Botanical musings by Green Everett Partnership Forest Steward, Sara Noland
Riding the bus from my home in Everett to my job in downtown Seattle, I’ve had time to notice how many flowering dogwood trees grace the forested strip along I-5. Spring is the time when our native Pacific dogwood (Cornus nuttallii) shows why it is a beloved garden plant as well as a beauty of the forest. Its white blooms glow against the dark backdrop of Douglas fir along the freeway. We’re fortunate in western Washington to have not one but three native “dogs” to enjoy. In addition to the Pacific dogwood tree, there’s a native dogwood shrub (Cornus stolonifera or C. sericea) and a ground cover (C. canadensis).
The family Cornaceae has anywhere from 40-plus to over 60 species depending what book you read. Numerous horticultural varieties have been developed over the past century. For an interesting overview I recommend “Dogwoods,” a book by Paul Cappiello and Don Shadow with photos of both our native species and the ornamental types. What the species in this family share are opposite branching; oval to pointed leaves with pronounced veins running parallel to the leaf edge; umbrellas of small yellow or greenish flowers; and berry-like fruit (drupes). Wait—aren’t dogwoods known for large, showy flowers? The “flowers” of C. nuttallii that I see from the freeway (and those of C. canadensis, on a smaller scale) are actually bracts or modified leaves. The true flowers of these species are clustered like a green or yellow button in the center of the bracts. C. stolonifera lacks the modified bracts of the others and instead has more subtle clusters of white flowers.
Pacific dogwood (Cornus nuttallii) is a graceful tree also known as western flowering dogwood. It typically occurs singly or in small groups in moist, shady forests west of the Cascades, ranging from Vancouver Island south to California (only small populations are known from east of the Cascades). Tree height is generally 25 to 50 feet. The oval leaves are 3 to 5 inches long, with blossoms (including bracts) up to 6 inches across. While ornamentals of the eastern flowering dogwood type (C. florida) typically have only four bracts, Pacific dogwood often has six or more per bloom. Flowering occurs in spring (this year, late April to mid-May) and sometimes again in fall. Fruits ripen to a red cluster of “berries.” Around 1980 an introduced fungal disease called dogwood anthracnose (Discula destructiva) invaded C. nuttallii populations in Washington. Healthy trees appear able to survive the disease, and there are numerous sources of advice for how to keep a native dogwood tree happy in your yard. Coastal indigenous groups traditionally use Pacific dogwood charcoal for tattooing; the wood for harpoons, knitting needles, and other implements; and the bark for making rope or brewing into a dye or medicinal tonic.
Red-osier or red-stem dogwood (Cornus stolonifera or C. sericea) is a hardy shrub, common to moist areas, that’s a superstar among forest stewards. It can form dense thickets over 10 feet tall, and it spreads readily by sending out side branches that root in moist soil. Fortunately it thrives on pruning, and the cut stems can be used for live staking, making it a favorite for restoration projects along streambanks and wetlands. I’ve observed the stems to range from bright red to maroon to greenish. Flower clusters are 2 to 3 inches across and usually appear in the spring around the same time as Pacific dogwood. I’ve watched American robins consume the whitish-blue fruits from the red-osier dogwood in my front yard, and its many-branched habit also creates excellent resting spots for winter flocks of chickadees, juncos, and other small birds. Red-osier dogwood ranges across temperate and higher elevation areas of North America, again favoring moist to seasonally wet areas. Coastal Salish Tribes traditionally use the flexible branches for salmon skewers, basket rims, and fish traps, and the bark can be made into cordage.
Our native ground cover dogwood (C. canadensis) is known as bunchberry, bearberry, or other common names. A swath of bunchberry in bloom reminds me of a miniature forest of dogwood trees, only about 10 inches tall but with four showy white bracts against dark green leaves. It is also a wide-ranging species native to Alaska and the northern United States, but unlike red-osier dogwood it’s a rather finicky plant. I’ve tried several times unsuccessfully to establish bunchberry in my garden—I think my space lacks the cool temperatures and highly acidic soil needed to keep bunchberry healthy. Blueberry farmers in Maine have the opposite problem, where bunchberry is a prolific weed in their fields. This is a species I’m always excited to find because it seems to be rather uncommon in our area; when I do find bunchberry it’s usually a small patch in a moist mixed forest. Coast Tribes traditionally eat the bright red fruit of bunchberry with grease or (more recently) sugar.
A last word about bunchberry: Scientists studying the flowers of this plant found its stamens to be like miniature trebuchets capable of catapulting pollen 2.5 cm into the air, which doesn’t sound like much unless you know that’s 10 times the height of the flower. The flower’s explosive opening—in a fraction of a second—is thought to be the fastest movement recorded in any plant. Researchers believe that launching pollen into the air at high speed in this way both propels it into the wind and makes it stick onto visiting insects, both strategies for more successful pollination.
Arno, S.F., and R.P. Hammerly. 2007. Northwest Trees: Identifying and Understanding the Region’s Native Trees. The Mountaineers Books.
Cappiello, P., and D. Shadow. 2005. Dogwoods: The Genus Cornus. Timber Press.
Edwards, J., D. Whitaker, S. Klionsky, and M.J. Laskowski. A record-breaking pollen catapult. Nature, May 12, 2005, p. 164.
Pojar, J., and A. MacKinnon. 1994. Plants of the Pacific Northwest Coast: Washington, Oregon, British Columbia, and Alaska. B.C. Ministry of Forests and Lone Pine Publishing.
Whitaker, D.L., L. A. Webster, and J. Edwards. 2007. The biomechanics of Cornus canadensis stamens are ideal for catapulting pollen vertically. Functional Ecology, Vol. 21, No. 2, April 2007, pp. 219-225.