How to Grow American Arborvitae Green Giant

American Arborvitae Green Giant

Thuja occidentalis 'Green Giant'

tree

Green Giant is a fast-growing evergreen conifer cultivar of American arborvitae, prized for its narrow pyramidal form and vibrant emerald foliage year-round. It can reach 40-60 feet tall but only 12-20 feet wide, making it ideal for screening, windbreaks, and privacy hedges. This hardy cultivar maintains its color in winter and resists common arborvitae diseases better than many other varieties.

Growing Conditions

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Sun: Full sun to partial shade; prefers 6+ hours of direct sun daily for best color and density

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Water: Moderate water needs; keep soil consistently moist but not waterlogged during the first 2 years. Established trees are drought-tolerant but benefit from occasional deep watering during dry spells. Reduce watering in late summer to harden off growth before winter.

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Spacing: 120-180 inches

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Days to maturity: 3-5 years to reach functional screening height; 15-20 years to mature size

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Planting depth: Plant at same depth as root ball; top of root ball should be level with ground

Soil

Type: Well-draining loamy or sandy soil; tolerates clay

pH: 5.5-7.5

Amendments:

Compost or peat moss at planting Mulch layer for moisture retention Perlite or sand if drainage is poor

Growing Zones

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Thrives in zones 2-8, with best performance in zones 3-7

2a 2b 3a 3b 4a 4b 5a 5b 6a 6b 7a 7b 8a

Growth Stages

Establishment

Year 1

Young plant with compact pyramidal form, bright green foliage, establishing root system

Keep soil consistently moist but not soggy. Apply 2-3 inches of mulch around base, keeping it away from trunk. Protect from strong winter winds with burlap if necessary. Avoid fertilizing first year.

Early Growth

Years 2-3

Rapid vertical growth begins, reaching 2-3 feet per year; foliage becomes denser

Water deeply 1-2 times weekly if rainfall is insufficient. Apply balanced slow-release fertilizer in spring. Stake if in exposed windy location. Light pruning can shape form if needed.

Vigorous Growth Phase

Years 3-8

Peak growth rate of 2-3 feet annually; columnar form becomes pronounced; dense feathery foliage

Maintain consistent moisture especially during hot summers. Reduce fertilizer to annual spring application. Can prune sides lightly to maintain narrower profile if desired. Watch for spider mites in hot, dry conditions.

Mature Development

Years 8+

Growth slows; reaches desired height of 40-60 feet; maintains dense, vibrant green color year-round

Water during prolonged drought. Minimal pruning needed except to remove dead/damaged branches. Monitor for scale insects and bagworms. Mulch maintained to conserve moisture.

Companion Planting

Plan your garden →

Plant with:

Eastern Red Cedar Boxwood Yew Serviceberry Juniper Hosta Shade-tolerant groundcovers

Avoid planting near:

Black walnut trees (allelopathic toxicity) Salt-sensitive plants if used near roads treated with de-icing salts

Common Pests

Remove bags by hand in winter; spray with Bt (Bacillus thuringiensis) in late spring when larvae hatch
Increase humidity with foliar misting; spray with insecticidal soap or neem oil; avoid stressing trees with drought
Prune out infested tips; spray with insecticide in early spring before adults emerge
Spray with horticultural oil in dormant season; use insecticidal soap during growing season
Prune out infected branches; improve drainage and avoid wounding trees; ensure adequate sunlight and air circulation

Uses

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Privacy Screen & Windbreak

Household

Green Giant is widely used as a fast-growing privacy hedge and windbreak due to its narrow columnar form and rapid growth rate of 2-3 feet per year. Its dense foliage effectively blocks sight lines and reduces wind velocity while requiring minimal space. [source]

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Ornamental Landscaping

Craft

The vibrant emerald-green foliage and elegant pyramidal silhouette make Green Giant an attractive focal point or backdrop in formal and naturalistic landscapes. It maintains excellent winter color, distinguishing it from many deciduous conifers. [source]

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Wildlife Shelter & Nesting

Wildlife

The dense branching structure provides excellent shelter and nesting habitat for birds and small wildlife. Arborvitae foliage is browsed by deer in winter, and seeds provide food for songbirds. [source]

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Sound Reduction & Environmental Buffer

Household

Dense coniferous hedges significantly reduce noise pollution from roads and neighbors. Green Giant's rapid growth and year-round foliage make it more effective than deciduous alternatives for this purpose. [source]

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Traditional Herbal Uses

Medicinal

Historically, arborvitae foliage and wood have been used in traditional medicine for respiratory support and immune function. The essential oils contain thujone, though internal use should only be under professional guidance. [source]

This is not medical advice. LizPlants is not a medical resource. Always consult a qualified healthcare professional before using plants medicinally.

Harvest Tips

Not typically harvested like other plants. For ornamental purposes, dead or damaged branches can be pruned out any time. Light formative pruning best done in early spring or late winter before new growth begins. Avoid heavy pruning which can cause browning.

Fun Facts

🌱 Green Giant was developed in Denmark and is sometimes called 'Smaragd' (Emerald) in Europe; it was selected for superior disease resistance and growth rate compared to standard American arborvitae.
🌱 Despite its common name, Green Giant is actually a hybrid between Eastern arborvitae (Thuja occidentalis) and Western arborvitae (Thuja plicata), combining the best cold-hardiness and disease resistance of both species.
🌱 A mature Green Giant can grow over 60 feet tall in ideal conditions while remaining only 12-20 feet wide—making it one of the narrowest columnar evergreens and ideal for small-footprint screening applications.

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