Behold: A Frozen Rare Plant

Wyoming’s desert yellowhead (Yermo xanthocephalus) is the rarest of Wyoming’s four listed threatened plants.

It seems odd that any monitoring can really be done in a foot of snow, but not every state can be geographically located to have sunshine 360 days a year. While other states would likely call it quits the minute the precip charts start to stir (looking at you California), leave it to Wyoming to put on the gaiters and saddle up (yee-haw). And so, with a foot of snow on the ground, off we went into the badlands of Wyoming to monitor cheatgrass at one of the county’s only documented Yermo sites.

What in the world is Yermo? Nobody knew until 1990, when Robert Dorn, Wyoming’s very own resident plant expert, discovered the first population. When Dorn first came across the plant in spring he suspected it might be a new species of milkweed based on its leathery leaves and waxy yellow buds. When he returned to collect it in June he was surprised to find that the plant was actually a member of the sunflower family (Asteraceae or Compositae) and not a milkweed at all! He noticed that the floral bracts were quite unusual in being bright yellow rather than green and leafy as in 99% of all other composites. Dorn realized that he had not only a new species, but also a new and undescribed genus. The plant was given the the name Yermo xanthocephalus by Dorn in 1991; yermo meaning “desert” in Spanish, and xanthocephalus translating as “yellow head”.*

Still, desert yellowhead remains known only from Dorn’s original population, despite extensive searching for suitable habitat. It was listed as threatened by the U.S Fish and Wildlife Service under the Endangered Species Act in 2002.Today it is known as the rarest of Wyoming’s four listed endangered plants, being known in Fremont County, WY and nowhere else.

So you might understand why, even with a foot of snow on the ground, I was pretty excited to head out and uncover this thing. We hiked about a mile in and as we approached, I realized that I wasn’t dressed for the occasion. As we got closer our target area, at the foot of a large butte, my feet and ankles slowly began to freeze and I had vague visions of my mentor hauling me out, my embarrassment surpassed only by the disappointment of not getting to see the plant. But thoughts of my frozen limbs disappeared when I heard her excited shout. How she could find and recognize this remarkably rare plant in all the snow was beyond me, but I wasted no time asking questions and rushed over to behold the plant for myself.

Approaching the Yermo population

What I saw was akin to a frozen plant skeleton. Completely unspectacular and unremarkable in any way to the untrained eye. Partially buried in the snow, the plant had one to five stems up to 1 foot tall. Its leaves were alternate and slightly oval to lance shaped about 1 1/2 to 10 inches long, and often folded at the midvein. I learned that the plant grows new shoots each year from an overwintering taproot and usually begins flowering in late June and continues to flower over the entire growing season. Its unique among Wyoming composites in having bright yellow floral bracts that resemble a series of fleshy bananas, although it all looked dead and brown when we saw it.

Not much to look in the winter, but this little guy is actually doing pretty well here!

No one knows how long desert yellowhead can live. Long term studies have shown that population numbers fluctuate from year to year. We visited this population to monitor cheatgrass observed nearby. Although no cheatgrass was found among the plants, we did find some nearby. This could be worrying because cheatgrass is invasive and if established, could outcompete this delicate population. Management decisions today could easily influence this threatened species.

Its easy to see how this little plant could easily get overlooked and why some might question large efforts to remove and control invasive grasses in areas where no cattle grazing exists, however the BLM recognizes that plant conservation and protection is essential to sustain the ecological, economic, and aesthetic values of our public lands. For this effort, the Wyoming BLM is preparing a desert yellowhead conservation strategy in coordination with local, state, and other federal agencies.

No Yermo up on top, just amazing views!

Now that my season is wrapping up, I’m looking forward to the next adventure. In two weeks I’ll be leaving for Sacramento, where I’ll be working with the Bureau of Reclamation on water use policy. It’ll be important to remember all the pieces in the puzzle. From the many sagebrush all the way to the lone Yermo.

Gwen Robson, Lander BLM

* Bureau of Land Management. “Wyoming’s Threatened and Endangered Plant Species: Desert Yellowhead”. U.S. Department of the Interior.


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