Green Giant arborvitae is a cultivar of the thuja species and is a large, fast-growing evergreen shrub with a tall, upright, almost columnar profile. Hardy in USDA Hardiness Zones 5 through 7a, Green Giant is tolerant of most soil conditions and reaches up to 60 feet in height at peak maturity, according to the United States National Arboretum. Green Giant is used as a specimen ornamental or planted en masse for screening and framing of views.
Prepare a planting bed for your Green Giant by tilling up the soil out to 4 feet from where the thuja trunk will be placed. Use a shovel, fork, spade or tiller to loosen and lighten the soil, break up clumps and remove stones. Till to a depth of at least a foot.
Amend the planting soil with organic material to support the evergreen nutritionally over time. Mix in generous amounts of well-aged livestock manure, sphagnum peat moss and compost into the loosened soil.
Excavate a hole in the amended soil that is twice the diameter of the root ball and just as deep. Place your thuja in the hole, adding soil as needed under the root ball to bring the top of the root mass level with the surrounding soil.
Turn the tree so that its most pleasing aspect is facing you. Step back 10 feet or more to see that the tree is straight in the hole and perpendicular to the soil, if the soil is flat. Look at it from several angles or vantage points if need be.
Backfill the excavated and amended soil around the root ball halfway up and tamp down lightly with your shoe heel or hands to secure the tree upright in the soil. Fill in the remaining soil and tamp again lightly.
Create a watering berm with the remaining soil just outside the drip line of the thuja. Fill the interior ring of the berm with water and allow it to percolate down into the soil entirely before refilling. Keep the soil evenly moist until the tree is well established in the soil. Knock down the berm after a few weeks, spreading out the material as mulch under the tree.