Invasive grass is changing the prairie, maybe forever

Old World Bluestem is turning prairies into monocultures, crowding out other species at an alarming rate.



September 3, 2021 - 11:05 AM

Range scientist Keith Harmoney inspects a research plot that’s being overtaken by Old World bluestem at the K-State agricultural center in Hays. (DAVID CONDOS/KANSAS NEWS SERVICE)

HAYS, Kansas — Keith Harmoney crouches down in a pale yellow field outside his office. He pushes back a cluster of tightly packed two-foot-tall grass, revealing the ground underneath.

In a typical native Kansas grassland, he’d expect to find roughly a dozen different plant species in the square foot of earth between his boots.

“Here, all we see — basically for 10, 11, 12 yards — is just one single species,” Harmoney said. “That’s Old World bluestem.”

The invasive grass has turned this piece of northwest Kansas prairie into a monoculture, where a single species crowds out all the others until it’s the last one standing.

And as it creeps its way across the Plains, Old World bluestem is taking over more and more fields like this one.

Harmoney, a range scientist at the Kansas State University Agricultural Research Center in Hays, is one of the people charged with finding ways to stop it. But he isn’t overly optimistic about his chances.

“It has the upper hand right now,” Harmoney said, “It kind of feels like the Old World bluestem is going to win.”

Decades ago, humans introduced Old World bluestem, or OWB, to this part of the Plains. But some of the characteristics that made the plant an attractive import — its aggressive growth, prolific seed production and hardy tolerance to drought, fire and grazing — are the same ones that make it so difficult to rein in. Once it dominates a field, it’s nearly impossible to eradicate.

Now, Old World bluestem is transforming pastures and grasslands into biodiversity wastelands. Some researchers and landowners are rushing to sound the alarm in hopes of helping more people understand how Kansas can keep this invasive grass from overtaking the state — if it’s not already too late.

Both types of Old World bluestem growing in Kansas — yellow bluestem and Caucasian bluestem — are native to Asia and Europe. And like many invasive species, people brought them to the Great Plains on purpose.

The federal government planted OWB to rehabilitate land after the Dust Bowl. Highway departments have used it to control roadside erosion.

In the latter half of the 20th century, K-State’s research center planted the grass in Hays to study its potential for cattle grazing. The monoculture fields in the surrounding areas today stand as metastasized remnants of those studies.

Even the USDA’s Conservation Reserve Program has encouraged landowners to plant it widely, particularly in Oklahoma and other parts of the southern Plains.

Those purposeful plantings allowed OWB to get a foothold. And the invasive grass took off from there.

“It’s highly competitive,” Karen Hickman, director of Oklahoma State University’s environmental science program, said. “It can outcompete and outgrow — and inhibit the growth of — other native plants.”