Mountain Hemlock

Mountain hemlock is a native conifer of high elevations from southern Alaska to central California. It reaches 30-100 ft with an erect form and slow growth. It produces yellow flowers and brown cones with fine, gray-green foliage.

Mountain hemlock is hardy in zones 5a-8b and prefers partial shade with well-drained soil (pH 4.5-7.3). It requires high moisture and long cold winters with heavy snowpack. Growth is slow and takes decades to reach mature size. It is notably intolerant of low-elevation, warm summer conditions.

Mountain hemlock is a high-elevation species that does not belong in the Puget Sound lowlands. It requires long cold winters with heavy snowpack, cool summers, and 42-140 inches of annual precipitation concentrated in the mountains. Planted at sea level in Kent, it will suffer from summer heat, inadequate cold dormancy, and disease pressure from root pathogens that are absent at its native elevation. If you want a hemlock for a lowland landscape, plant western hemlock instead. Mountain hemlock belongs above 3,000 feet.

— Chris Welch, ISA Certified Arborist