Emerald Green Eastern Arborvitae aka Smaragd Arborvitae Evergreen
Thuja occidentalis 
Botanical Reference: Thuja occidentalis
 
Synonym Advisory:
Originating in Denmark, the registered Cultivar Name for this Thuja occidentalis is'Smaragd'. It is marketed in the U.S. under the trade name Emerald Green™
 
Attribution from The American Conifer Society:
Thuja occidentalis 'Smaragd' / Emerald Green arborvitae
RECOMMENDED HARDINESS ZONES: (-20 to -30 F / -28.9 to -34.4 C) (Zone Range 3-7)
HORTICULTURAL STATUS: EstablishedORIGIN: Seedling SelectionCOLOR: Medium Green TRINOMIAL TYPE: CultivarGROWTH SHAPE: Narrow Upright or FastigiateGROWTH SIZE: Intermediate: 6 to 12 inches (15 – 30 cm) per year / 5 to 10 feet (1.5 – 3 m) after 10 years
 
Thuja occidentalis 'Smaragd' / Emerald Green arborvitae
Thuja occidentalis 'Smaragd' is a narrow upright selection of arborvitae with fine branchlets and glossy, emerald-green foliage that does not become bronze in winter. It is an extremely popular plant for use in hedgerows and borders. After 10 years in the landscape, a specimen will be considered mature at roughly 6 feet (2 m) tall and 18 inches (50 cm) wide, rate of growth approaching 1 foot (30 cm) per year.
 
Origin:
This cultivar originated as a seedling selected in 1950 by D. T. Poulsen Nursery, Kvistgaard Denmark. It is marketed in the U.S. under the trade name Emerald Green™, a designation that is generally rejected by nomenclature purists.