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Eight Big Trees at the University of Washington: a self-guided tour

    The University of Washington has quite a collection of trees. It contains over 375 species, cultivars, varieties and hybrids. Because the University has been at this site since 1895, the campus contains some of the oldest and largest trees in Seattle. Unfortunately, in addition to old age, the new buildings and parking structures keep whittling away at the greenery of this lush urban forest. In 1988 alone, 64 trees were removed for the new library site.
    The trees you see on this walk are thought to be the largest specimens of their kind in the state of Washington. If you know of larger specimens, please contact the Center for Urban Horticulture and let us know about them.
    Our walk begins on the west side of the HUB (Student Union Building).

1. CORK OAK (Quercus Suber).
    Location: west side of the HUB, due east of the Alaska-Yukon-Pacific Exposition historical plaque.
    Size: 40 feet tall.
    Notice the foliage and bark of this tree. Unlike our northern oaks, this one has rather small, leathery, evergreen leaves. Instead of dropping them all at once in autumn, it sheds over the year, mostly in the early summer.
    Feel the thick, furrowed, spongy bark. This is the commercial source of cork. In Portugal, the world's leading cork producer, these oaks are periodically stripped of their bark in a manner not to hurt the tree, after they are about 20 years old. Then they are stripped every eight to ten years. The first stripping produces a poor quality cork, but thereafter the tree produces a faster-growing, smoother product. They reportedly can survive this treatment for 100 to 500 years, and grow as high as 85 feet tall.
    Cork oaks are found in at least eight locations in Seattle, and they grow well. They are native to the drier, warmer western and central Mediterranean region. Therefore, when planted in the Pacific Northwest, they need a site with well-drained soil and full sun. The snow storms of January and February 1989 caused major limbs to break, disfiguring the University specimen.

Bay Laurel in 1990

2. SWEET BAY / GRECIAN LAUREL (Laurus nobilis).
    Location: adjacent to north entrance to Sieg Hall; located directly behind the institutional sign that reads "Lee Paul Sieg Hall."
    Size: 40 feet tall.
    Unfortunately, one of the most distinguishing characteristics of this particular specimen are curled, sticky leaves. This blemish is caused by insects, probably psyllids which are related to aphids. Otherwise, this is an exceptionally large, healthy, and attractive example of this bay tree. It is naturally multiple trunked.
    Sweet bay has influenced cooking and language. Crush its leaves; you instantly will recognize the aroma. Laurus nobilis is the original source of bay leaves used in soups and stews.
    And how has Laurus nobilis influenced our language? Since ancient times, a garland of laurel has symbolized victory or accomplishment, hence the phrase "resting on your laurels." An accomplished bard is referred to as a "poet laureate." At one time, men of learning were crowned with wreaths of fruiting laurel; therefore university students were called bachelors, which was derived from the Latin baccalaurus (bacca = berry; laurus = laurel). The Sieg Hall specimen is a male plant and will not produce berries. Learned men were forbidden to marry because it was thought that this would distract them from their studies. Eventually the word bachelor was extended to all unmarried men.

3. DAWN REDWOOD (Metasequoia glyptostroboides).
    Location: northwest corner of Guggenheim Hall.
    Size: 70 feet tall; trunk circumference is 7 feet 9 inches.
    If you visit this tree in autumn you may think it is dying because it will be covered with brown needles. Don't worry, though --dawn redwood is a deciduous conifer. New, soft green needles appear in spring.
    Another distinctive characteristic of the tree is its strongly tapered trunk, buttressed at the base, covered with attractive cinnamon-orange shredded bark. The side branches angle upwards like uplifted arms complete with an armpit-like depression beneath.
    Strong, trouble-free, and handsome year around, dawn redwood has an interesting history as well as excellent landscape value. The genus Metasequoia was first established in 1941 by the Japanese botanist Miki. At that time, it was known only from fossils and thought extinct. But in the same year, a Chinese botanist discovered a living tree of Metasequoia in eastern Szechuan province. This was officially named Metasequoia glyptostroboides in 1948. In December, 1947, seeds were received by the Arnold Arboretum of Harvard University. From there, Metasequoia was quickly distributed to arboreta throughout North America and Europe. Now, almost 50 years later, the tallest dawn redwoods in western cultivation are over 100 feet tall.
    The dawn redwood is closely related to the coast redwood (Sequoia sempervirens), giant sequoia (Sequoiadendron giganteum), and bald cypress (Taxodium distichum). Although there is an 84 foot tall one in Washington Park Arboretum, it has a smaller trunk, only 7 feet 4 inches in circumference.

4. CUCUMBER TREE (Magnolia acuminata).
    Location: northeast corner of the Medicinal Herb Garden along Rainier Vista.
    Size: 78 feet tall; trunk is 5 feet 6 inches in circumference.
    Unlike most magnolias, this one does not have floral splendor. The small, greenish-yellow flowers appear in May after the tree has leafed out and are inconspicuous. Actually, the fruits are more interesting. In the early summer, while still green, the fruits look like small cucumbers two to three inches long, but by fall they have turned dark red and opened to expose red-orange seeds.
    The cucumber tree's leaves are rather bold, five to thirteen inches long and about half as wide. In the spring and summer they are a light-to-medium green, turning a dull yellow in October.
    Though its flowers and autumn color are unspectacular, the cucumber tree's large size makes it a striking sight, even when leafless in winter. This large tree is one of the fastest growing magnolias and is best used as a shade tree for parks and large lawns.
    Magnolia acuminata is native to the Appalachian region and the Ohio and Mississippi river valleys, generally growing on moist, fertile, loose-textured soils. The largest dimensions recorded for it are 125 feet tall and trunks 24.5 feet in circumference. In Washington, this species of magnolia not only is our tallest member of the genus, but also has the stoutest trunk; a cucumber tree in North Seattle has a trunk almost 8 feet in circumference.

5. CRAPE MYRTLE (Lagerstroemia indica).
    Location: Medicinal Herb Garden, east of Garfield Lane and north of Stevens Way.
    Size: 25 feet tall.
    This small tree from China is infrequently planted in the Seattle area. While perfectly hardy, it blooms only when we have a long, hotter-than-average summer. The crape myrtle's affinity for heat makes it a standard landscape item in places such as Texas and California's Central Valley.
    When crape myrtles do flower in Seattle, they are a knockout, being one of the few landscape trees showing vibrant floral color in late summer and early fall. Its petals are crinkled or crepe-like and come in colors of white, pink, lavender, or red. This specimen has raspberry-pink flowers. Just east of it is a smaller one with pale pink flowers.
    Even when crape myrtle does not bloom, it has attractive attributes. Its smooth, peeling bark is a beautiful pinkish beige with light gray mottling; this is especially showy in winter after the leaves have fallen. The foliage starts out with an attractive bronzy tint in the spring, turns glossy green in the summer, and takes on a yellow or bronze color in autumn. Crape myrtles are late to leaf out in spring and to defoliate in fall.
    If you want to grow crape myrtle in the Seattle area, try placing it against a hot southern or western wall, preferably surrounded by pavement that will create an especially warm microclimate. The Arboretum's crape myrtle used to be planted in such a location on the south side of the old Arboretum office, but was moved to the rockrose section in 1984 when construction of the Graham Visitor Center began (and then moved to the Center for Urban Horticulture in 1990).

6. CIDER GUM (Eucalyptus Gunnii).
    Location: southwest side of Bloedel Hall.
    Size: 62 feet tall; trunk is 3 feet 4 inches in circumference.
    As far as is known, this is the tallest eucalyptus in the state. Close on its heels, though, is a specimen of Eucalyptus delegatensis which measures 54 feet tall. The latter tree is located just around the corner on the southeast side of Bloedel Hall. The largest eucalyptus known in Washington State is a Eucalyptus Perriniana located in Seattle's Laurelhurst neighborhood; though only 44 feet tall, it is 49 feet wide and has a trunk circumference of 8 feet.
    There are approximately 500 species of Eucalyptus, most native to the Australian region. They occur naturally in climates ranging from mild temperature to tropical, so only a few can be grown in our area. The cider gum is native to the mountains of Tasmania which experience some of the coldest weather to be found in Australia.
    According to Dr. Stan Gessel, professor emeritus, College of Forest Resources, University of Washington, both of these campus specimens of eucalyptus were planted at their present sites in 1975. This means that they withstood the severe cold of December 1983 and the November 1985 blizzard, but defoliated during the winter of 1988. Whether they will recover fully from this winter's damage is still questionable, but the cider gum looks promising (all of these were removed after the December 1990 freeze).

7. JAPANESE SAWLEAF ZELKOVA (Zelkova serrata).
    Location: along Stevens Way, northwest of Benson Hall and south of the Chemistry Library building.
    Size: 41 feet tall; trunk is 5 feet in circumference.
    The zelkovas are a genus of the elm family (ULMACEÆ). You can notice the similarities in the leaves, which are serrated along the margins and asymmetrical at the base like most elm leaves. In the East and Midwest, zelkova has frequently been planted as a replacement for elms lost to Dutch Elm disease. Zelkovas appear to be much more resistant, though not immune, to this devastating disease.
    As a landscape tree, zelkova's other assets include a fair tolerance to wind, air pollution, and soil compaction. It is free from major pest problems, too.
    Notice the lacy appearance of the exfoliating bark which is common on older trees. The outer bark flakes off exposing an orange-brown layer beneath. The leaves are dark green in summer and turn yellow, orange, or rusty red in autumn. This particular tree turns yellow in late October.
    Zelkova is native to China, Korea, Taiwan, and Japan, where it is a valuable timber tree. A high oil content makes the wood resistant to moisture.

8. WHITE MULBERRY (Morus alba).
    Location: west side of Chemistry Library building.
    Size: 56 feet tall and nearly as wide; trunk is 8 feet 2 inches in circumference.
    The white mulberry is native to China where it has long been used for silkworm culture. In fact, it was introduced to eastern North America in colonial times when attempts were made to establish a silkworm industry in this country. That did not materialize, but the white mulberry did naturalize in the East and South.
    Though uncommon in western Washington, mulberries have been widely planted in drier areas of the West because they are easy to grow and their glossy, handsome leaves provide a quick source of shade; the sprawling suburbs of California are full of fruitless forms of Morus alba. Rank growth, weak wood, and heavy surface roots, though, limit the landscape use of white mulberry.
    This particular specimen is a fruitless form with three main trunks (two now) and attractive bark. If you visit in late October or early November, the leaves should have turned yellow.

(Co-written with Van M. Bobbitt, and originally published with maps and illustrations in the Summer 1989 Washington Park Arboretum Bulletin, pages 10-13.)


Arthur Lee Jacobson plant expert
Arthur Lee Jacobson plant expert
Arthur Lee Jacobson plant expert
Arthur Lee Jacobson plant expert
Arthur Lee Jacobson plant expert
Arthur Lee Jacobson plant expert
Arthur Lee Jacobson plant expert
Arthur Lee Jacobson plant expert
Arthur Lee Jacobson plant expert
Arthur Lee Jacobson plant expert
Arthur Lee Jacobson plant expert
Arthur Lee Jacobson plant expert
Arthur Lee Jacobson plant expert
Arthur Lee Jacobson plant expert

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