Alnus rhombifolia

Alnus rhombifolia is a medium-sized deciduous tree growing to 49-82 ft rarely to 115 ft tall, with pale gray bark, smooth on young trees, becoming scaly on old trees.

The flowers are produced in catkins. The male catkins are pendulous, yellowish, and produced in clusters of two to seven; pollination is in early spring, before the leaves emerge. The female catkins are ovoid, when mature in autumn and resemble a small conifer cone. The small winged seeds disperse through the winter, leaving the old woody, blackish ‘cones’ on the tree for up to a year after.

The White Alder is closely related to the Red Alder (Alnus rubra), differing in the leaf margins being flat, not curled under. Like other alders, it is able to fix nitrogen atmospheric nitrogen, and tolerates infertile soils.

If used domestically they should be planted well away from drainpipes, sewage pipes, and water lines, as the roots may well invade and clog the lines. These fast-growing trees often grow 3 ft. per year until 20 years of age. They are a relatively short lived species compared to other PNW native tree species.

Calocedrus decurrens

Incense cedar is a conifer native from central-western Oregon through most of California. It has a distinct symmetrical shape and can get up to 90 feet tall in its native habitat.

The bark is orange-brown weathering grayish, smooth at first, weathering to grayish, fissured bark that sheds in long strips on the lower trunk on old trees. The fragrant, bright-green foliage is produced in flattened sprays with scale-like leaves. The seed cones look like the open beak of a duck. They turn orange to yellow-brown when mature about 8 months after pollination.

Many birds depend on insects that live on incense cedar, including woodpeckers, brown creepers, red-breasted nuthatches, and golden-crowned kinglets. Birds use the dense foliage for nesting in the summer and shelter in the winter. This tree is also the preferred host of a wood wasp, Syntexis libocedrii, a living fossil species which lays its eggs in the smoldering wood immediately after a forest fire.

Cultivation and Uses

The wood is the primary material for wooden pencils, because it is soft and tends to sharpen easily without forming splinters. It is also a popular ornamental tree, valued for its drought tolerance. In cool summer climates (such as in Washington, British Columbia, etc.), incense cedar tends to grow narrower than in the wild, making it a good choice for large hedges and screens.

Fraxinus latifolia

Note: Due to the recent arrival of emerald ash borer in Oregon, ash trees in our region are at high risk of mortality over the next several decades. See OSU Extension Service’s emerald ash borer resources page for more information about how you can slow the spread and protect your ash trees.

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Oregon ash is native to western North America on the west side of the Cascade Range from southwestern British Columbia south through western Washington and western Oregon to central California.

It can grow to 80 ft in height, with a trunk diameter of 3ft. The leaves are pinnate, 3.5-10″ long, with 5-9 ovate leaflets. The fruit is a samara, 3-5 cm long including the wing. The leaves turn a striking yellow in the fall.

Oregon ash prefers damp, loose soils, and grows from sea level to 900 meters. It is a dominant tree in local forested wetlands, paired with an understory of spiraea and slough sedge.

Oregon ash is an ideal deciduous tree to plant along streams, seeps, and wet areas. It forms an attractive shape, tolerates saturated soils, and shades waterways.

Pinus ponderosa

Willamette Valley Ponderosa Pine (Pinus ponderosa var. benthamiana) is a beautiful tree with long needles and attractive bark. Like all ponderosas, the bark of this tree has a vanilla-like scent when warmed by the sun–and they love sunny spots! However, the Willamette Valley Ponderosa is the only variety of ponderosa that can also withstand the heavy wet winter soils of our region.

This long-lived tree is very valuable for wildlife. Its needles are the only known food for gelechiid moth (Chionodes retiniella) caterpillars. Many species of birds and small mammals eat the nutritious seeds and use the needles for nesting material; others use cavities and branches for nesting and shelter.

Willammette Valley Ponderosa Pine is one of four different varieties of Ponderosa Pine, each adapted to different climatic conditions and with differing botanical characteristics. When planting in Multnomah County, it is very important to use this variety, as it is the only one that will thrive in our region.

Populus trichocarpa

Balsam poplar (Populus balsamifera) is the northernmost American hardwood, and grows across the continent. Though it appears in upland areas, it thrives in floodplains. It is our tallest native broad-leaved tree, and has dark grey bark. In the spring and early summer the sticky resin on leaf buds releases a strong, balsamic fragrance. It is hardy, fast-growing, and relatively short-lived, though some trees have been known to live for 200 years. Other names are balm-of-gilead, bam, tacamahac, cottonwood, or heartleaf balsam poplar.

Wildlife

The leaves of the balsam poplar serve as food for various caterpillars in the order Lepidoptera. It is an important browse for deer and elk and provides nesting habitat for large birds. The anti-infectant property of the resin is used by bees, who seal intruders in it to prevent decay and protect the hive.

Uses

A great riparian restoration species. The light, soft wood is used for paper pulp and construction lumber.

Pseudotsuga menziesii

Douglas fir is one of the most common evergreen trees in the our region. It grows fast and can tolerate many soil types. This is a good tree to plant in groups as a windbreak, or at the edge of wooded areas, as it needs plenty of space.

The bark is thin, smooth, and gray on young trees, and thick and corky on older trees. The needle-like leaves are spirally arranged and 2-3.5 cm long, and a bud at the tip of most branches distinguishes it from other evergreens. Douglas fir foliage has a noticeable sweet fruity-resinous scent, particularly if crushed. The 2-4 inch long cones are green in spring, maturing to orange-brown in the autumn 6-7 months later. The male cones disperse yellow pollen in spring.

Many kinds of wildlife depend on Douglas fir for winter forage. Mice, voles, shrews, chipmunks, pine siskins, song sparrows, golden-crowned sparrows, white-crowned sparrows, red crossbills, dark-eyed juncos, and purple finches all eat the abundant seeds. Black-tailed deer and elk will eat the seeds late in winter when other forage is scarce. The Douglas squirrel harvests and caches great quantities of Douglas fir cones for later use, and the squirrels will also eat mature pollen cones, the inner bark, terminal shoots, and tender young needles.

Fun facts: Douglas fir (Pseudotsuga menziesii) is neither a true fir, nor is it a hemlock (hence the Latin name, *Pseudo*tsuga). It is its own genus altogether. It is also the second-tallest evergreen in the world after the Coast Redwood. Trees 200-250 feet or more in height and 5-6 feet in diameter are common in old growth stands, and heights of 300-400 feet were reported by early lumbermen. It commonly lives more than 500 years and occasionally more than 1,000 years.

Quercus garryana

The iconic Quercus garryana, also known as Garry oak and Oregon white oak, is a drought tolerant tree that can also tolerate prolonged seasonal flooding. It can often grow on sites that are too dry for other tree species. These slow-growing trees are smaller at maturity than many Pacific Northwest trees, growing eventually to a maximum size of 65-80 ft tall and wide. They have deep tap roots and widely spreading roots, making them resistant to wind-throw. Mature trees growing in open areas develop broad oval crowns, making them excellent shade trees.

The leaves are deciduous, 3-6″ long and 2-5″ broad, with 7-9 deep lobes on each side. The flowers are catkins, and the fruits are small acorns about 1″ long with shallow, scaly cups.

Over 200 species of wildlife benefit from Oregon white oaks, including pollinators such as Fender’s blue, Taylor’s checkerspot, Mardon skipper, Islad marble, and the Oregon silverspot. The Oregon white oak is also the only known food for the caterpillars of Propertius duskywing butterflies and a leaf-mining moth. Deer, bear, raccoons, squirrels, and many small mammals eat the acorns, as do wild turkeys, band-tailed pigeons, woodpeckers, jays, and others.

Oregon white oaks also have significant cultural value for many Native tribes. For all these reasons, Oregon white oaks and their associated prairie habitats are the focus of many regional conservation efforts.

Thuja plicata

Western redcedar (Thuja plicata) is a large evergreen conifer treasured not only for its beauty, but also its wildlife value and cultural significance going back to time immemorial.

Mature Western redcedars can get 115 – 230 feet tall. The flat, elegant sprays of foliage makes the tree look like it is draped with lace, especially when dusted with frost or snow. The cones are slender with overlapping scales. This tree is actually part of the cypress family, and not a true cedar (just like Douglas-fir is not a true fir).

Western redcedars make excellent wildlife habitat, providing food and shelter for many species. Rosners hairstreak butterflies are only found in association with this tree, as they depend on it for reproduction and food for their young. Large and small mammals feed on the leaves and inner bark for most of the year; squirrels and other rodents use its shredded bark for winter nests; and many birds and small mammals find shelter and nest sites in red cedar cavities.

Western redcedar is a iconic tree of the Pacific Northwest. If you have a shady, moist spot large enough for it to thrive, this is a beautiful and valuable addition to any forested landscape.