| General Description | Thuja occidentalis ‘Nigra’ (Black Cedar/Arborvitae) is a lovely cultivar of the straight species, Thuja occidentalis (Eastern White Arborvitae). It is a slow growing, tall, pyramidal-shaped conifer that maintains a rich, dark green foliage throughout all four seasons. It is slightly smaller than the straight species but maintains the same aromatic foliage. Thuja occidentalis ‘Nigra’ is native to Eastern North America in Canada and the United States of America. |
| ID Characteristic | The most effective way to identify Thuja occidentalis ‘Nigra’ is to observe the tall, columnar shape, dense, deep green, scale-like foliage and fan like structure. Another thing to observe is the aromatic foliage. |
| Shape | Thuja occidentalis ‘Nigra’ has a low canopy. They usually exhibit a tall, narrow, columnar form. Sometimes when young, the apical bud can be pinched to encourage a wider spread. There is a slight arch to the branching, and they are multi-stemmed. |
| Landscape | Thuja occidentalis ‘Nigra’ has many different landscape values. It can be used as a specimen, as an accent or as a massing plant. They can be used in small urban designs because they are slow growing and relatively pollution tolerant. They can also be used in larger landscapes because they do grow to be quite large. Black Arborvitae can be planted as a hedge, windscreen, or natural screen for privacy. Thuja occidentalis is used to create teas, in a medicinal fashion and crafted into essential oils. This cultivar can be included in such. Thuja occidentalis ‘Nigra’ is planted to favour it is rich, deep green, year-round colour. |
| Propagation | Thuja occidentalis ‘Nigra’ is propagated through cuttings from new growth during the current growing season. Remove some scale from the foliage at the end of the cutting and use 0.08% indole butyric acid rooting hormone to promote helpful root growth. Place in a peat moss, perlite mixture. Place in a protected highly humid propagation device allowing time for ventilation every one to two days. |
| Cultivation | Thuja occidentalis ‘Nigra’ is slow growing and prefers full sun to partial sun. It will tolerate areas that are more shaded, but this will subsequently affect the richness in the foliage colour. It prefers soil with an average moisture levels, and an above average moisture level, but will not tolerate extremely dry soil conditions. It is tolerant to both alkaline and acidic soil and is tolerant of mild urban pollution. |
| Pests | There are several pests and diseases that effect Black Arborvitae negatively. Some of which include Aphids, Canker, Tip-Blight, Leaf miner, Bagworms, Mealy Bugs, Scale and Spider mites. Spider mites and Bagworms are usually the most prominent issue seen with this species. Insecticides and early intervention are the best method to deal with these pests. Thuja occidentalis ‘Nigra’ is also known to be susceptible to Winter Burn. Branches and stems can be damaged if heavy snow and ice is piled on them during the winter months. |
| Habitat | Thuja occidentalis ‘Nigra’ is of a horticultural origin. They have many uses in the landscape such as hedges, windscreens, accent, or specimen trees. They tolerant very wet, swampy soils and can be planted in such conditions. |
| Bark/Stem Description | Thuja occidentalis ‘Nigra’ exhibits a reddish-brown bark, that is rough in texture and appear to be exfoliating. New growth is green which transforms into a reddish-brown with maturity. |
| Flower/Leaf Bud Description | Flower and leaf buds on Thuja occidentalis ‘Nigra’ are insignificant and very small. |
| Leaf Description | Foliage on the Black Cedar is scale-like, small, and flat. This creates a fan shaped appearance throughout branches. Foliage is aromatic and maintains a deep green complexion year-round. |
| Flower Description | Flowers on Thuja occidentals ‘Nigra’ are not showy and lack ornamental value. They are monecious, terminal and contain one solitary flower located at the tip of the foliage. They are tiny, estimated 3 mm to 5 mm in size. |
| Fruit Description | Cones on Thuja occidentalis ‘Nigra’ have very little ornamental value. They are slender, oblong, 6-8 mm, and grow in heavy clusters along the branches. They start as a green-yellow colour and mature to light brown. |
| Colour Description | The most prominent colour feature on Thuja occidentalis ‘Nigra’ is the dark, deep, rich green colour that is maintained by the plant all year. The bark of this tree is reddish-brown in maturity and new growth is a yellow-green colour. Cones are yellow in infancy and turn light brown in maturity. Flowers are rare and insignificant |
| Texture Description | This is a course, dense plant with a flat, fan-like shape. The density of the canopy is maintained through all months of the year. |