Thuja occidentalis 'Nigra' / black arborvitae

Thuja occidentalis 'Nigra' is a compact, conical selection of eastern arborvitae with exceptionally dark-green foliage that retains good green color in the winter in cold climates. After 10 years of growth, a mature specimen will measure 6 feet (2 m) tall and 3 feet (1 m) wide, an annual growth rate of 6 to 8 inches (15 - 20 cm).

This is an rather old cultivar in the nursery trade that unfortunately is of unknown origin. It is thought to have originated in the USA in the 1930s. L. H. Bailey formally described it in his 1933 book, Cultivated Conifers in North America.

An attractive grouping of Thuja occidentalis 'Nigra' in an arboretum setting.
Photo by Jesse Saylor
Thuja occidentalis 'Nigra' — a closeup of foliage detail.
Photo by James H. Schutte


Carolyn Wenstrup

We planted a Thuja 'Nigra' (arborvitae) in the spring. Now that it is fall it has a lot of brown ... is that normal?

David Olszyk

Hi Carolyn, it's perfectly normal for this species to shed up to 25% of its internal foliage every fall. In your case, it was almost certainly amplified by the fact that you planted in spring (that's a really bad time to be planting trees in most parts of the country).