Green giant arborvitae (Thuja plicata) grows 50-60 feet in a pyramidal shape. This evergreen tree can spread 20-30 feet wide rapidly since it can grow more than 3 feet per year. Mature trees grow 1/2-inch-long cones that emerge green and then turn brown. This tree likes to grow in sun or partial shade and roots well in moist, good-draining soil.
Green giant arborvitae trees need to be protected from the wind when young. This tree is commonly grown as a screen, windbreak or single planting for a park or a large yard.
Place the seedling in the shade to prevent the tree from drying out in the sun. Do not leave the seedling in the sun since the temperature could literately cook the rootball in the container.
Measure the tree from the base of the trunk to the top. Measure the roots and prune away any excess roots. If the tree is 12 inches, then trim the roots to 12 inches. This will prevent a growth imbalance. Lay a board on the ground and spread out the roots. Trim the roots with a sharp knife using the piece of wood as a cutting board.
Dig a trench with a straight-edged shovel. Push the shovel down into the ground as deep as it will go. Push the shovel forward and backward to open the trench up. Remove the shovel from the hole.
Gather the roots together and push them down into the trench without letting the roots curl back upward. It is important to encourage the roots to grow downward and not towards the surface. This would cause the roots to grow shallowly along the surface weakening the anchoring of a mature tree.
Fill the trench with water and wait 10 minutes as it absorbs into the ground. Close the trench by firming the edges together with your feet. Some of the water will leak out of the trench. Make sure the green giant arborvitae seedling is standing up straight.
Space other green giant arborvitae seedlings 15 feet apart in a row. Give the seedlings plenty of room to grow to their mature size.