• Thuja occidentalis Nigra is a cultivar, one of several in the Cupressaceae or Cypress Family. Thuja is Greek for juniper and occidentalis means western to denote its Western Hemisphere origins. Thuja occidentalis is an umbrella term for evergreen trees and shrubs including Eastern Arborvitae, Arborvitae, American Arborvitae and White Cedar. They have cultivars that are pyramidal, columnar or round and usually grace entryways, often serving as privacy screens standing in rows.
  
  

Nigra Profile

• Thuja occidentalis nigra is also known as dark American arborvitae. This evergreen blooms in the spring, preferring lots of sunshine with moist, rich and well-drained sandy loam to clay loam soil. It tolerates poor, rocky and dry soils too, as well as the effects of urban environments including heat, drought, humidity and pollution. It features ovate leaves that are dark green on the top with a lighter shade of green on the underside. A bushy tree well suited to cold areas, it is also a favorite of birds. It is a low maintenance tree, which adds to its attractiveness for foundation plantings.
  
  

Propagation

• The Ohio University Extension website points out that Thuja occidentalis is native to the northern half of eastern North America, and is well-established in American gardens. It is easy to propagate from cuttings, usually taken in the fall or early winter. For simple germination, place seeds in a moist medium like peat moss and refrigerate for 30 to 60 days before planting.
  
  

Use As Privacy Screens

• The Thuja occidentalis nigra or Nigra arborvitae is an ideal candidate for privacy screens, according to the Living Fences website. Consider placing it in areas that require height but have limitations in width. The Nigra arborvitae fits the bill because of its medium height of 20 to 25 feet and width at maturity of only about 4 feet 6 inches. Besides its advantageous size, this pyramidal tree also maintains its dark green foliage during the fall and winter months, as well as a manageable medium rate of growth.
  
  

Potential Problems

• If this tree has an Achilles heel, it may be that it does not thrive in the shade. Plant it in full sun for the best results. As a member of the Cypress family, dark American arborvitae is also susceptible to a number of potential diseases and pests, according to the Ohio State University website. Bagworms are an annual threat that can cause damage to the new leaves. Another possible problem is heartwood rot of the interior wood, which can deplete the tree's sources of energy and vitality as it ages. But these problems are rare and not common among these trees.