The thuja green giant variety of arborvitae is a fast-growing evergreen that has become very popular for hedges and privacy screens. Young trees often grow more than 3 feet per year and readily adapt to soils ranging from clay to loam. Green giant thujas are very-low-maintenance plants and can reach heights of 50 to 60 feet if not pruned.
Plant your thujas in direct sunlight if possible, although these trees will tolerate partial shade as well. If planting for a hedge or screen the trees should be spaced 4 to 8 feet apart. Closer spacing will limit the height of mature trees.
Water the tree thoroughly when planted. In most areas rainfall is adequate for thujas, but hand watering is needed during dry spells. Keep the roots of young trees moist at all times before and during planting as they can quickly die if allowed to dry out completely.
Prune your green giants only if you are training them as a hedge. As landscape plants, these trees naturally maintain a narrow column-type shape without pruning or shaping.
Fertilize your trees sparingly if at all. Green giant thujas are hardy and can usually obtain sufficient nutrients from most types of soil. Do not fertilize thujas when planted or during the first year of growth to avoid potential root burn. If you decide to fertilize, use a balanced slow-release formula and apply in early spring and fall.
Apply a 3 to 4 inch layer of mulch around the base of the tree as far out as the drip line. Wood chips or shredded bark are good materials to use. Keep the mulch at least 6 inches away from the trunk to avoid rot problems. The mulch will help the keep water near to the roots and keep weeds and grass at bay.