Green Giant Arborvitae (Thuja standishii x plicata) is a fast-growing evergreen tree that belongs to the Cupressaceae family, which includes cypresses and cedars. It is a hybrid between two species—Thuja standishii, native to Japan, and Thuja plicata, known as the Western redcedar, native to the Pacific Northwest of North America. This interspecific cross combines the strength, resilience, and aesthetic qualities of both parents, making Green Giant Arborvitae a widely favored ornamental tree in landscapes across the United States.
The hybrid was first developed in Denmark during the early 20th century and introduced to the United States by the U.S. National Arboretum in the 1990s. It quickly gained popularity as an ideal replacement for Leyland cypress and other fast-growing evergreens that were prone to diseases or pest issues. Due to its excellent adaptability, attractive appearance, and resistance to many common landscape problems, Green Giant Arborvitae has become a standard choice for privacy screens and windbreaks.
This tree is easily recognized by its dense, pyramidal shape and deep green, scale-like foliage that stays vibrant year-round. The foliage grows in flattened sprays and emits a pleasant, cedar-like scent when crushed. The bark is reddish-brown and fibrous, often peeling in vertical strips. Green Giant Arborvitae maintains a uniform shape without much pruning, and its full, lush growth habit makes it ideal for blocking wind, noise, or unwanted views.
One of the most impressive traits of Green Giant Arborvitae is its rapid growth rate, which can exceed 3 feet per year under favorable conditions. It can reach mature heights of 40 to 60 feet and a width of 12 to 18 feet, forming a towering, stately screen. In terms of lifespan, these trees can live for 40 to 60 years or more when properly cared for, making them a long-term investment in residential and commercial landscapes.
The tree is widely distributed throughout temperate regions of the United States, especially in areas with moderate rainfall and well-drained soils. It adapts well to various soil types, including sandy, loamy, and even clay-heavy soils. While it prefers full sun, it can tolerate some partial shade and is relatively drought-tolerant once established. Its resistance to many pests and diseases also contributes to its broad appeal.
Green Giant Arborvitae thrives in USDA Hardiness Zones 5 to 8, which covers a significant portion of the eastern and central United States, parts of the West Coast, and areas with mild winters and warm summers. It is not well suited to extremely cold climates (zones 3–4) or very hot, arid regions (zones 9–10), where its growth may be stunted or stressed.
Other notable facts about this tree include its high resistance to deer browsing, a feature that sets it apart from many other arborvitaes. It is also relatively low-maintenance, requiring little pruning, fertilizing, or watering once established. The dense foliage provides excellent habitat for birds and wildlife, enhancing the ecological value of any landscape where it’s planted.
Landscape uses of Green Giant Arborvitae include:
- Privacy screens and living fences
- Tall hedges for property boundaries
- Windbreaks to protect homes and gardens
- Noise barriers along roads or near urban development
- Specimen planting for vertical interest
- Evergreen backdrops for gardens and mixed borders
- Screening for air conditioning units, compost bins, or utility areas
- Natural enclosures for outdoor spaces like patios or pools
Landscape uses of Green Giant Arborvitae include:
- Privacy screens and hedges
- Windbreaks or shelterbelts
- Noise barriers along roadsides or property boundaries
- Standalone specimen tree for ornamental planting
- Backdrops for perennial borders or garden features
- Framing entrances or driveways
- Foundation plantings in large landscapes
- Evergreen groupings in park or urban settings
Common problems associated with growing Giant Arborvitae (Thuja standishii x plicata)
Root rot
– Caused by poorly drained or consistently soggy soil
– Leads to yellowing foliage and dieback
Bagworms
– Caterpillars that create protective silk bags on branches
– Feed on foliage, causing thinning and browning
Spider mites
– Tiny pests that suck sap from the foliage
– Lead to stippled, yellowed leaves and webbing during hot, dry conditions
Drought stress
– Can occur during prolonged dry spells, especially in the first few years
– Results in browning or dropping of inner foliage
Wind damage
– Strong winds can dry out or break branches, especially in exposed sites
– May cause leaning if trees aren’t well-established
Snow and ice accumulation
– Heavy snow or ice can bend or break branches due to the dense, upright growth
– Often leads to permanent deformity if not corrected
Improper spacing
– Planting too close together limits airflow and increases disease risk
– Can also cause uneven growth and competition for nutrients
Nutrient deficiencies
– Poor soil may cause pale or stunted foliage if not amended
– Usually corrected with balanced fertilization
Transplant shock
– Common in newly planted trees, especially in hot or dry weather
– Causes temporary wilting or browning
Over-pruning or topping
– Can damage natural shape and cause stress
– Recovery is slow due to limited regrowth from old wood
Cultivation of Green Giant Arborvitae (Thuja standishii x plicata)
landscapes.
- Site Selection: Choose a location with full sun (6+ hours daily) to partial shade for best growth. Green Giant thrives in well-drained soils but tolerates clay, loam, or sandy soils. Avoid low-lying areas prone to waterlogging, as excessive moisture can cause root rot.
- Soil Preparation: Test soil pH, aiming for slightly acidic to neutral (6.0–7.5). Amend heavy clay with organic matter (compost or peat moss) to improve drainage. Loosen soil to a depth of 12–18 inches to encourage root establishment.
- Planting Time: Plant in spring or early fall to allow roots to establish before extreme heat or cold. In warmer climates (Zones 7–8), fall planting is ideal; in cooler regions (Zone 5), spring is better to avoid winter stress.
- Spacing: Space trees 5–10 feet apart for hedges or privacy screens, depending on desired density, or 12–15 feet for individual specimens to accommodate their 12–20-foot mature spread. Closer spacing creates a tighter hedge but may limit air circulation.
- Planting Process: Dig a hole twice as wide and as deep as the root ball. Place the tree so the root crown is level with the soil surface. Backfill with native soil mixed with compost, tamp gently, and water thoroughly to eliminate air pockets.
- Watering: Provide 1–2 inches of water weekly during the first two years, especially in dry periods. Once established, Green Giant is drought-tolerant but benefits from occasional deep watering during prolonged droughts. Avoid overwatering to prevent root issues.
- Mulching: Apply a 2–3-inch layer of organic mulch (bark, wood chips, or straw) around the base, keeping it 2 inches from the trunk to prevent rot. Mulch conserves moisture, regulates soil temperature, and reduces weeds.
- Fertilization: Fertilize in early spring with a balanced, slow-release fertilizer (e.g., 10-10-10) to promote growth. Avoid over-fertilizing, which can burn foliage. Established trees typically need minimal fertilization unless soil tests show nutrient deficiencies.
- Pruning: Prune lightly in spring or early summer to shape hedges or remove dead branches. Green Giant naturally maintains a conical shape, so heavy pruning is rarely needed. Use clean, sharp shears to avoid disease transmission.
- Winter Care: In colder zones, protect young trees from winter burn by wrapping them in burlap or applying anti-desiccant sprays. Water deeply before the ground freezes to ensure hydration through winter. Shake off heavy snow to prevent branch breakage.
- Propagation: Green Giant is typically propagated via cuttings, as it’s a hybrid and doesn’t produce viable seeds. Take semi-hardwood cuttings in late summer, treat with rooting hormone, and plant in a moist, well-drained medium under controlled conditions.