Scientific Name
Thuja plicata
Western red cedar, sometimes called giant arborvitae, is a majestic conifer and an iconic part of the northwest U.S. forests. Despite its common name, it is not a true cedar (genus Cedrus) but belongs to the Thuja genus, which also includes smaller arborvitae often used in urban landscapes. Its native range stretches along the Pacific coast from northern California to the border of British Columbia, and inland through the northern Rockies of Idaho, Montana and interior British Columbia. The wood is highly valued for its decay resistance. In the wild, these trees can exceed 200 feet tall, though cultivated specimens typically reach around 70 feet.
The evergreen foliage forms flat, fan-shaped sprays with tiny scale-like leaves. Both male and female cones are small and often overlooked. The reddish stringy bark adds character even on mature trees. Western red cedar thrives in fertile, moist, acidic soils and can withstand temperatures as low as minus 20°F.
Growing it in Colorado presents challenges due to our sunny, dry winters. Foliage can “bronze,” turning reddish-brown or even desiccating because the bright winter sun and frozen ground prevent the tree from maintaining adequate moisture. At Regis, a northern Idaho seed source has fared best. By planting it in the winter shade of two large ponderosa pines, the cedar avoids excessive bronze while still receiving enough summer sun. One intriguing question remains for the future: what will happen when this tree grows tall enough to rise above the winter shadows cast by the pines?