Plant of the Month: Mountain Hemlock
I have a lot of respect for mountain hemlocks (Tsuga mertensiana).
They’re tough, living at high elevation in the mountains where they get hammered with wave after wave of winter storms. Young trees may get buried completely by snow, hidden for months by a deep white blanket. Old trees take on a grizzled appearance, encrusted by rime ice after nearly every storm.
If you ski at any of Washington’s west-side ski areas you’ve seen mountain hemlocks, together with subalpine firs. You can easily recognize younger hemlocks by the characteristic nodding top, bent over whether under snow or not. Old trees may have their tops broken off. When you stop to catch your breath at the side of a ski run, look for the furrowed brown bark of the hemlock, in contrast to the smoother silvery bark of the firs. Upon even closer examination, notice that the hemlock needles are short, just a half-inch or so long, and arranged all around the twigs, with a somewhat ragged appearance.
Mountain hemlock is native to all of the Pacific Northwest, ranging south to California and Nevada and east to Montana. It’s almost always at higher elevations, in contrast to the lowland western hemlock (Tsuga heterophylla). In our part of the North Cascades, up around Mt Baker, the dividing line between the two species is around 2,500-3,000 feet. Distinguish the two species by the arrangement of the needles on the twig. Western hemlock needles are arranged in flat sprays on opposite sides of the twigs instead of circling them.
Even though mountain hemlock isn’t native to low elevations, it is perfectly happy to grow near sea level when planted in a garden. It’s a slower-growing tree than western hemlock, so it makes a good choice for a smaller garden. Needles are deep blue-green and when grown in the open the tree assumes a narrow conical form. We’re planning to plant one or more of them in the landscape around our new studio. A few named cultivars, including dwarf varieties, are also available in the nursery trade. Locally, Cloud Mountain Farm carries the species and two varieties.
I wrote also about mountain hemlock back in December, 2010. It’s one of my favorite trees, whether I’m out skiing or snowshoeing in the winter or hiking a mountain trail in the summer.
