The sun rose slowly on its long,
midsummer track across the sky as we sped west on Interstate 90 in South Dakota.
Lush forests, veiled by early morning humidity, fell away to cornfields with
scattered, shady farmyards. At first the corn was thigh high; the ample rains and
early spring allowing it to race past the folk wisdom of “knee high by the 4th
of July.” Then, like going back in time, the corn shrank below the knee-high
goal and ended up at ankle high before petering out into short-grass prairie
with fewer and fewer scattered trees.
The humidity in the air also
disappeared, and despite the vastness of our view over endless rolling hills,
the horizon remained sharp. And on that horizon was a small mountain range with
its tree cover so dark that from a distance the hills looked black. We’d
arrived at the Black Hills.
Suddenly, we were back among trees
again, although dry ponderosa pine woodlands had mostly replaced the lush
deciduous forests. Thickets of willows huddled along creek ravines, with birch,
cottonwood, and bur oak providing a haven for birds. The Black Hills—rising like an oasis out of
the prairie—are a biological mixing place, with species from regions to the
east, west, north, and south.
Swooping upward on a series of
switchbacks, we arrived at Sylvan Lake in Custer State Park. Trading sandals
for hiking boots, and topping off our water supply, we struck out on Trail #9
to Black Elk Peak (formerly Harney Peak), the highest summit in the United
States east of the Rocky Mountains.
The first section of trail was all a
gradual climb. Afternoon sun glittered on shards of mica in the trail dust.
Finally, we began contouring around a ravine, and the trail became flat and
shady. The respite from blazing sun and summer heat was welcome. And we weren’t
the only ones appreciating the Northwoods-like microclimate of this north
facing cul-de-sac. A lush carpet of plants and flowers perched near eye level
on the hillside.
I’d been stumped when trying to identify
many of the dryland plants we’d seen elsewhere in the hills, but here I was
among friends. Wild sarsaparilla spread it compound leaves over little
starbursts of white flowers. Bunchberry was in full bloom, with its pure white
bracts (the showy part of the flower is not even its petals; its big bracts
surround a cluster of tiny flowers) glowing in the shade. And from thick
carpets of dollhouse-sized trailing vines, the pink, paired blossoms of
twinflower gave the forest floor a Lilliputian look.
These little bell-like flowers exist
under the radar of most hikers. They don’t look like much from five feet up. But
they did catch the attention of Carl Linnaeus, the “Father of Moderns Taxonomy,”
who defined our scientific system of naming living things with a genus and
species in 1753. Twinflower was Linnaeus’s special favorite. But although Linnaeus
reportedly was arrogant, and named nearly 8,000 plants during his lifetime, he
refrained from naming any after himself. Instead, he cheekily named beautiful
plants after his supporters and named weeds after his critics.
Linnaeus first named this sweet little
flower Rudbeckia, for two Lapland explorers who knew it well. Later on, he also
applied Rudbeckia to black-eyed Susans, which left twinflower in need of a new
genus. Linnaeus’s friend, Jan Frederik Gronovious, stepped in and named Linnaeus’s
favorite flower after the botanist himself. It became Linnaea borealis.
Linnaeus’s influence circles the globe,
so it’s appropriate this his namesake plant does as well. Twinflower grows
across the northern hemisphere from Sibera to Sweden and across North America. In
Europe, foresters consider twinflower to be an indicator of ancient woodlands. I
often see it across the upper Great Lakes region, and I’ve also seen it in
northern New England. The Rocky Mountains and Pacific Northwest have it, too.
Despite being so cosmopolitan, there’s a definite gap in its range across the
Great Plains. It can’t survive those stark South Dakota prairies.
So how did this tiny little belle come
to be separated east from west? Bunchberry, thimbleberry, wild sarsaparilla,
and more share this disjunct pattern of their populations.
Not long after the glaciers melted, these
plants would have enjoyed the cool, damp climate they prefer across much of the
continent. Then, about 9,000 to 5,000 years ago, the climate warmed. During
this Holocene Climate Optimum, warmer, dryer conditions forced these northern
species out of the arid Great Plains. They were left to survive in the refuges
that mountains and boreal forests still provide. By vining perennially over its
habitat, twinflower is able to exist in isolated microhabitats far from its
strongholds. But climate change has become a significant concern for the
conservation of this species, especially on the edges of its current range.
Although I see it often at home, I felt
a special kinship with twinflower on this hot, arid hike as we both found
refuge in the cool shade of a north facing slope.
Special Note: Emily’s book, Natural
Connections: Exploring Northwoods Nature through Science and Your Senses is
here! Order your copy at http://cablemuseum.org/natural-connections-book/. Listen to the podcast at www.cablemusum.org!
For 50 years, the Cable Natural History Museum has served to
connect you to the Northwoods. Come visit us in Cable, WI! Our new exhibit:
"Better Together--Celebrating a Natural Community" is now open!
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