Arborvitae is definitively not a true cedar, despite common names used in landscaping. These two popular evergreens belong to entirely separate plant families, resulting in distinct characteristics. While both offer year-round green foliage, their physical structure, growth habits, and eventual sizes differ significantly. Understanding these differences requires moving beyond simple naming conventions to recognize two unique types of coniferous trees.
The Source of the Taxonomic Confusion
The widespread confusion between these trees stems from a clash between scientific classification and common naming traditions. A plant’s true identity is defined by its genus and family, determined by shared evolutionary history and distinct physical structures. Common names, however, are often based on superficial similarities or historical uses, leading to frequent misidentification.
Arborvitae plants are classified under the genus Thuja, placing them within the Cypress family (Cupressaceae). This family includes other well-known conifers like junipers. Many Thuja species, such as Thuja occidentalis, are informally called “Northern White Cedar” or “Eastern White Cedar,” which contributes directly to the public confusion.
True Cedars belong to the genus Cedrus, which is part of the Pine family (Pinaceae). This family also encompasses pines, firs, and spruces. The Cedrus genus is native to the Mediterranean and Himalayan regions, while Thuja species originate in North America and East Asia.
The use of “cedar” in a common name usually signifies aromatic wood or a similarity in appearance, but it does not imply a genetic relationship. Other unrelated trees, like the Western Red Cedar (Thuja plicata), are also frequently mislabeled. The distinction between the Thuja and Cedrus genera is the scientific basis for recognizing two separate groups of plants.
Key Identifying Features of Arborvitae
The defining feature of Arborvitae (Thuja species) is their distinctive scale-like foliage, which grows in flattened, fan-shaped sprays. These tiny, overlapping leaves are tightly pressed against the branchlets, creating a dense, two-dimensional appearance. Crushing the foliage often releases a pungent, citrusy aroma.
The female seed cones are small and inconspicuous, typically measuring only one-third to one-half inch long. These oblong cones often stand upright and possess only a few thin, overlapping scales that mature within a single season.
Mature Arborvitae bark is characteristically fibrous and reddish-brown, tending to peel off in narrow, longitudinal strips. The overall growth habit of most cultivated varieties is dense, columnar, or pyramidal, making them popular for structured landscape design.
Key Identifying Features of True Cedars
True Cedars (Cedrus species) possess foliage fundamentally different from Arborvitae. Their leaves are genuine needles, which are short, stiff, and typically measure one to two inches long. These needles grow in dense, small clusters or rosettes on short, woody projections known as spurs.
True Cedars produce large, barrel-shaped female cones that stand upright on the branches. These cones can be three to four inches long. Unlike the cones of most other conifers, True Cedar cones disintegrate while still attached to the branch, scattering their seeds.
The bark of the Cedrus genus tends to be rough, scaly, and deeply furrowed on mature specimens, often appearing silvery-grey or dark brown. Species like the Cedar of Lebanon exhibit massive, widely-spaced branches that create a broad, layered silhouette as they age.
Practical Implications for Landscaping and Care
The distinction between Arborvitae and True Cedars is important for homeowners because their care requirements and eventual sizes vary drastically.
Size and Usage
Arborvitae are widely utilized for privacy screens and hedges due to their dense foliage and natural tendency toward columnar or pyramidal shapes. Varieties like ‘Green Giant’ and ‘Emerald Green’ tolerate heavy shearing and can be maintained at a manageable height and width.
True Cedars, which include the Atlas Cedar and the Cedar of Lebanon, are generally unsuitable for small residential properties or hedging purposes. These are grand, specimen trees that often mature to heights well over 100 feet with massive, spreading canopies that can span 50 to 80 feet wide. Their ultimate size means they require significant open space to develop their characteristic form.
Environmental Needs and Pruning
Arborvitae prefer moist, well-drained soil and often struggle with dry, exposed, or windy sites, which can lead to browning or “winter burn.” They are also highly susceptible to deer browsing.
True Cedars, originating from mountainous regions, typically exhibit greater drought tolerance once established but are difficult to successfully transplant once mature due to their deep taproot systems.
Pruning methods also differ significantly. Arborvitae responds well to the repeated, formal shearing needed for hedges. Conversely, True Cedars do not tolerate aggressive pruning and are best left to grow naturally, perhaps only requiring the removal of lower limbs for clearance. A homeowner’s choice should be guided by their garden size and the required maintenance, as the needs of a small Thuja are vastly different from those of a large Cedrus specimen.