Northern White Cedar (Thuja Occidentalis) differs from Western Red Cedar (Thuja Plicata) in leaf color (dull, yellowish green on both surfaces), seed cones scale formation, tree size, and geographic regions of growth. The Northern White Cedar's primary geographic growth area is lower Canada, and the perimeters of colder, swampy regions of the Great Lakes. Western red cedar has a reddish caste and Northern White Cedar is yellowy-beige in color. Western Red and White Cedar are aromatic. The face grain is very similar between the two so looking at the end grains is the best way to identify the species of wood. Although in general the decay resistance of the two trees are similar, there is a marked difference in the lumber itself. The core of the tree is the heartwood annd the best decay resistant product you can buy is the heartwood section of the tree. The white cedar will normally have the heartwood of the tree in nearly 100% of your lumber pieces. Red Cedar may have the heartwood of the tree in about 10% of the lumber pieces. Why? Because Western Red Cedar trees are significantly larger in diameter than Northern White Cedar. Perhaps the most important difference is COST. If you are building in areas from the Rockies to the eastern seaboard of the United States, you will save significantly on shipping costs by purchasing locally grown, harvested and milled Northern White Cedar.