We were bumping along down the dusty road in Jim’s Subaru when Matt and I realized we needed to pee. Jim peeled off the highway at the next exit, following signs for McDonald’s. When we walked out of the bathrooms he was chatting affably with the polo-shirted teens at the register. Matt hopped up onto a tall stool and I leaned against him, reached up and put my palm on his dense beard. I smiled at the novelty of being in a McDonald’s, at 8:30 in the morning, on a Wednesday, in my hiking boots, with him. Jim appeared with his bounty from the counter, grinning at us from behind his wire-rimmed glasses, and I dropped my hand. He showed us his coffee and his two apple pies, nestled in their cardboard cocoons. Plant survey food.

Back on the road, we drove with the windows down. Jim Malusa, a botanist and research scientist at the University of Arizona, had been making the hour-and-a-half-long trip from his house in midtown Tucson to the Huachuca Mountains in Cochise County every six years since the nineties. He was commissioned by the U.S. Fish and Wildlife Service to survey the population of a rare plant, Erigeron lemmonii, or Lemmon’s fleabane, which is found in only one canyon in the world. This year he’d invited Matt, a grad student who worked his building, and with whom he’d struck up a friendship. Matt had texted me: do you want to come? maybe it would inspire writing?

Matt and I were a month into a breakup that wouldn’t quite stay broken. At the time we were in a good patch, a small sliver of sweetness sandwiched between weeks that stung, then bruised. The end was only a few weeks away, but we didn’t know that then. Until then there was apple pie and the open road and this trip into the mountains, to parse something precarious.

Three hundred fifty million years ago, Southern Arizona was covered in a warm, shallow sea. The climate was different then—balmy and tropical. The vast expanse of water teemed with fish and sharks, trilobites with their pleated exoskeletons slipping fluidly through the water, the delicate flowing fronds of crinoids dotting the seascape like strange feathered flowers. It was in this environment that the Escabrosa Limestone was deposited. The calcareous bodies of microfossils and the skeletal remains of the crinoids fell to the seafloor and compressed over time into a layer of hard, white stone.

Slowly, over hundreds of millions of years, the earth under the continent expanded. Deep basins opened up in the void, then were filled. As the crust compressed and thickened, plateaus rose up, then collapsed. Over time the sea receded and gave way to rivers, followed by giant sand dunes, which were filled in with another sea, which receded yet again. The Huachuca Mountains were exhumed, and with them came the limestone, a graveyard of ancient bodies laid bare. It was on these cliffs that Lemmon’s fleabane found a home. A plant in the sunflower family with a penchant for vertical spaces, it clung to the exposed limestone.

Not much has been recorded about Lemmon’s fleabane and its interactions with humans over time, but other species in the genus Erigeron have long been used for a variety of medicinal purposes by Native people in North America. Spreading fleabane was used by the Navajo to aid in childbirth, for example, according to the Native American Ethnobotany Database, and the Ojibwa people made use of Philadelphia fleabane as a remedy for head colds. It seems unlikely that Sara Plummer Lemmon, the prominent Western botanist, had known or much cared about Indigenous relationships to the species before she and her husband, also a botanist, came across it in 1882. In fact, her papers reveal a deep fear and hatred of the Apache people who lived in the region at the time.

The Lemmons visited the region several times. Wandering among the cliffy outcrops, the canyon walls rising around them, they conducted a plant finding expedition that yielded over forty species never before recorded by white people. A fleabane was one of them, and they named the species Lemmon. The naming, the idea of discovering a peopled place, the colonial instinct to extract and plant a flag—all can be distilled in the way Lemmon’s husband described their excursions in Arizona: a “grand botanical raid.”

A little over a hundred years later, Jim began his work monitoring the fleabane. On the one hand, a raid. On the other, a prolonged expression of care over many years—counting, looking, noticing. He has searched for Lemmon’s fleabane in other canyons with similar characteristics, to no avail. For whatever reason, it sticks tenuously but tenaciously to these spots and these spots only. Jim and other scientists—ecologists, geneticists—know of only around nine hundred fifty Lemmon’s fleabane in existence. Of those, he has selected sixty individuals to be photographed, counted, fussed over. The species holds a Critically Imperiled status with U. S. Fish and Wildlife: “at very high risk for extinction due to extreme rarity.” The entire species could easily be burnt to ash by the wildfires that rage through the canyon. Or crushed underfoot by a group of unobservant rock-climbing bros, or hoovered up by foraging animals, or uprooted and washed away by a particularly raucous monsoon storm, or knocked loose from their careful perches by falling rocks and dashed to the ground. There are so many ways that the fleabane’s story could end.