How To Grow Green Giant Arborvitae: The Complete Care Guide

Introduction

Learning how to grow green giant arborvitae is one of the most rewarding decisions a homeowner can make when fast, elegant privacy is the goal. This hybrid evergreen — a cross between Japanese arborvitae (Thuja standishii) and western red cedar (Thuja plicata) — was first propagated at the U.S. National Arboretum in the 1960s and released to the nursery trade in 1967. It has since become one of the most popular screening trees in North America, prized for its vigorous growth rate of up to five feet per year, dense pyramidal form, and rich dark-green foliage that holds its color through winter without the bronzing common in many other arborvitae cultivars.

Green giant arborvitae offers year-round architectural structure with its naturally symmetrical, conical silhouette. The sprays of glossy, scale-like foliage create a soft yet impenetrable visual barrier, making the tree ideal for windbreaks, privacy hedges, and specimen plantings. It thrives across a broad swath of the United States, from the mid-Atlantic to the Pacific Northwest, and its exceptional resistance to deer browsing, ice damage, and bagworms sets it apart from competitors like Leyland cypress.

Growing Conditions & Requirements

Hardiness Zones and Climate

Green giant arborvitae performs best in USDA hardiness zones 5 through 8, tolerating winter lows down to approximately −20 °F (−29 °C). It thrives in the humid summers of the Southeast, the moderate winters of the mid-Atlantic, and the Pacific Northwest’s cool maritime climate. In zone 8, adequate moisture is important because prolonged heat above 95 °F can stress newly planted trees. In zone 5, selecting a site sheltered from desiccating winter winds helps prevent foliar burn.

Light Requirements

Full sun — a minimum of six hours of direct sunlight daily — produces the densest, most uniform growth. Green giant arborvitae tolerates partial shade (four to six hours of sun), but shaded specimens grow more open and may develop bare patches along lower branches over time. For a solid privacy screen, always position the planting line where it will receive maximum light exposure.

Soil Preferences

This cultivar is remarkably adaptable to a wide range of soil types, from sandy loams to heavy clays, provided drainage is adequate. Ideal soil pH ranges from 6.0 to 8.0 — slightly acidic to slightly alkaline. Constantly saturated or waterlogged soils are the primary cause of root rot and early decline. If your property has heavy clay, amending the planting area with compost or planting on a slight berm improves drainage significantly. Knowing how to read your soil conditions is half the battle; understanding soil indicators can guide your site preparation.

Spacing and Growth Rate

For a continuous privacy hedge, space green giant arborvitae 5 to 6 feet apart, center to center. For a more informal screen with visible individual outlines, increase spacing to 8 to 10 feet. As specimen trees, allow 12 to 15 feet between plants to let each develop its full pyramidal canopy. Young trees commonly add 3 to 5 feet of height annually under favorable conditions, slowing somewhat as they approach maturity. Expect plants to reach 40 to 60 feet tall and 12 to 20 feet wide at maturity, though some specimens in ideal conditions can exceed 60 feet.

Planting & Establishment

Best Planting Times

The optimal planting window is early to mid-fall (September through October) in most regions, which gives root systems several months to establish before the heat of summer. Early spring, after the ground has thawed and before new growth begins, is the second-best option. In zone 5, spring planting is often preferred to give roots a full growing season before winter. Understanding the best time to plant shrubs in your specific zone will help you get the timing right for trees as well.

Site Selection and Soil Preparation

Choose a location with full sun exposure, adequate air circulation, and soil that does not remain soggy after rainfall. Avoid low-lying areas where water collects. Before planting, conduct a simple drainage test: dig a hole 12 inches deep, fill it with water, and observe how quickly it drains. If water remains after 4 to 6 hours, amend with coarse organic matter or select an alternative site.

Planting Instructions

Dig a hole two to three times wider than the root ball but only as deep as the root ball’s height. The root flare — where the trunk begins to widen at the base — should sit at or slightly above the surrounding soil grade. Backfill with native soil, firming gently to eliminate air pockets. Water deeply immediately after planting, saturating the entire root zone. Apply 2 to 3 inches of organic mulch (shredded bark or wood chips) in a ring around the base, keeping mulch 3 to 4 inches away from the trunk to prevent moisture-related bark decay.

Establishment Period

Green giant arborvitae typically requires one to two growing seasons to become fully established. During this period, consistent weekly watering — about 1 inch per week — is essential, especially during dry spells. Once roots have spread well beyond the original root ball, the tree becomes moderately drought tolerant.

Propagation Methods

Vegetative Propagation (Cuttings)

Because green giant arborvitae is a hybrid, it does not come true from seed. Vegetative propagation via semi-hardwood stem cuttings is the standard commercial method and the most reliable approach for home gardeners. Take 6- to 8-inch cuttings from current-season lateral shoots in late fall to early winter. Strip the lower two inches of foliage, dip the cut end in a rooting hormone containing 0.3% IBA (indolebutyric acid), and insert cuttings into a well-drained rooting medium of perlite and peat (1:1). Maintain bottom heat around 70 °F and high humidity. For tips on maintaining the right environment during propagation, a humidity dome setup works well for arborvitae cuttings too. Expect rooting in 8 to 12 weeks, with success rates averaging 70 to 85%.

Seed Propagation

While green giant arborvitae occasionally produces small cones with viable seed, seedlings will not replicate the hybrid’s desirable traits uniformly. Seed propagation is not recommended for this cultivar.

Grafting

Some specialty nurseries graft green giant arborvitae onto rootstock of Thuja plicata or Thuja occidentalis for faster production. This method is typically beyond the scope of home gardening but can be useful for preserving particularly vigorous parent stock.

Care & Maintenance

Watering Schedule

During the first two years, water deeply once per week, providing approximately 1 to 1.5 inches of water each time. In hot summers or sandy soils, increase frequency to twice weekly. Established trees generally thrive on natural rainfall in zones 5 through 7 but may benefit from supplemental irrigation during extended droughts in zone 8. Always water at the base of the tree rather than overhead to minimize foliar fungal issues.

Fertilization

Feed green giant arborvitae once annually in early spring with a balanced, slow-release granular fertilizer (such as 10-10-10 or a formulation designed for evergreens) at a rate of 1 pound per inch of trunk diameter, spread evenly beneath the canopy drip line. Avoid fertilizing after midsummer, as late-season growth may not harden off before winter, increasing vulnerability to cold damage.

Pruning

One of the greatest advantages of green giant arborvitae is its naturally tidy, pyramidal shape, which rarely requires corrective pruning. If shaping is desired — for instance, to maintain a formal hedge at a specific height — prune in late spring to early summer, after the flush of new growth. Use hand shears or a hedge trimmer to remove no more than one-third of the current season’s growth. Avoid cutting into old wood (brown interior branches), as arborvitae does not regenerate from bare wood. For homeowners wondering how to grow green giant arborvitae as a managed hedge rather than a free-growing tree, consistent annual trimming starting when trees are young is the key.

Mulching and Winter Care

Maintain a 3- to 4-inch layer of organic mulch around the base year-round. In zone 5, wrapping newly planted trees with burlap during their first winter can prevent desiccation from cold winds. Protecting plants from frost is especially important during the first establishment year in colder zones. Once established, green giant arborvitae is remarkably winter hardy and requires no special protection.

Landscape Uses & Design

How to Grow Green Giant Arborvitae for Year-Round Privacy

The most popular use for green giant arborvitae is as a living privacy screen or windbreak. A single row planted at 5- to 6-foot spacing creates a solid wall of green within three to four years. For maximum wind protection, stagger plants in a double row with 8-foot spacing between rows and offset planting positions. The result is an impenetrable barrier that also reduces noise and filters dust.

Specimen and Accent Planting

As a standalone specimen, green giant arborvitae’s towering, symmetrical silhouette makes a bold vertical accent on large properties. Use it to frame driveways, anchor corners of buildings, or create a dramatic focal point at the end of a long sightline. The dark green foliage provides an excellent backdrop for flowering ornamentals — the bright blooms of hydrangeas or roses appear even more vivid against it.

Design Combinations

Pair green giant arborvitae with lower-growing broadleaf evergreens such as holly or boxwood for a layered screening effect. Ornamental grasses, perennial borders, and spring-blooming bulbs create attractive foreground plantings. The tree’s fine-textured foliage contrasts beautifully with the bold leaves of oakleaf hydrangea or the feathery plumes of astilbe.

Container Growing

Green giant arborvitae is not well suited to permanent container culture due to its large mature size and vigorous root system. While young plants can be temporarily grown in large containers (minimum 25 gallons), they will need to be transplanted into the ground within two to three years to sustain healthy growth.

Wildlife & Ecological Value

Green giant arborvitae provides meaningful ecological benefits in the residential landscape. Its dense branching structure offers excellent winter shelter and nesting sites for songbirds, including cardinals, sparrows, and juncos. Small mammals also use the low branches for cover during harsh weather. The tiny cones produced in fall contain seeds that are occasionally consumed by finches and chickadees.

Perhaps most notably, green giant arborvitae is highly resistant to deer browsing — a critical advantage in suburban and rural landscapes where white-tailed deer populations are high. While few plants are completely deer proof, this cultivar consistently ranks among the most unpalatable arborvitae selections. The aromatic oils in the foliage act as a natural deterrent.

As a non-native hybrid, green giant arborvitae does not support specialist native insects the way indigenous conifers do. However, its evergreen canopy contributes to year-round habitat structure, and its windbreak function reduces heat loss from buildings, indirectly benefiting energy conservation.

Common Problems & Solutions

Pests

Bagworms (Thyridopteryx ephemeraeformis): While green giant arborvitae shows greater resistance to bagworms than many arborvitae species, infestations can still occur. Inspect trees in late spring for small, spindle-shaped bags attached to branch tips. Hand-pick bags before June when caterpillars begin feeding, or apply Bacillus thuringiensis (Bt) for organic control.

Spider mites: Hot, dry conditions can promote spider mite infestations, evidenced by stippled, bronze-colored foliage. A strong blast of water from a garden hose dislodges mites. Horticultural oil or insecticidal soap applications are effective for persistent populations.

Diseases

Root rot (Phytophthora spp.): Poorly drained soils are the primary culprit. Symptoms include yellowing foliage, reduced growth, and eventual dieback. Prevention through proper site selection and avoiding overwatering is the best strategy — there is no effective chemical cure once root rot becomes established.

Tip blight (Kabatina thujae): This fungal disease causes browning of branch tips, primarily in late winter to early spring. Prune affected tips during dry weather and improve air circulation by thinning surrounding vegetation.

Environmental Stress

Winter burn: In exposed locations in zones 5 and 6, foliage on the windward side may desiccate and brown during harsh winters. Anti-desiccant sprays applied in late fall and windbreak protection for young trees minimize this issue.

Leaning from heavy snow or ice: Multiple-leadered specimens can splay under heavy snow loads. Prevent this by gently tying leaders together with soft twine in late fall, or select single-leader specimens at the nursery.

Varieties & Cultivars

While ‘Green Giant’ itself is the dominant cultivar in the marketplace, it’s helpful to understand how it compares to related arborvitae selections:

• Thuja plicata ‘Spring Grove’ (Spring Grove® Western Arborvitae): A patented selection of western red cedar with a similar growth habit to Green Giant but slightly narrower form. Hardy in zones 5–8. A strong alternative where a tighter columnar shape is preferred.
• Thuja occidentalis ‘Emerald’ (Emerald Green Arborvitae): A much smaller cultivar (10–15 feet tall) of eastern arborvitae, ideal for smaller properties. Hardy in zones 2–7. Slower growing and more prone to deer browse than Green Giant.
• Thuja occidentalis ‘Nigra’ (Dark American Arborvitae): Maintains dark green color through winter. Reaches 20–30 feet. Good choice for zones 2–7 where Green Giant may be too large.
• × Cuprocyparis leylandii (Leyland Cypress): Often compared to Green Giant as a fast-growing screen. Leyland cypress is more susceptible to Seiridium canker, bagworms, and root rot, making Green Giant generally the more reliable long-term choice in zones 6–8.
• Thuja plicata ‘Virescens’: A seed-propagated western red cedar selection with similar vigor. Slightly more variable in form than the clonally propagated Green Giant but often more affordable.

For most homeowners seeking a dependable, fast-growing privacy screen, comparing arborvitae varieties reveals that green giant excels in that role better than nearly any alternative.

Frequently Asked Questions

How fast does green giant arborvitae grow?

Green giant arborvitae is one of the fastest-growing evergreen screening trees available, adding 3 to 5 feet per year when young and planted in full sun with adequate moisture. Growth rate slows as the tree matures, but it can reach 40 to 60 feet in 15 to 20 years under favorable conditions.

How far apart should I plant green giant arborvitae for a privacy screen?

For a solid, continuous hedge, space trees 5 to 6 feet apart, measured center to center. For a more natural-looking screen where individual trees remain visible, space them 8 to 10 feet apart. Avoid planting closer than 5 feet, as crowding restricts airflow and increases disease risk.

Do green giant arborvitae turn brown in winter?

Unlike many arborvitae cultivars, green giant arborvitae retains its rich, dark green color throughout winter and does not bronze. Occasional browning of foliage on the windward side in very cold, exposed sites (zone 5) is possible due to winter desiccation but is generally temporary.

Are green giant arborvitae deer resistant?

Yes. Green giant arborvitae is widely regarded as one of the most deer-resistant arborvitae selections. The aromatic compounds in its foliage make it unappealing to deer. While no plant is completely deer proof, this cultivar rarely suffers significant browse damage even in areas with high deer populations.

How much sun does green giant arborvitae need?

Full sun (six or more hours of direct sunlight per day) is ideal and produces the densest, most attractive growth. The tree tolerates partial shade but will develop a more open, less symmetrical form in lower light conditions.

Can I grow green giant arborvitae in a container?

Only temporarily. Young trees can be maintained in large containers (25 gallons or more) for two to three years, but the tree’s vigorous growth and large mature size make permanent container culture impractical. Plan to transplant into the ground for long-term success.

What is the best time of year to plant green giant arborvitae?

Early fall is the best planting time in most regions, giving roots months to establish before summer heat. Early spring (before new growth begins) is the second-best option. In zone 5, spring planting is often preferred to maximize the first-year establishment period.

How do I know if my green giant arborvitae has root rot?

Symptoms include yellowing or browning foliage, wilting despite adequate moisture, reduced annual growth, and a soft or darkened root collar at the soil line. Root rot (Phytophthora) is almost always caused by waterlogged soil. Prevention through proper drainage is the only reliable control.

Should I fertilize my green giant arborvitae?

Yes, a once-annual application of balanced slow-release granular fertilizer (such as 10-10-10) in early spring promotes vigorous, healthy growth. Spread fertilizer beneath the canopy drip line and water it in thoroughly. Do not fertilize after July to prevent tender late-season growth that could be damaged by winter cold.

How close to a fence or property line can I plant green giant arborvitae?

Plant at least 6 to 8 feet from a fence or property line to allow room for the tree’s mature spread of 12 to 20 feet. Check local ordinances, as many municipalities have setback requirements for trees planted near property boundaries. Planning ahead avoids future conflicts and pruning headaches.

Can I keep green giant arborvitae short by pruning?

You can maintain a managed hedge height by trimming annually in late spring to early summer, removing no more than one-third of the current season’s growth. However, keeping a naturally 40- to 60-foot tree at, say, 10 feet requires persistent annual pruning. If you want a smaller arborvitae, consider Emerald Green (Thuja occidentalis ‘Emerald’), which matures at 10 to 15 feet.

Is green giant arborvitae toxic to pets?

The foliage of Thuja species contains thujone, an essential oil that can be mildly toxic to dogs and cats if ingested in large quantities. Symptoms may include vomiting, diarrhea, or lethargy. In practice, pets rarely consume enough foliage to cause serious issues, but keep an eye on puppies or animals known to chew on plants.

Sources & References

• USDA Plants Database — Thuja plicata (parent species)
• NC State Extension — Thuja ‘Green Giant’

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