Taxonomy, Botanical Type for 'Emerald Green' Arborvitae Trees
Plant taxonomy classifies arborvitae under the botanical name, Thuja occidentalis. 'Emerald Green' is one of its cultivars. You will also see 'Smaragd' listed as the cultivar name. That is because the plant was originally developed in Denmark (Smaragd translates from the Danish as "Emerald").
The common name for these conifers is often misspelled, "arbor vitae" (technically, when spelled as two words, it is an anatomical term, being part of the cerebellum, not a tree). The term is Latin and means "tree of life," due to the alleged medicinal value of its resin, as is discussed in this article on the 'North Pole' cultivar. Oddly, this is a case in which a plant's common name and scientific name, while different, are both Latin.
'Emerald Green' arborvitae is an evergreen in the Cypress family (Cupressaceae). Although some might say they are, technically, tall shrubs, they are commonly referred to as "trees," which is how they are treated here.
Growing Conditions, Characteristics, Growth Rate
'Emerald Green' arborvitae usually reaches just 12-14 feet tall, with a spread of 3-4 feet. It grows in a pyramidal form. Its foliage comes in flat sprays and, if you look closely, the needles appear covered in scales. It is not the fastest grower in its group (that would be the 'Green Giant' cultivar), but the trade-off is that the size of this slow grower is often just about right for a privacy hedge.
Its cultivar name is well-deserved. Whereas the leaves of many types of arborvitae take on a bronze color in winter, this kind's foliage is more likely to remain a nice green color.
Plant Care (When to Prune), Planting Zones
If the typical dimensions for these plants are still too big for your needs, they can be pruned in early spring (before any new growth comes out) to a size with which you are more comfortable. Since this tree is not drought-tolerant, water well during hot summers and mulch generously to hold in some of that water.
'Emerald Green' arborvitae should be grown in USDA plant hardiness zones 2-7. Thuja is a genus native to North America. As you can see from the growing zones listed for it, the genus is extremely cold-hardy. It is encountered frequently by hikers in the forests of chilly northern Maine. In fact, a favorite small public garden, located in the Bar Harbor, Maine area, is called "Thuja Gardens"; the surrounding woods are filled with wild Thuja.
Uses in Landscaping, Problems for 'Emerald Green' Arborvitae Trees
A slim tree of medium height, 'Emerald Green' arborvitae is often planted in a row -- as a decorative hedge for a border planting, windbreak or privacy screen. It is big enough to act as a screen without being so big as to be overwhelming, unlike the fast-growing 'Green Giant,' which grows to be 50-60 feet tall with a a width of 12-20 feet.
Because it is evergreen, its usefulness in any of these capacities extends throughout the year in the North. Occasionally, the tree is also used as a specimen, although it does not meet the typical standards of beauty for such a use. Consider it, rather, a tree that can serve a practical purpose: namely, to furnish privacy in the yard. Indeed, it is because people are finding it one of the best evergreens for a privacy screen that the popularity of this plant has soared.
To create a dense privacy hedge, proper spacing is important. The recommendation is to space the plants 2–3 feet apart for such a hedge. But there is one potential drawback in such spacing: crowding can invite Keithia or Seiridium blight, because the inner leaves are subjected to insufficient air flow. A 4-foot spacing represents a compromise: a little less privacy, but potentially better plant health. Another potential problem for the plant is being eaten by deer pests; if you have deer where you live, consider planting deer-resistant trees, instead.
Leyland Cypress vs. 'Emerald Green' Arborvitae Trees
Its cold hardiness makes 'Emerald Green' arborvitae a solid choice for Northern landscapers, who might otherwise use Leyland cypress, a favorite in zone 6 and higher (Leyland is commonly grown in the South). 'Emerald Green' arborvitae might also be the choice over Leyland cypress in cases where a tall tree would be inappropriate. Whereas some cultivars of the latter reach at least 60 feet at maturity, 'Emerald Green' arborvitae usually reaches just 12-14 feet in height. These differences notwithstanding, the two trees have a similar look and are both popular, particularly as "living wall" privacy screens.