The common question of whether Douglas Fir and Cedar are the same wood has a clear answer: No, they are not. Both are highly valued commercial timbers native to North America, especially the Pacific Northwest, and both are conifers. This misconception arises from confusing common names and similar applications in construction. Understanding the distinct biological lineage and physical properties of each species is key to differentiating these two popular materials.
The Botanical Distinction
The formal scientific classification, known as the Linnaean taxonomic system, immediately separates Douglas Fir from true Cedars. Douglas Fir belongs to the genus Pseudotsuga and is a member of the Pine family (Pinaceae). The genus name Pseudotsuga literally translates to “false hemlock,” which highlights the historical difficulty in classifying the tree.
Douglas Fir is not a true Fir, which belongs to the genus Abies, nor is it a true Cedar, which belongs to the genus Cedrus. True Cedars are native to the Mediterranean and Western Himalayas. The wood commonly sold as “Cedar” in North America, such as Western Red Cedar (Thuja plicata), is actually a member of the Cypress family (Cupressaceae).
This means Douglas Fir and popular Western Red Cedar belong to two entirely different plant families. Scientific nomenclature provides a standard, unambiguous way to distinguish species.
Physical Differences and Properties
The practical differences between the woods are immediately apparent in their scent, color, and density. Western Red Cedar is renowned for its strong, pleasant aroma due to natural oils, and its color ranges from light amber to a rich reddish-brown. Douglas Fir, in contrast, has a milder, more resinous odor when worked and typically presents a pale yellow-to-light brown color, sometimes with reddish streaks.
Douglas Fir is significantly denser and harder than Cedar, making it the preferred choice for structural applications. On the Janka hardness scale, Douglas Fir scores around 660 pound-force (lbf), while Western Red Cedar is much softer, scoring only about 350 lbf. This superior strength-to-weight ratio makes Douglas Fir ideal for framing, beams, and heavy construction components.
The natural resistance to decay also distinguishes the two woods. Cedar contains natural fungicidal and insecticidal compounds called thujaplicins, granting it superior, inherent resistance to rot and insects. Douglas Fir heartwood is rated as moderately durable, but it generally requires chemical pressure treatment or a heavy sealant for long-term exterior durability. Cedar’s natural oils allow it to resist moisture and decay without the need for chemical treatment, making it a lower-maintenance choice for non-structural outdoor items like siding and shingles.
Why the Names Are Confused
The confusion between Douglas Fir and Cedar stems largely from historical naming conventions and commercial simplification. Early explorers and foresters often assigned common names based on a tree’s physical resemblance to a familiar European species, leading to inaccuracies. For instance, Douglas Fir was named after botanist David Douglas, yet its scientific name honors Archibald Menzies, and it is sometimes commercially called “Oregon Pine,” even though it is not a true pine.
Many North American species are colloquially called “cedar” despite not belonging to the true Cedrus genus. Eastern Red Cedar is actually a Juniper (Juniperus virginiana), and Western Red Cedar is a Thuja. This pattern of applying the name “cedar” to any aromatic, rot-resistant wood has blurred the botanical lines for the average consumer.
The wood products industry also contributes to the confusion by grouping woods based on similar practical uses or general appearance rather than scientific accuracy. While Douglas Fir is prized for its strength and Cedar for its decay resistance, both are popular, widely available, and used in general construction. Despite the similar applications, their distinct botanical origins and differing properties confirm that Douglas Fir is a separate and unique species from any true or false Cedar.