As summer drains away and autumn brings cooler temperatures and snow to the mountains, Central Oregonians might find comfort in our wealth of evergreen trees. But how much do we know about these regional icons?
To better acquaint readers with some of Central Oregon’s diverse evergreens, The Bulletin spoke with David Shaw, a forest health specialist and an associate professor in Oregon State University’s Department of Forestry. Shaw rattled off factoids of the five most common evergreens to help make blustery walks and runs through the area’s gazillion trees a bit more familiar. Identification details are provided by “Trees to Know in Oregon,” by Edward C. Jensen.
If it were up to Shaw, the ponderosa pine would be Oregon’s state tree — not the Douglas fir — both of which were named by Scottish botanist David Douglas. “The ponderosa pine, our classic pine, is a really beautiful tree that characterizes many of the state’s landscapes,” Shaw said. In Central Oregon, ponderosa is found in the lower regions before the land gives way to sagebrush and western juniper. Although the pine does OK in some level of shade, it prefers full sun. Ponderosa grows in tight groves, where as an adolescent it’s known as black pine for its dark trunk. At maturity, the trunk acquires the yellow-orange palates it is known by. When Shaw presses his nose close to the deep furrows in the ponderosa pine bark, he picks up a vanilla scent — others whiff butterscotch. Ponderosa pine extends from lower elevations where it lives in open, park-like stands — and where the fire-return interval used to range from 5 to 20 years — well into the mixed conifer forests. It’s the second-most common tree in Oregon, second to the Douglas fir.
Key identifiers: Ponderosa pine needles “are 5 to 10 inches long and usually grow in bundles of three. Groups of needles are tufted at the ends of branches. Its egg-shape cones are 3 to 6 inches long.”
Another important pine in Central Oregon is the aptly-named lodgepole, whose slender trunk is a common sight. Native Americans and white homesteaders alike constructed lodges from the tree. Near La Pine, this variety grows on the pumice plain. Lodgepole pine has adapted to the micro climate, which features cold air that blasts in from the Cascade Range. Few trees grow there due to the fluctuating air temperature from morning to night and the pumice soil, Shaw said. Lodgepole, conversely, thrives despite these heating and frosting mechanisms. Elsewhere in Central Oregon, lodgepole is found in more conventional mixed conifer settings higher in the mountains. As a local quirk, our lodgepoles’ cones, which are sealed with resin, do not participate in serotiny — a heat-activated release of seeds. Most often, wildfires trigger this process. Experts don’t know why Bend’s lodgepole pines have little to no serotiny, which was first observed by early botanists in the area.
Key identifiers: Lodgepole is the only native Oregon pine whose needles grow in bundles of two. Its “prickly, egg-shaped” cones are rarely longer than 2 inches.
Douglas fir and grand fir
We’re lumping these two together because they’re often neighbors in the same mixed conifer forests in mid to high elevations in Central Oregon. The more famous of the two, the Douglas fir (which arborists and botanists write as Douglas-fir to denote the tree as a false fir — not a member of the fir tree family), is Oregon’s state tree, mainly for its long-running reputation as a hearty lumber, Shaw said. On the east side of the Cascades, the Douglas fir has thick bark that is resistant to ground fires and grows at many elevations and habitats. The wood’s hardiness, which fends off root diseases, makes it popular for structural two-by-fours. By contrast, the grand fir has a soft wood and wounds easily. In the lumberyard, it is found hybridized with the western hemlock, whose product is called “hem-fir.” Both the Douglas fir and the grand fir are susceptible to the western spruce budworm, which is an infamous cause of major forest defoliation. Nonetheless, in managed mixed conifer zones, the Douglas fir and the grand fir have been doing almost too well. Forest restoration efforts have reduced the amount of Douglas fir and grand fir in any given stand to increase the pine and larch populations. One of the most telling characteristics of the grand fir is its seeping resin, which often surfaces in little bubbles on the bark and is very sticky. The old-fashion way to remove resin from skin was by washing it with gasoline, “but we don’t recommend that any more,” Shaw said with a laugh. Hand cleaners such as Goop are a safer alternative.
Key identifiers: Douglas fir’s cones features “three-pointed bracts sticking out between the cones scales like little tongues. Even young saplings have cones.” Grand fir has needles “that point to the side and grow in two distinct rows (either flat or V-shape).”
Yes. This is a list of evergreens, but the western larch’s weird needly deciduousness is too cool to ignore. While its branches are covered in green needles, the western larch is the only native conifer — or any evergreen tree or shrub bearing needles or scale-like leaves — that loses its needles in the winter. During autumn, its bundled needles turn a bright yellow, adding shocks of warmth to our regional forests’ color palate.
“Oftentimes, people who aren’t familiar with the western larch think the tree might be dying or losing its needles for some reason. But it happens every year,” Shaw said. “The western larch is a classic deciduous.” In spring, new foliage sprouts and its beautiful green tinge distinguishes it from other trees.
The western larch is more resistant to root diseases and pests than Douglas fir and grand fir, two of its typical neighbors.
The thickly-barked, fire-adapted variety favors high light and is often one of the first trees to repopulate an area after a fire. Well known in the insect world, the western larch suffered greatly in the 1950s when a nonnative, invasive moth called the western larch casebearer ate all of its needles throughout its range.
In the ’60s and ’70s, the U.S. Forest Service introduced parasitic wasps, which paralyze the moths during their caterpillar stage and lay eggs on their bodies, which the wasps’ larvae soon devour. Yikes.
“It’s a success story for biological control,” Shaw said, adding that the wasps are still playing a role in maintaining the health of the western larch.
Western larch occurs in dry mixed conifer forests, higher above the zone where ponderosa pines grow.
Many western larch are found along the Santiam Pass near Suttle Lake. Sisters is the southern boundary of the tree’s range, which stretches along the eastern side of the northern Cascade Range and in the Blue Mountains in northeast Oregon and eastern Washington.
Key identifiers: Aside from shedding its yellowed needles in autumn, the western larch can be identified by “the stout, woody pegs that supports the needles and its ‘whiskery’ cones.”
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