Green Giant Arborvitae (Thuja standishii x plicata ‘Green Giant’)

Thuja is a prominent genus which encompasses six distinct species of evergreen trees originally found in regions of East Asia and North America. A particularly noteworthy variety within this genus is the “Green Giant” Arborvitae (Thuja standishii × plicata), a vigorous hybrid cultivar with rapid growth attributes. This popular tree variant is a fusion of the Japanese arborvitae and the Western Redcedar. Interestingly, this cultivar’s journey began in Europe, where the D.T. Poulsen nursery based in Copenhagen, Denmark recognized its potential and subsequently introduced it to the U.S. National Arboretum in the late 1960s.

In the beginning, the “Green Giant” variety enjoyed immense popularity due to its pleasing appearance and effortless propagation process. However, it experienced a case of mistaken identity, as it was often mixed up with another arborvitae variant, T. occidentalis “Giganteoides,” originating from the same nursery. Thankfully, this confusion was clarified through meticulous nursery investigations and detailed record analyses carried out by experts like Susan Martin from USNA, Kim Trip from the New York Botanic Garden, and Robert Marquard from the Holden Arboretum. Their collaborative effort which also included “isozyme analysis,” culminated in the official naming of this variety as the Thuja “Green Giant.”

Currently, the Thuja “Green Giant” is a widely accessible option for gardening enthusiasts, being available at numerous nurseries, retail outlets, and even through mail orders. Its growth characteristics make it a preferred alternative to the Leland cypress, especially in the southeastern regions of the United States. This robust tree not only grows quickly but is also fairly resistant to most pests and diseases, making it a relatively low-maintenance choice for gardeners.

As a mature tree, it boasts a grand stature, reaching heights between 40 to 60 feet, with a natural tendency to grow in a narrow, pyramidal fashion. Gardeners will appreciate the small, glossy, and scale-like leaves that arrange themselves in quadruple rows, forming a flat, fan-like spray. The dark brown, shaggy bark adds a rustic charm to its appearance. It also features small seed cones that transition from green to brown as they mature, measuring up to half an inch in length. One of its standout features is its evergreen nature, maintaining a vibrant green foliage that does not succumb to yellowing or browning even in the cold winter months, though a slight bronzing or darkening may occur.

Moreover, this tree serves as a haven for wildlife, offering shelter and nesting spaces for birds and small creatures. It provides an array of food sources including flower buds and seeds. However, it is worth noting that the plant contains toxins that are harmful to grazing animals such as cattle, sheep, and horses, thus caution is advised in areas where these animals are present.

Green Giant Arborvitae Care

The Green Giant Arborvitae makes an ideal choice for those looking to establish a natural privacy barrier or windbreak in their gardens or yards. Planting them at intervals of 5 to 6 feet will form a secure screen or hedge, promoting privacy and reducing noise and harsh winds. You might also consider arranging them in small clusters or as stand-alone specimens for different aesthetic effects, such as on lawns or as a backdrop in landscapes. Apart from serving as a visual and physical barrier, the Green Giant Arborvitae is known for its pleasant fragrance. However, be cautious as the tree has a tendency to get uprooted easily in strong winds, thus it may be vulnerable to wind damage.

Light

The Green Giant Arborvitae thrives best under full sun exposure but doesn’t shy away from partial shade, especially in regions experiencing hot summers. In fact, it can benefit from a bit of afternoon shade during the warmer months.

Soil

When it comes to soil preferences, this tree is quite adaptable, capable of growing in a variety of soil types including those less fertile or clayey. However, for optimum growth, planting it in well-drained, moist, and fertile loamy soil is recommended. Make an effort to steer clear from areas with poor drainage and high salinity or spray exposure to prevent potential root issues.

Water and Fertilizer

During its initial year, refrain from fertilizing the Green Giant Arborvitae to allow it to establish naturally. In the subsequent early years, encourage a steady growth by providing ample water and incorporating a balanced fertilizer into the soil regime. As it matures, its dependency on fertilizers tends to diminish, requiring little to no additional nutrients.

Propagation

To propagate this tree, use stem cuttings taken anytime from July to March. Ensure a successful root development by placing the cuttings under mist settings complemented with bottom heating, utilizing a rooting hormone concentration ranging from 3000 to 8000 ppm IBA.

Pruning Green Giant Arborvitae

The Green Giant Arborvitae is naturally endowed with lush, dark foliage extending from its base to the top, eliminating the frequent need for pruning or shearing. However, if you prefer a specific shape or size, occasional pruning for aesthetic maintenance is perfectly fine, preferably during the warmer seasons.

Common Pests & Plant Diseases

One of the positive aspects of opting for the Green Giant Arborvitae is its increased resistance to deer, a common pest to many garden plants. Moreover, it generally remains unaffected by major insect infestations or diseases. Nonetheless, maintaining vigilance for potential threats like scale insects, root rots, and bagworms, particularly in soils with poor drainage, can aid in its healthy growth.