Meet Your Neighbors
Ladies’ Tresses Orchids:
The Nose Knows
Photo: David Schwaegler
As summer days fade into fall, a surprising late-blooming orchid shows up
in the Chicago Wilderness area: the white, spiraling flowers of ladies’ tresses,
also known as Spiranthes orchids. Although several other members of the
genus live in this region, nodding ladies’ tresses (Spiranthes cernua)
and Great Plains ladies’ tresses (Spiranthes magnicamporum) are the most commonly seen.
Visitors to local wild places generally encounter Spiranthes in higher-quality
prairies, as well as in healthy fens and sandy habitats. Both Spiranthes
cernua and Spiranthes magnicamporum grow between 8 and 24
inches tall, with two to three dozen small, white flowers that spiral up a stalk growing
above the plant’s long, narrow leaves; the entire effect is like a stiff braid of green rope
sprouting white flowers.
Spiranthes cernua and Spiranthes
magnicamporum are so similar in appearance that even expert taxonomists have difficulty telling them
apart. Just over 30 years ago, in fact, S. magnicamporum didn’t even technically exist as
a species. Through detailed genetic studies in the 1970s, graduate student Charles Sheviak was able to confirm
the plant’s distinct identity from its look-alike.
“Spiranthes are among the toughest orchids to identify,”
says Marlin Bowles of The Morton
Arboretum. “It may be making an evolutionary jump, currently.”
That individual cernua plants can have different forms doesn’t
There are small clues to separate the two Spiranthes. Cernua usually begins to bloom
in mid-August, while magnicamporum flowers slightly later, in early to middle September. Cernua
usually still has its leaves by the time it flowers, while magnicamporum loses all its leaves. Bowles
also notes that cernua prefers wetter habitats than magnicamporum, and is self-pollinated
instead of pollinated by bees like magnicamporum.
But amateur naturalists need only take one simple piece of equipment into the field to distinguish between
the two species, and it happens to be mounted on their faces. When searching for S. magnicamporum orchids,
“you just follow your nose down,” says Liz Aicher, an orchid monitor in Kane County.
“If there are enough of them, you can smell it when you go into a prairie,” says Cathy Bloome,
an orchid monitor in Lake and Cook Counties. Bloome describes the scent as similar to vanilla. Others have
described it as smelling like almonds. (Some older, wiser readers may be able to detect the compound likely
responsible for the scent: coumarin, a nature-derived flavoring used in food until the 1950s and more recently
as a somewhat controversial scent in tobacco and perfume. It was found to cause liver damage, and now also
serves as a component in rat poison.)
S. cernua, in contrast, has a much fainter smell. Steward Barbara Wilson sums it up pretty well:
“Uphill in dry places, Spiranthes has a scent; downhill in the damp, it doesn’t.”
Orchid experts say the populations of these two Spiranthes species are doing relatively well in the
Chicago Wilderness area. “Cernua makes itself at home in many of the moist sand prairies along
Lake Michigan,” says Bowles. “Magnicamporum, meanwhile, has actually been introduced in
some prairies that are being restored and can grow up in just a couple of years,” says Bloome.
“S. magnicamporum is the quickest orchid to grow from seed. It usually comes into disturbed
areas quite quickly.”
Locally, Bowles recommends looking for the orchids at Illinois Beach State Park. There, he says, “you
may also run into S. gracilis, which wears a bright green spot on the lip of its flower.” Happy
trails, and happy smells.
— Allison Knab