This map shows the occurrence of bulbous bluegrass throughout the U.S. on a county level. Only Texas, Alabama, South Carolina and Florida have no reported instances of the invasive grass.
Lindsay Wood and neighboring ranchers have a problem with a pesky invasive plant known as bulbous bluegrass. It’s choking out hayfields, pastures and rangeland in Wyoming, Oregon, Montana and other Western states.
Some infested alfalfa fields aren’t worth harvesting, and no control options seem to work on the grass, says Wood, Arvada, WY.
Introduced as a potential livestock feed in the early 1900s in the U.S., today, bulbous bluegrass can be found in virtually every state. But the most severe infestations are found in the West.
“It’s getting worse and worse all the time,” says Wood. “This stuff has a tendency to establish itself quicker than our normal plants, so it crowds out everything else.”
A former University of Wyoming Extension agent, Wood received a grant to study the grass and is in the first year of a three-year study.
There’s a question whether tilling the grass under in spring is an effective solution, Wood says, because the plant usually comes back quicker and stronger than favored species.
Early grazing has shown some promise, but livestock only find the grass palatable for about three weeks in spring. Then it recovers and spreads.
Interestingly, hay fields left completely alone seemed to fare better than those tilled or grazed, Wood has observed.
“Unfortunately we don’t have a lot of data yet.”
Weed specialist Brian Mealor is also researching bulbous bluegrass; his University of Wyoming Extension findings have been inconclusive, too.
“The difficulty is we’re trying to remove a grass weed from a grass system,” he explains. “Some of the herbicides we’ve screened so far … I’m not too impressed with them.”
Using herbicides to control bulbous bluegrass in alfalfa fields holds some promise, but more research is needed. States with high populations of grass haven’t devoted much effort to manage its spread, Mealor says.
“They have bigger fish to fry. Other invasive plants (such as medusahead) rank higher as a threat.”
Bulbous bluegrass matures early in spring, turns purple in summer and is the only grass species that produces a true bulb.
Typically found in areas that receive more than 12” of precipitation per year, it does grow in drier areas as well. The invasive plant flourishes in high-elevation locations and grows well in areas subject to soil disturbance, such as plowed hay fields, roadsides, field edges and energy development sites. But it also spreads quickly into pastures and rangelands.