In a typical Great Basin shrubland, forbs and grasses grow patchily underneath a canopy of well-spaced shrubs like sagebrush and shadscale. That new weed would drastically change the region's fire ecology, among other things. As Aldo Leopold wrote in the 1949 classic A Sand County Almanac, "One simply woke up one fine spring to find the range dominated by a new weed." The weed hitchhiked from Europe in contaminated seed, straw and ship ballast, and crisscrossed the West with the railroads, which spread it with the straw used for livestock. That was a shock to native bunchgrasses like Poa and Indian ricegrass, which, in that part of the West, had evolved in an environment unused even to bison. Western settlement had brought widespread livestock grazing to the Great Basin, a Texas-sized area that covers 180 million acres in southeastern Oregon, southern Idaho, western Utah and Nevada. The ancestors of Leger's beloved Poa first encountered cheatgrass, a native to parts of Europe and Asia, in the late 1800s. Determined to show me its root structure, Leger finally pulls the demonstration plant out of the ground, sacrificing it for the sake of knowledge. "Cheatgrass (also) has super-fine roots and this is about the only native plant I've ever seen that has the same sort of roots." That allows the Poa to take up space and use nutrients the weedy invader would typically claim. "I don't want to kill him, but it's instructive to do that because his roots are super fine and they go out really shallowly, all through this area," she explains, gesturing at the bare circle. Leger scoops away the soil around its base, digging carefully underneath it. "We did some trials to see what native perennials were the most competitive with cheatgrass, and it was this guy," says Leger. Around the little Poa though, there is no cheatgrass at all, just a foot of bare, pebbly dirt.
This is not surprising the Great Basin is a disturbed landscape, and cheatgrass is now its dominant inhabitant. The ground around us is covered with the invasive annual Bromus tectorum, also known as cheatgrass. It's early May, and Leger, graduate student Owen Baughman and I are crouched on Peavine Mountain, a scrubby rise near the University of Nevada, Reno, where she is an associate professor of plant ecology. It is, she tells me, a "cute" native called Poa secunda. A tiny, energetic woman in her mid-30s, Leger hovers, bee-like, over a teensy grass with blue-green blades. This guy is lovely!" ecologist Beth Leger exclaims, falling to her knees. Native plant growers face many challenges