The Green Giant Thuja (Thuja standishii x plicata 'Green Giant'), also known as the Green Giant arborvitae, is a hybrid of the Japanese arborvitae and western red cedar trees. This fast-growing, vigorous, low-maintenance tree reaches 50 to 60 feet tall and 12 to 20 feet wide, gaining up to 3 feet in height each year. The Green Giant is an evergreen with a pyramidal to conical shape and dense, deep green foliage that stands up easily to high winds, ice and snow. The Thuja Green Giant is a popular landscape tree, often planted in hedges, privacy screens, windbreaks and noise barriers. This tree grows best in USDA Hardiness zones 5 through 7, where summers aren't too hot and winter temperatures stay above minus 15 degrees F.
Water the Thuja Green Giant deeply to soak the soil around the root ball once each week during the first growing season. Water the Thuja once per week in subsequent growing seasons only during times of drought or prolonged dry spells.
Keep all weeds and grasses 2 to 3 feet away from the Thuja Green Giant, especially during the first one or two years after planting it. Hand-pull the weeds or spread a 3-inch-thick layer of mulch in a 2- to 3-foot-diameter circle on the ground around the tree.
Prune the Green Giant Thuja in late winter or early spring to remove any dead, diseased, broken or damaged growth. Shear the Thuja to keep it at a certain height if you're growing it as part of a privacy screen or hedge. No other regular pruning is necessary.
Feed the Thuja Green Giant once each year in early spring with a slow-release 10-10-10 NPK tree fertilizer, according to the dosage directions on the package.