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Ladies’ Tresses Orchids:
The Nose Knows

Ladies Tresses Orchids

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 simplify matters.

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