Thuja occidentalis 'Nigra,' also called Dark American Arborvitae, is a low-maintenance evergreen shrub that grows 15 to 30 feet tall and 5 to 10 feet wide. Thuja occidentalis is often grown for use as screens or hedges. The shrub grows in a pyramid shape with dark green leaves and the females produce cones. The Thuja occidentalis is native to eastern Canada and northeastern America, and it grows well in USDA Zones 3 through 7, so it's hardy down to about -35 degrees Fahrenheit.
Plant in full sunlight in well-drained but moist, loamy, deep soil. Thuja occidentalis shrubs love moisture.
Water your Thuja occidentalis once per week or more frequently during periods of drought or hot temperatures, especially when young. Mature, more established shrubs are more tolerant of dry conditions.
Shear the shrub to shape it and maintain its size. Prune the shrub lightly in early spring to get rid of tips with winter damage. Use hedging shears to make straight cuts on the sides and top of the Thuja occidentalis in late June or early July.
Protect the shrub against high winds, heavy snowfalls and ice. Plant your Thuja occidentalis in a protected area and cover it with blankets when an ice storm threatens. Remove heavy snow from the shrub to prevent branches from breaking.