Lushootseed names: sək̓ʷəbac (ss-ack-wo-bots)

Location: Growing on the north side of a diagonal walking path running northwest from East Stevens Way Northeast just before the road begins to turn. The tree is located due south of the archery range in a small grove.

Summary: The Red Alder belongs to a category of trees which live fast and die young (relatively speaking). While some of our native silva can persist many hundreds or even thousands of years in the right circumstances, Alnus rubra lives its life on a more human timescale. This species often begins its life immediately after a disturbance, such as a flood, fire, or (more recently) logging. Too small to compete with coniferous giants common in this region, Alder will take advantage of the openings created by disturbance forces that cause large mature trees to fall and sunlight to reach the forest floor. Once these trees have germinated, it is a race! Alders only grow to about 100’ tall, and need to grow fast to get a head start above those other trees which can. This fast growth results in relatively weak wood, and by the time these trees are reaching octogenarian status, they have begun to rot and come apart bit by bit. 

Growing in recently disturbed sites can be challenging; there is often a lack of readily available nutrients in soils depleted of organic matter by erosion, fire, or human modifications. However, the Red Alder has an incredible advantage for growing on sites unfit for other tree species. All plants need nitrogen in order to survive, but even though this is the most common element in earth’s atmosphere, it must first be converted out of its gaseous form before it becomes available to plants or animals. Although Red Alder cannot make this conversion itself, it has friends in low down places who are willing to turn nitrogen gas into a usable ammonia form (for a price). Within the roots of Red Alder lives a type of bacteria called Frankia, which takes up residence in specialized nodules created by the tree to host this soil-dwelling neighbor. Through a process called nitrogen fixation, Frankia provides its host with ample amounts of this essential element, and in exchange receives energy and carbon from Alders. This symbiosis (or collaboration) between the two species allows Alnus rubra to grow even on soils denuded of nutrients. The wealth of this tree may be seen in fall, where, rather than withdrawing nitrogen into the trunk, the species will simply let it fall with the leaves. As a result, these leaves remain fairly vibrantly green even as they tumble to the ground. These nitrogen-rich leaves act as a marvelous fertilizer, and many a garden and farm could benefit from a nearby Alder to provide mulch. Red Alder also produces constituents which aid in clearing the lymph nodes, and is traditionally used by the Coast Salish peoples for this medicinal purpose. The species is additionally the preferred firewood for smoking salmon, and for the creation of red-orange dye.

Identifying Features light: The red alder is an extremely distinctive tree of the Pacific Northwest, a deciduous successional species which is often the first to colonize a disturbed site. Its bright green foliage is made up of ovate or elliptical leaves which have double serrated margins (meaning a larger pattern of serrations is overlaid by even smaller teeth). The pinnate venation of these leaves is bold, with each secondary vein running to the tip of one of the larger serrations. The bark of these species is generally smooth and a splotchy white or gray in color, often with wart-like protrusions and sucker growth emerging from the trunk. One extremely distinctive feature of these trees is their cone-like fruiting bodies, which are slightly larger than marbles and at first glance appear to come from a coniferous species. They are in fact a form of catkin and occur in clusters which fall to the ground and surrounding bushes often still connected to their bundle.

Identifying Features In Depth:

1. Form: A first successional species, this tree often appears in disturbed sites forming dense groves. More successful trees form a broad domed crown to a height of 120’ (25m), but in an environment where light is more difficult to obtain they may take a more narrow form. They often have a thick main trunk rising to several significant branches higher up. Often the lower part of the trunk has sucker growth. The trunk may achieve a width of 1-3’ (0.3-0.9 m).

2. Leaves: Leaves are highly distinctive, bright yellow-green, often with slightly hairy undersides, 3’ (15 cm) in length and ovate or oblong in shape. They are double toothed, with broad wavy points around the margin covered with a finer layer of smaller teeth. The veins are pinnate, running distinctively to the major serrations on the margin. They have a grooved petiole.

3. Bark: The bark of these trees is beautiful, smooth and thin and of an ashy gray color speckled across it. The outer bark is in no way red, but just below the surface the reason for the tree’s name becomes apparent with its vibrant underbark, a brilliant red which can be used to make dye. Often the tree will have wart-like growths on the bark and evidence of past branches now fallen.

4. Reproductive Bodies: The reproductive bodies of this deciduous species are distinctly conelike in appearance, although closer inspection shows them to be different from true cones. These catkins stand erect on orangish stalks, fading from green to dark brown with age and grouped in clusters with other fruiting bodies. Often the male fruiting bodies may be found in these groups once they have fallen from the tree. They are ovular in shape and a little bigger than a marble.

Historical Background:

Also called the Oregon Alder, these trees have a distinctive role to play in Pacific Northwest ecosystems, a role which has gained them the nickname “hero tree”. All plants need nitrogen to survive, but although it is the most abundant element in the earth's atmosphere, most plants cannot access this necessary element in its gaseous form and must instead draw it from the soil in which they grow. In a region of such high rainfall and with so much vegetation, supplies of soil nitrogen are extremely limited. Fortunately, the Red Alder forms what is called a mutualistic symbiosis with a group of mycorrhizal fungi known as Frankia. Basically, this means that the Red Alder enters into a relationship with a type of fungus that is beneficial to both the tree and the fungus. Frankia have a special ability which the tree lacks, they can draw atmospheric nitrogen from the air and convert it to a form which can be used by plants, but the process takes a lot of energy. In order to gain the soil nitrogen produced by this fungi, alder roots have specialized structures which the Frankia can live in. The tree provides sugar and energy for Frankia and in return the fungi provides much needed nitrogen to the soil around the Red Alder. Because of this amazing relationship, these trees can colonize nutrient deficient sites long before other arboreal species. In doing so, they cause a buildup in soil nitrogen which allows other trees to successfully establish once the nutrient levels are sufficient, thus the name hero tree. Without them, disturbed sites would take far longer to return to a forested state, and the forest nitrogen cycle would be severely disrupted. In its role as an early succession species, this tree generally has a lifespan of only about 80 years, after which time it is overtaken and shaded out by the coniferous species it helped establish.

In addition to providing critical nutrients to the forest with its symbiotic relationship, the Red Alder has other valuable traits. As a cooking wood it is unrivaled, and has been used for thousands of years by the indigenous people of the region for both cooking and smoking food. It is often readily available on the ground from branch and tree falls and wood was also used in the making of eating implements. It is non-toxic and in fact the inner bark is edible. In contemporary times it has found uses as another of the rare northwest hardwoods, although it is seldom commercially selected for in logging operations and often left behind. As a hardwood it may be used in furniture, but it has also been used in laminated wood production in recent times. Although exceedingly common in many disturbed sites around the city this is the only specimen on the main body of campus. A better view of this species in its native growing habit may be seen in the gully behind the new north campus dorms where they dominate the site having grown in after the last logging of the area and having yet to be outcompeted by coniferous growth.

Native Range: The Red Alder occurs from the panhandle of Alaska south to the Bay Area of California along the coast. Inland it grows in the Cascades of Washington and into central Oregon but not in the Sierra Nevada of California.