The Douglas-fir is a dominant tree, both in abundance and stature, around Nanaimo. Douglas-firs tolerate a range of conditions, and can grow even in very dry sites. This trait allows them to survive our long dry Nanaimo summers well. Full grown Douglas-firs can reach about 70 m (230 feet) tall, and in favourable sites with sufficient moisture they can grow even taller.
The Douglas-fir is named in honour of David Douglas, a plant hunter who came to the Pacific Northwest from Scotland in the 1800s. Douglas brought back many plants from here to Europe, where they are now in cultivation.
Of course, this tree was well known and used by First Nations people all across our area for thousands of years. Some of the uses were for heat (fires) and technology (e.g. spear handles), but also medicinal (e.g. using the pitch for salves).
Douglas-fir (Pseudotsuga menziesii) Photo credit: Douglas Fraser
Oftentimes, when walking through the wood, we can’t easily see the foliage (leaves/needles) of the tall trees around us. In those instances, we need to be able to identify a tree by its bark. The bark of mature Douglas-firs is deeply grooved and a bit corky. The thick bark protects the tree from ground fires.
Note the deeply grooved bark of the Douglas-fir. Photo credit: Douglas FraserNotice the scorched outer bark of this Douglas-fir trunk. Large specimens like this one can survive forest fires well, but young trees would be killed if the fire destroyed the living tissue layer under the bark. Also, note the presence of English ivy (Hedera helix) climbing up the trunk. English ivy is a highly invasive plant in our ecosystem. It smothers other plants in the understory, and compromises the health of trees by shading out the trees’ own leaves and needles. Photo credit: Douglas Fraser
If we encounter a small enough specimen of Douglas-fir, then we can inspect its branches and needles. Note that the needles are arranged in a spiral pattern (alternate pattern) around the twig. If you grabbed the branch with your hand and gave it a gentle squeeze, you’d notice that the needles are quite stiff and a bit pointy (this is in contrast to Western hemlock – Tsuga heterophylla, which has very soft branches).
End of Douglas-fir branch showing the needles. The needles are arranged alternately (spirally around) the stem. Photo credit: Douglas Fraser If you look closely, you can see how the individual needles are attached to the stem in a spiral (‘alternate’) pattern. Photo credit: Douglas FraserA close-up of the needles show two white stripes on the underside (abaxial side) of the needle, and a single vein on the top (adaxial) side. The white color is due to the presence of epicuticular waxes that covers rows of stomatal pores. The waxes form complex structures above the stomata to help slow down diffusion of water from the needles to the atmosphere – contributing the the drought tolerance of Douglas-firs. Photo credit: Douglas Fraser
What about sexual reproduction? Douglas-firs are ‘gymnosperms’ (gymno = naked, sperm = seed), and as such they make their spores (which develop into the gamete producing gametophytes) in specialized structures called ‘cones’ (synonym: ‘strobili’). The ‘male’ cones, where pollen is eventually produced are small, with papery scales. The ‘female’ cones, where eggs and later seeds are eventually produced, are larger and woody.
This is a close-up of a male cone / pollen cone of Douglas-fir. Notice how small this cone is, it’s usually shorter than the needles. You may have encountered these cones in spring when they release enormous amounts of pollen. The cones deteriorate and fall off the tree once pollen has been released. By mid-June, you see droves of spent male Douglas-fir cones on the streets and sidewalks around Nanaimo. Photo credit: Douglas FraserThe spent male pollen cones of Douglas-fir on a Nanaimo sidewalk in June. This is a young female Doug-fir cone. The egg-bearing structures (the ‘ovules’) are hidden on the inner surfaces of the cone scales. Note the 3-forked bracts that stick out between the cone scales. If you use your imagination, you can see that these are the tails and hind-legs of little mice that are hiding inside the cone – this is a unique characteristic for Douglas-firs and will help you distinguish these cones from all other conifer cones. Photo credit: Douglas FraserHere are two mature female Douglas-fir cones. Note how the cone scales have opened up. The seeds that were hidden between the scales have probably been released and blown away by now. The 3-forked bracts are still there – a good clue that these are Douglas-fir cones. If you find cones such as these, you can peek between the scales and perhaps find some residual seeds, or at least note the imprint of where the seed used to be resting on the scale. Photo credit: Douglas FraserThis is a Douglas-fir seed. Note the thicker portion to the right, this is where the embryo and its nutritive tissue resides. The left-hand, thin, papery, portion of the seed is a wing that allows the seed to drift for awhile on the wind – hopefully dispersing a bit away from the mother tree and landing in a favourable spot. Photo credit: Dave Ingram
You can find Douglas-fir trees almost all over Nanaimo. Please step out and find some for yourself!
For a comparison between leaf/needle and female cone characteristics of the four conifers listed on this site, please see this conifer comparison page.
