Thuja Green Giant has become one of the most popular trees for creating a living screen. It’s no wonder: Green Giant is green throughout the year darker green in summer and may become a reddish brown or bronze slightly in winter; it is adaptable to most soil types; it is tolerant of light shade and of moderate drought; and it grows extremely fast.
Generally, arborvitaes are not an exceptionally fast-growing shrub, and insufficient watering slow them down even more. Green Giant is an exception, being one of the faster-growing arborvitaes. They grow at 3-5 feet per year to a maximum height of 50 to 60 feet at maturity . A row of rich Green Giants will quickly create a privacy screen that blocks the wind and snow, and the view.
Thuja ‘Green Giant’ is a large tree hybrid between the American native, western red cedar (Thuja plicata), and the Asian native, Japanese arborvitae (Thuja standishii). Thuja Green Giant evergreen trees grow faster and are said to stay bright green in winter than either parent. It is more cold hardy than the Japanese species and more tolerant of a lethal fungus (Didymascella thujina) than the American species.
Green Giant is not the only large tree in this family. An even taller species, T. plicata, can quickly grow to 50 to 75 feet high and 15 to 25 feet wide, earning it the common name "giant arborvitae." Other cultivars that can rightly be called giants are the fast-growing Zebrina, which can hit 30 feet in height (8 to 12 feet wide), and Hetz Wintergreen, a fast-growing variety that tops out at 30 feet high and 8 feet wide.
Green Giant is best grown in moist, fertile, well-drained soils in full sun to part shade. Tolerates somewhat wide range of soils and some dry conditions. Best in full sun, but generally appreciates some light afternoon shade in hot summer climates. For screens, plant trees 5-6’ apart. Plant trees further apart for other uses. They can be easily kept more compact by pruning for screens or hedges.
Wonderfully there are no serious insect or disease problems. Although bagworm and rots may occur. Watch for scale.