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Two teams scoured the Big Horn Mountains in the summer of 1979 looking for the undiscovered. They weren’t working together, and neither knew what they would find.

But on back-to-back days, Wyoming botanists Robert Dorn and Ronald Hartman each collected samples of the previously unrecorded Hyatville milkvetch.

“I was surprised to see that kind of material there because I had seen them in the southwest part of the state,” Dorn said. “It looked like the same species, but there were some minor differences I could see right away, so I had to take it back and study it some more to make sure it was different.”

It was. And the Hyatville milkvetch, with its white and purple flowers and red and purple papery pods became one more plant unique to the Cowboy State. But unlike some flowers that may grow in swaths of countryside in Wyoming, the Hyatville milkvetch grows exclusively in two populations near the tiny mountain town.

That’s the thing about milkvetches: They are the largest genus of wildflowers in Wyoming and part of the bean family, which is one of the largest in the world. But while some species, such as the tufted milkvetch, are widespread across most of the state, others, like the Hyatville milkvetch, are incredibly restricted.

It’s one of the many things that makes the genus so interesting, said Bonnie Heidel, lead botanist with the Wyoming Natural Diversity Database at the University of Wyoming.

The Dubois milkvetch, among other plants, will also be a focus of the Wyoming Native Plant Society’s annual meeting June 17-19 in Dubois.

Dubois taxidermist and amateur botanist Lynn Stewart first found the rare plant on a ranch outside of town.

“I sent some pictures to a friend who is a botanist and she said ‘Wow, you saw Dubois milkvetch, where?’” he said. “She knew where some colonies were and this was not one.”

Experts realized populations of the small plant with purple flowers appear over large portions of the Dubois Badlands.

“There are other plants that look like it at other times of the year,” Stewart said. “But it is very obvious when you know what you’re looking at.”

Of the 80 kinds of milkvetch, 17 are quite rare, and some of them can be found only in Wyoming. All but two of the 80 flowers are native to Wyoming.

“Many of the milkvetches are found on the plains but there are also different ones from mountains to alpine and to wetland margins,” Heidel said.

They can vary greatly in appearance. Some grow knee high, others hug the ground in low mats or mounds. Flowers can range from white to pink to purple. But all of them can be discerned by their bean-like pod structure.

All plants also have wing petals – the pair of petals on either side of the flower – that look like the outline of insect wings, Heidel said.

“This is part of the cue that insects get on which plants have the rewards that they seek,” she said. “They might think they’re mating with another insect when they go in for nectar.”

Dorn doesn’t have clear memories from that day in 1979. He’s discovered a couple other milkvetches in his time in Wyoming.

When he collected the sample, he made a mental note to check on its rarity. It wasn’t until 1988 that he described the new flower officially in his book, “Vascular Plants of Wyoming.”

And after decades of studying rare, common and unique Wyoming plants, Dorn is often still drawn to the milkvetch.

“They’re a lot more interesting than a lot of things,” he said. “They have nice flowers and grow in unusual places. The unusual ones are usually on a particular rare type of geological formation. The Hyattville is on the red beds, an area that’s pretty barren as a rule.”

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