Inflorescences of Cornus unalaschkensis
Coastal bunchberry, western bunchberry, or Alaskan bunchberry, is native to western North America and extreme eastern Russia. According to the Flora of North America account of Cornus unalaschkensis, the species inhabits “maritime copse or heath, maritime coniferous forests and bog woodlands, moist broadleaf or coniferous forests” from elevations of 0 to 3000m (to 10000 ft.).
This entry is a companion to one from a decade ago for the similar-in-appearance Cornus canadensis. However, one of the key morphological differences between the species is visible in both entries; Cornus unalaschkensis has petals that are at least partially purple, while Cornus canadensis has white to greenish-white petals. Do note that the inflorescence for each of these species is a pseudanthium (“false flower”), in which a cluster of small flowers (or florets) forms what appears to be a single flower. In this instance, the 3 clusters of purple-tinged florets are each subtended by 4 white involucral bracts that have the appearance of flower petals.
Once you know this as a difference between the two species, they become relatively easy to distinguish when in flower. Geography is a clue as well; Cornus canadensis tends to occur from the Rockies eastward, while Cornus unalaschkensis tends to be more associated with the coast even within its broader western North American / eastern Russian range. In local horticulture (and even in some field guides), Cornus unalaschkensis will sometimes be ignored in favour of Cornus canadensis; it always makes me frown when I encounter Cornus canadensis on local “recommended native plant lists” instead of the true local native, Cornus unalaschkensis. An overreaction, perhaps–as a transplant to Canada’s west coast from the native range of Cornus canadensis, I’m sure I wrongly assumed its identity as well, until corrected by a reference like Plants of the Pacific Northwest Coast.
The so-called explosive pollination is an interesting feature in the buncheberries. Ted Mosquin (any relation to you, Daniel?) described it in Canadian bunchberries (Cornus canadensis):
“As the bud and the pollen mature, slits are formed on the abaxial surfaces of the anthers. At this stage both the reflexed tip of the filament as well as the petals come under a powerful tension which is released only when the pop mechanism is triggered. During the “popping” the arched tips of the filaments act as elbow springs and the four anthers snap upward. The “popping” of the flowers occurs so rapidly as to be scarcely perceived by the naked eye even through the microscope. After popping, the stamens assume a more or less vertical position and appear to be empty of pollen. Pollen grains are light yellow in colour and slightly sticky; they are too large and heavy to be carried away by the wind.”
See http://bomi.ou.edu/ben/ben194.html
Cornus unalaschkensis is an allotetraploid species that originated from the hybrid of Cornus canadensis x C. suecica.
See Bain, JF and KE Denford. 1979. The herbaceous members of the genus Cornus in NW North America. Bot. Not. 132:121-129.
Yes, Ted is my uncle.
Being from the U.S. East Coast, I was only familiar with Cornus canadensis, the specific epithet meaning of/from Canada.
Cornus unalaschkensis expanded my knowledge of geography, as Unalaska is one of the Aleution Islands of the U.S. state of Alaska that I ,for one, had never heard of before this!
Thank you for your helpful hints for distinguishing between these two species.
Youtube: Exploding Bunchberry at 10,000 FPS
Here is a link for Eleanor Ford’s suggested video: https://www.youtube.com/watch?v=aFR17bX0noI
I’m another person who wasn’t aware of the two species. Also a transplant from the east to the Pacific northwest, I assumed I was looking at the same plant I’d seen in New York. I’ll be on the lookout now, for that bit of purple. I checked my photo files and found a C. canadensis photo from the Adirondacks; the true petals are creamy white. A photo of what must be C. unalaschkensis, taken at Big Four Ice Caves in the North Cascades on June 1, 2014, shows a dark purple center.
A tendency this plant has that sticks in my mind, is a delightful habit of growing against different surfaces so it forms a blanket – more than a ground cover – e.g. it “climbs” up stumps and spreads around them in a very artistic manner. It’s a charmer!
This is such a lovely plant. Thanks for all the info about it and the great video of the “exploding” pollination.
The Eastern C. canadensis is one of my favorite natives here, in New York. It’s nice to see it’s charming cousin.
Thanks again. I love this site.
Hi Daniel,
I seem to remember that the two species differ in ploidy level also. Isn’t C. unalaschkensis a polyploid?
These postings are much appreciated.
Yes, that seems to be the case.