Thuja is a genus consisting of six species of coniferous, evergreen trees native to East Asia and North America. The "Green Giant" Arborvitae (Thuja standishii × plicata) variety is an especially fast-growing hybrid cultivar. It is a cross hybrid between the Western Redcedar and Japanese arborvitae. Native to Europe, the D.T. Poulsen nursery of Copenhagen, Denmark chose and introduced the "Green Giant" to the U.S. National Arboretum in 1967.
Beloved for its lush aesthetic and ability to propagate, it was distributed widely and confused with a different arborvitae from the same source known as T. occidentalis "Giganteoides." The clone identity was resolved by Susan Martin, USNA, Kim Trip, New York Botanic Garden, and Robert Marquard, Holden Arboretum by means of thorough nursery inspections, record searches, and "isozyme analysis." Then the name Thuja "Green Giant" was selected.
Now, it is available at many wholesome nurseries, at retail sources, and by mail-order. Grown as an ideal substitute for Leland cypress in the southeastern United States, this large, needled tree is easy to grow and generally free of pests and disease. Mature trees reach up to 40 to 60 feet tall, growing densely, narrowly, and in a pyramidal habit. Leaves are small, glossy, and scale-like, opposite and arranged in rows of four, overlapping, creating flat sprays akin to the shape of fans. The bark is dark brown and shaggy. Small, upright seed cones emerge as green and then mature to brown, up to a half-inch long. Unlike some other evergreens, its rich, dense, green foliage does not yellow or brown in winter and only slightly bronzes or darkens. Coexisting with birds and small animals, this tree creates places for nesting and flower buds, as well as seeds and foliage for food. This plant is toxic to grazing animals like cattle, sheep, and horses.
|Common Name||Green Giant Arborvitae|
|Botanical Name||Thuja standishii x plicata ‘Green Giant’|
|Plant Type||Needled evergreen|
|Mature Size||40 to 60 ft. tall, 12 to 18 ft. wide|
|Sun Exposure||Full sun to part shade|
|Soil Type||Fertile, well-drained clay or loamy|
|Soil pH||Acidic, Neutral, or Alkaline|
|Hardiness Zones||5 to 8, USDA|
Green Giant Arborvitae Care
Plant trees 5 to 6 feet apart to establish a privacy hedge or security screen. For other use, plant further apart in small groups or as specimens. Establish groups of them in lawns or in the background of landscapes. In addition to defining property lines, shielding noise and rough wind, the "Green Giant" Arborvitae also emits a wonderful fragrance. Keep in mind that the tree is susceptible to wind damage and can uproot easily.
"Green Giant" Arborvitae prefers full sun. It will tolerate part shade and actually thrives in some light afternoon shade in hot summer climates.
Able to grow in a range soils such as poor soil and clay, it does best in moist, fertile, well-drained loams. Avoid wet soil that does not drain well and exposure to spray or salt.
Water and Fertilizer
You should not fertilize the tree in the first year after planting. For the early years after that, enrich the soil with plenty of water and balanced fertilizer; this will promote continuous, vigorous growth. Then, as with more arborvitae, it will not need much or any fertilizer.
Propagate the tree from stem cuttings from July through March. Root cuttings under mist with bottom heat (3000–8000 ppm IBA).
Pruning Green Giant Arborvitae
Covered in dense, dark, evergreen foliage from the ground up, the "Green Giant" arborvitae needs little to no pruning or shearing. Growing elegantly and consistently, it only needs to be pruned if necessary or for aesthetic reasons. Shear into a desired shape and size, and maintain it throughout the warmer months.
Common Pests & Plant Diseases
Fortunately, this variety is more resistant to deer than most arborvitae and it has no major insect or disease issues. Keep an eye out for scale, rots, and bagworm in poorly drained soils.
Are Giant Green Arborvitaes easy to care for?
Yes, they are. Giant Green Arborvitaes are tolerant of drought, heat, humidity, cold, wind, ice and snow damage, and to many pests including deer.
How fast do Green Giant Arborvitaes grow?
They grow very fast. This variety is actually one of the fastest-growing conifers. Growing 3 to 5 feet every year, a mature tree can reach as much as 50 feet tall and 5 feet wide in a span of 10 years.
How long can Giant Green Arborvitae live?
When cared for well, Thuja Green Giants live for up to 40 years.
What's the difference between Thuja Green Giants and Emerald Green Thuja?
While "Green Giant" Thujas are known for being rather large and fast-growing, "Emerald Green" Thujas only grow 8 to 12 feet tall and 3 to 4 feet wide. They are better suited for smaller landscapes, will fit easier into tighter spaces such as around a driveway, and will even grow in containers. Another difference is their tolerance levels to temperature. "Green Giant" arborvitaes tolerate some snow and ice and temperatures down to -20 degrees Fahrenheit, but "Emerald Green" arborvitaes are much more cold resistant. Therefore, Thuja "Green Giants" will thrive in dry, southern areas where some other evergreens like the "Emerald Greens" may not.
“Thuja Standishii x Plicata ‘Green Giant’ / Green Giant Hybrid Arborvitae | Conifer Trinomial.” American Conifer Society, 11 Mar. 2020, conifersociety.org/conifers/thuja-standishii-x-plicata-green-giant
“Thuja ‘Green Giant.’” The U.S. National Arboretum, Nov. 1999,
“Thuja ‘Green Giant’ (Green Giant Arborvitae) | North Carolina Extension Gardener Plant Toolbox.” North Carolina Extension Gardener Plant Toolbox, 2011, plants.ces.ncsu.edu/plants/thuja-green-giant.
“Green Giant Arborvitae Tree on the Tree Guide at Arborday.Org.” Arbor Day, www.arborday.org/trees/treeGuide/TreeDetail.cfm?ItemID=779.
“Green Giant Arborvitae Tree on the Tree Guide at Arborday.Org.” Arbor Day, 2021, www.arborday.org/trees/treeGuide/TreeDetail.cfm?ItemID=779.
Park Seed Co. “Green Giant Arborvitae.” Jackson and Perkins, 24 May 2014, parkseed.com/green-giant-arborvitae/p/v1755.