Plant Spotlight: Tsuga Heterophylla

What it Is

 Western hemlock's delicate evergreen foliage provides interest throughout the winter.

Western hemlock's delicate evergreen foliage provides interest throughout the winter.

Western hemlock, Tsuga heterophylla, is the state tree of Washington, where it mostly grows in the Cascades and the Olympic Peninsula. It prefers shady, moist conditions and is not found native in Spokane County, but it does grow throughout the Idaho Panhandle. Trees in the wild can grow to 100’ high and 30’ wide, but are smaller in cultivation.

Why to Grow It

Western hemlock is an attractive conifer tree for shady spaces. Its small needles and cones offer delicate evergreen interest, and it is a good tree for attracting birds. There are only a few cultivars cultivars available currently, but Tsuga heterophylla’s superior resistance to the hemlock woolly adelgid makes it a more reliable choice than the widely grown Tsuga canadensis. The insect is steadily devastating hemlock populations throughout the Eastern US, but western hemlocks do not show the same mortality when infested.  

Where to Put It

At least partial shade is necessary for the western hemlock in the Spokane/Coeur D’Alene region, where our hot, dry summers can stress the tree. Northern and eastern exposures are preferred, and Tsuga heterophylla does well in moist soil, as long as it is well-draining. The lacy, evergreen foliage is a great addition to a woodland or shade garden. Its soft needles won’t poke or jab like many other conifers, making it a suitable choice next to patios or pathways, where people might brush against it.