little hedge plant.
It reads as a neat hedge in the nursery, but this is a fast-growing forest tree rather than a foundation shrub. It reaches 40 to 60 feet tall and 12 to 18 feet wide, so it wants a setting with room to breathe. Place it as a small hedge and it will simply consume the space.
Arborvitae will spread and become invasive.
There's no cause for concern here. 'Green Giant' is a sterile hybrid, sets no viable seed, and has no route into the wider landscape. It holds exactly to the spot you give it.