A mature patch of Ventenata in Gallatin County near Springhill, Mont. Photo taken by Jane Mangold.

First discovered in Montana in the early 1990’s, Ventenata has been steadily encroaching into Big Sky country ever since. This annual invasive grass has been slowly moving eastward across the state and has been recorded in 18 counties.

“If you think of the left-hand side of Montana, Ventenata has kind of been seen in a crescent moon pattern from the northwest to south central Montana,” explained Jane Mangold, Extension invasive plant specialist for Montana State University.

The weed has been found mostly along the I-90 corridor, in Lake, Sanders, Ravalli, Missoula and Gallatin counties to the west and as far east as Big Horn, Carbon and Yellowstone counties.

Ventenata is tricky and is often spotted in unsuspecting rangeland where the land does not have to be overgrazed or disturbed to be an inviting habitat. Additionally, the plant likes to grow among patches of Cheatgrass, so it can often be hard to detect.

Early detection coupled with rapid response is the recommended management approach to Ventenata. Spraying the weed with herbicides is proving to be the best course of action.

If not addressed, Ventenata can actually out-compete Cheatgrass, but unlike Cheatgrass, Ventenata seems to be unpalatable to grazing animals. Studies have shown that Ventenata has three times higher silica content than most perennial grasses, which could be the reason it is avoided.

Ventenata reaches full maturity in late June/early July and can be identified by its open, airy like seed head and bent awns. In the fall when Ventenata starts to dry up, it is a light yellowish-brown, almost straw like in color.

Recently, Ventenata has been petitioned to be added to Montana’s noxious weed list. If officially added, land owners must report the weed and by law they are required to have a management plan in place if Ventenata is found on their property. After a public comment period, it will ultimately be up to the director of the Montana Department of Agriculture to add Ventenata to the official list.

“There is a good chance that by the end of this summer, Ventenata could be a listed noxious weed for the state of Montana,” Mangold stated.  

It is estimated that Ventenata infests more than 55,000 acres in Montana, but that number will continue to grow as more people become aware and learn how to identify it. There are two informational sessions coming up in June for anyone interested in learning more about Ventenata.

The first will take place June 18 in Sheridan, Wyo. This event is hosted by the Northeast Wyoming Invasive Grass Working Group and the tour will discuss topics related to the management and research associated with Ventenata in that area.

Mangold will be teaming up with Mike Jones of the Gallatin County Weed District to lead a Gallatin Valley Land Trust Discovery Walk through Peet’s Hill on Thursday, June 27 at 5:30 p.m. The walk will focus on Ventenata and the threat it poses to Montana agriculture.

Anyone interested in going on this tour must simply meet the group at the north parking lot of Burke Park, located off of South Church Street in Bozeman, Mont. Please visit for more information.

Producers need to take an aggressive, proactive approach to Ventenata, Mangold emphasized. If you suspect you have located a patch of Ventenata, report it immediately to your local county Extension agent or county weed coordinator.