The western bunchberry is one of several species of dwarf dogwood, so small that each stem appears but a sprig snipped from the tip of a standard-sized dogwood branch and inserted into the forest floor. Just like its larger cousins, the western bunchberry produces distinctive, showy blossoms in the familiar dogwood form. Each “flower” features four white, asymmetrical bracts, with one opposing pair always larger than the other two. Bracts are not petals, but modified leaves that form part of a floral structure and are often different in color, form, or texture from other leaves. In the western bunchberry, they function similarly to petals, reflecting ultraviolet light that guides pollinators to the plant’s contrasting reproductive parts. The bunchberry’s true flowers are clustered in a cyme1A cyme is a typically flat flower cluster in which each succeeding bud branches from the one before it, beginning from a central floral stem. at the juncture of the bracts. Each individual flower has four petals that are white at the base and tipped with deep purple, a distinguishing feature of the western bunchberry. The upper part of the pistil2A pistil is the female reproductive structure of a flower, consisting of the stigma, which receives pollen, the ovary, in which seeds are formed, and the style, which connects the ovary and the stigma., too, is nearly black. They bloom in late spring through summer, depending on elevation, although a single plant may extend the flowering period by blooming twice in a season.
The relatively tiny buds of the western bunchberry open at one of the fastest known speeds of any flower, which aids in “buzz pollination”. Within the buds, tension between the petals and stamens3A stamen is the male reproductive structure of a flower, consisting of an anther in which pollen is produced and usually a slender filament that attaches it to the flower. An individual flower typically has many stamens. creates pressure, each anther4An anther is a floral organ that produces pollen that contains a plant’s male reproductive cells. Together with the filament that attaches it to the flower, it comprises a stamen. pulled downward against the base of the corresponding petal like the arm of a catapult. An elongated tip on the outer petal of each bud acts as a trigger that is activated at the slightest contact or motion. (Enlarge the accompanying photos to glimpse these hair-like structures.) When mature, the buds pop open forcefully when brushed or even vibrated (for example, by insect wings), releasing the anthers upward and launching a puff of pollen that thoroughly coats pollinators before they visit another flower. This ingenious adaptation may even aid in avoiding predation by pollen-eating insects by obliging them to carry some of it away with them externally as well as internally!
Rarely exceeding 8.0 inches/20.0 centimeters tall, the western bunchberry is a ground-hugging shrub consisting of woody, underground rhizomes5Rhizomes are thickened stems that grow along or under the soil surface and bear shoots above and roots below. that creep through the soil and emerge at the tips as clusters of leaves and flowers. Unlike the rhizomes, these above-ground twigs never branch, giving each the appearance of a single, small plant, but many may be connected by an underground network of branches and roots. Each stem terminates in a whorl of leaves and, often, a single bloom cluster. The whorls typically consist of four leaves on stems that do not produce blooms and six on those that do, although their members occasionally vary by one or two. (Similar to the bracts, whorls on blooming stems have one pair of opposite leaves that is larger than the others.) Beneath each whorl is a pair of much smaller leaves or, occasionally, another less developed whorl. The leathery leaves are evergreen with parallel veins prominently creased into the surface and converging at each end.
As its common name implies, the western bunchberry’s fruits are a tight cluster of round, berry-like drupes6A drupe is a fleshy fruit that contains a woody pit enclosing a single seed. The peach is a well-known example of a drupe. that each contain a single seed. These ripen to a reddish orange and brighten the autumn forest understory until devoured by woodland creatures, which aid in distribution of the seed by passing it through their digestive tracts and depositing it elsewhere.
The western bunchberry is common in moist, even boggy conifer and mixed forests and into the edges of alpine meadows, often on decaying wood and needles. Its range extends from Russia across to Alaska, south to California, and east into Yukon, Alberta, and Montana.
The western bunchberry’s dark flower petals differentiate it from the otherwise similar Canada bunchberry (C. canadensis), a more northern and easterly species it overlaps somewhat in range. Its lower pair of leaves is also typically smaller and more scale-like than that of the Canada bunchberry. However, DNA analysis indicates that the western bunchberry is a unique hybrid of the Canada bunchberry and another dwarf dogwood, the northern, Lapland, or, dwarf bunchberry (C. suecica) of northern Canada and Europe. The northern bunchberry shares much of its western Canada range with the Canada bunchberry but, peculiarly, does not overlap with that of the western bunchberry. How, then, could it have 
given rise to distant progeny? This hybridization is thought to have occurred during an interglacial period of the last ice age and resulted in allopolyploid offspring, each having a complete set of chromosomes from both parents, which enabled the offspring to spread further south than either of their parent taxa, where they speciated into the western bunchberry. (Endemic to subarctic latitudes, Canada and northern bunchberries typically do not tolerate the warm soil temperatures common in southern climes. The western bunchberry, by contrast, has an evolutionary advantage in those environments and thus “moved” over time beyond its parents’ cooler habitat.) For this reason, the western bunchberry’s scientific name is sometimes given as Cornus × unalaschkensis, the “×” symbol the standard botanical notation for hybrids (its name meaning “Cornus hybrid from Unalaska”, the Aleutian island where western botanists first recorded the species’ type specimen). Curiously, although hybridization continues between Canada and northern bunchberries where their ranges overlap, today’s offspring, which unsurprisingly resemble western bunchberries, are not allopolyploid, seldom produce viable seed, and do not extend farther south than the ranges of their parent species. Despite their divergent evolutionary paths, the three species remain linked by another common, “familial” trait: they are the only dogwoods known to employ buzz pollination.
Unusual Specimen
Below is an unusual example of a western bunchberry with eight small, extra bracts. Many in the population at this location shared this unique characteristic that year. Curiously, although the same thriving colony remained a few years later, none showed any indication of additional bracts at that time.
© 2025 Anthony Colburn. Images may not be used or reproduced in any form without express written consent.