Oh Christmas Tree!
When you think “Christmas tree” you’re probably conjuring up a conifer. They’re those trees with (generally) evergreen needle-like leaves that bear their seeds in woody cones. Those cones are where the name conifer comes from.
Here in the Pacific Northwest conifers are the backdrop for most of our landscape, whether in the wild or the garden. In fact, if you throw a rock anywhere on the west side of the Cascades and hit a tree you’ve probably found a Douglas-fir, Pseudotsuga menziesii. It’s our most common conifer and is native from the Rocky Mountains to the Pacific Ocean. There are three varieties, but we’ll not bother with that detail today.
Douglas-fir is the most commonly planted timber tree in the northwest because it grows relatively quickly, tall, straight, and produces quality lumber. It’s also the most commonly grown Christmas tree. That’s because it tolerates a wider range of growing conditions than most other conifers. If you lived on the east coast you’d be more likely to encounter Scotch Pines, a tree more adapted to eastern growing conditions, on the Christmas tree lot.
Douglas-fir has been grown commercially for Christmas trees since the 1920s. Starting in the 1950s growers started shearing their trees for denser branches. In the wild, Douglas-fir has a more open structure.
I never recommend that anyone plant a Douglas-fir in their garden unless they have a very large space. These trees can live over 500 years, grow to six feet in diameter and 250 feet high. Regardless, there are cultivars of Pseudotsuga menziesii available in the nursery trade. Iseli Nursery offers five. Of course, you can always decide to plant Doug firs for a short-term specimen and plan to cut them down when they get too big for your space.
Douglas-fir is an important tree for wildlife. I often find deep middens of cone scales under trees in our forests. Squirrels nip the cones off the branches then collect them from the ground. They’ll often sit in one place and extract the seeds. One of the ways seeds are dispersed is from the cones the squirrels can’t find or forget to pick up. In mature specimens nearly the entire surface of the tree is draped in epiphytes — dozens of species of mosses and lichens. Birds like the northern spotted owl require mature old-growth Douglas-fir forests, as do red tree voles. That small mammal nests almost exclusively in Douglas-fir and it’s diet is mostly Douglas-fir needles. Cavities in old snags are important nesting sites for several bird species. Deer delight in munching new growth on seedlings and saplings.
Douglas-fir is relatively resistant to fire. Mature trees have thick, corky bark and the crown is often high above the ground. I’ve visited sites that have burned numerous times. There are burn scars on the bases of the Douglas-firs, often a hundred years old or more.
Despite having “fir” in it’s name, Douglas-fir is not a true fir. The Latin name, Pseudotsuga, means false hemlock. True firs have cones that sit upright on top of upper branches. Douglas-fir cones hang below the branches. They have distinctive forked cone scales that resemble mouse ears. Cones mature in a single season, usually ripening by August. Learn more about Douglas-fir at the US Forest Service Fire Ecology site.
I have more photos of Douglas-fir on my Pacific Northwest Wildflowers website.