Surrounding the basketball court next to Star Hall, around the Center Street Gym and in yards around Moab, tall feathery plumes of the common ornamental plant known as ravenna grass bob in the wind. Though beloved by landscapers, ravenna grass has escaped to Mill Creek and other streams, where it is crowding out native plants, local official say.
Ravenna grass (Saccharum ravennae), also known as hardy pampas grass, is a Eurasian relative of sugarcane that can grow up to 12 feet tall. One plant can produce hundreds of thousands of seed heads, according to the Southeast Utah Riparian Partnership.
Cheryl Decker, former vegetation program manager for the Southeast Utah Group of the National Park Service, said ravenna grass has become a problem in streams and rivers throughout the Southwest, including in the Grand Canyon and along the San Juan River.
Ravenna grass was brought to Moab by gardeners at least 25 years ago, said Kara Dohrenwend, founder of Wildland Scapes and the nonprofit Rim to Rim Restoration. Through Rim to Rim, Dohrenwend and others work on projects including removal of “invasive species” like ravenna grass. The term “invasive species” is used to describe an organism that spreads to a new area and negatively impacts the local environment. Not every non-native species becomes invasive.
The population of ravenna grass in the Moab area has grown quickly in the past five years, according to Dohrenwend, who has seen ravenna grass spread up Mill Creek above the power dam, into Negro Bill Canyon and near the Castle Valley turn-off from state Route 128.
“It’s becoming much more common — it’s just everywhere,” Dohrenwend said. “That didn’t used to be the case.”
On a larger scale, invasive plants have a big impact. According to the National Wildlife Federation, approximately 42 percent of plants listed as endangered species are in trouble chiefly because of invasive species.
“When [invasive species] come in, they crowd out the native ecosystems and that can mean a lot of things. That can mean there isn’t enough food for birds or other kinds of wildlife,” said Decker.
In particular, Ravenna grass chokes out the plants that usually shade streams, she said. With less shade, the water gets warmer and it becomes more difficult for fish to survive.
Decker said an invasive species may be present at a low level for a long time and then suddenly become much more common, as it appears Ravenna grass is doing now.
For this reason, Decker said, when it comes to weeds like ravenna, “if you can get them earlier then it’s not nearly as expensive or as detrimental to the environment.”
The BLM is working with the Grand County Weed Department to start controlling ravenna grass in Mill Creek Canyon using targeted herbicide applications, according to Ann Marie Aubry, a hydrologist at the BLM’s Moab Field Office. The agencies scheduled two days for ravenna control in the canyon in September, but canceled both due to weather. Aubry told The Times Independent that the two groups plan to schedule another workday in the next several weeks as weather permits.
In 2014 and 2015, the Mill Creek Partnership, a collaboration between the BLM and the nonprofit Moab Solutions, cut seed heads off Ravenna grasses in the Mill Creek area to prevent the plants from spreading, said Sara Melnicoff, founder of Moab Solutions.
Next year, the BLM may begin digging out ravenna grasses that are too close to the creek for safe herbicide application, according to Aubry.
“We could potentially catch it in the beginning before it’s so big we can’t even imagine how we’re going to deal with it,” Aubry said.
While other invasives like Russian olive may never be fully eradicated, with ravenna, Aubry said, “it seems possible if we start now to keep it under control.”
Melnicoff recommended that Moab residents dig out any ravenna grasses growing in their yards. Until the grasses are removed, it is best to cut off any seed heads, wrap them in plastic bags and throw them away to keep the seeds from dispersing she said, adding that seed heads may have to be cut several times a year.
“These plants are beautiful but they don’t belong here.” Melnicoff said. “They were introduced and they’ve taken over.”