Winter Annual Grasses: Ventenata’s Growing Presence

While winter is often a time to slow down and recharge, some plants take advantage of the cooler weather to get a head start on spring. Winter annual grasses, those that germinate in the fall, lie low through the coldest months, and resume growth in spring, are among them. One of the best-known is cheatgrass, but this month we’re highlighting another non-native winter annual that’s relatively new to Madison County: Ventenata dubia.

Ventenata, also referred to as wiregrass, originated from Eastern Europe, Western Asia, and Northern Africa, but was believed to be introduced to North America in the early 1950’s. This grass was first found in Washington and Idaho, and was later documented in Montana in the mid-1990’s. In 2019, prompted by infestations and spread along roadsides, pastures, and native rangeland, Montana listed Ventenata as a class 2A noxious weed. This classification means that the plant is common in isolated areas of Montana, and that their management (either containment or eradication) will be prioritized by local weed districts. While it hasn’t spread aggressively across Madison County, the Madison County Weed District reports confirmed patches in the Bear Trap area on the east side of the Madison River.

Ventenata typically grows around 6-18 inches tall and has thin wiry stems, hence it’s nickname ‘wiregrass.’ The stem also has reddish-black notches along it, with seed bearing stems coming off the main stem at almost 90-degree angles. From late May through June, the open, airy, pyramid-shaped flowering structures called panicles emerge, and the stems stiffen. When mature, Ventenata often has a yellowish tan color or remains green.

Ventenata usually germinates in the fall, staying dormant in the harshest parts of Winter and resuming growth in the Spring. In Montana, you are most likely to find Ventenata in rangelands, forests, open spaces (ex. parks), and roadsides. Although it often grows alongside cheatgrass and Japanese brome—and can resemble them from a distance—there are key differences. At the seedling stage, Ventenata should look thinner and more needle-like compared to cheatgrass and brome which often appear twisted and hairy. Ventenata seedlings also emerge later than the other two grasses. Cheatgrass and Japanese brome also tend to have droopy panicles whereas Ventenata’s remain upright.

So why is Ventenata so concerning? Like other invasive species Ventenata has had substantial economic and ecological impacts in native grass habitat. The grass is not toxic; however, it has a high silica content and is generally unpalatable for wildlife and livestock. If the grass were to take over rangeland and pastures outplacing native grass, the forage would be minimal. Dense Ventenata patches also have the potential to pose a risk related to wildfires. Their lifecycle means that they dry out earlier than native grasses, possibly providing fuel during fire season. Additionally, its shallow root system stabilizes soil far less effectively than native species, making areas more vulnerable to erosion.

As far as management is concerned, the best ways to control the spread of Ventenata is to maintain healthy stands of native perennial grasses and prevent spread. The grass seeds can easily attach to clothes fur and machinery, so when recreating be cautious of picking up any stowaways and clean your gear or yourself before leaving the recreation area. If possible, try and throw the grass seeds in a secure container, rather than employing the ‘pick-and-flick’ method of seed disposal. If introduced somewhere new, a healthy landscape is more apt to prevent establishment of invasive intruders. Early detection of infestations is key to help control Ventenata. Researchers have also experimented with chemical control of Ventenata using herbicides with the active ingredients indaziflam, imazapic, sulfosulfuron, and rimsulfuron.

If you’d like to learn more about identifying and managing invasive annual grasses, join the Madison Conservation District, MSU Extension, and the Madison Valley Ranchlands Group for the final event in their free Rancher Roundtable series this winter. The session on February 26th will feature an interactive grass identification workshop led by Dr. Jane Mangold. Attendees are eligible for one pesticide credit! A taco bar from Nachos Mamas will also be provided for lunch. For more information or to RSVP, reach out to the Madison-Jefferson Extension Office at (406)287-3282 or MadisonJefferson2@montana.edu.