An ornamental bunch-grass used in local landscaping has recently become not just pretty, but pretty invasive.
Ravenna grass (Saccharum ravennae), often called hardy-pampas or plume grass, is spreading rapidly from landscaped areas into surrounding riparian areas, and the Southeast Utah Riparian Partnership (SURP) wants the community’s help in controlling it.
Cheryl Decker, the vegetation program manager for Arches and Canyonlands national parks and a representative of SURP, told the Grand County Council on April 15 that Ravenna grass is a newly invasive species.
“We would like to start an education-and-awareness campaign just so people know that it’s actually turning into a big problem and maybe we can voluntarily do something about it, maybe not even remove it from yards but cut seed heads, don’t let it spread, don’t plant it in the first place,” Decker said.
Like many invasive species in this desert area, ravenna grass is out-competing native plant communities, especially along stream beds.
“Riparian areas are really important in this climate,” Decker said. “A lot of wildlife depends on them; we depend on the water. When you get these invasive plants that suck up a lot of water, it hurts everything.”
SURP, a partnership of local, state, and federal agencies, businesses, and nonprofit organizations formed to coordinate restoration efforts along the Colorado River and its tributaries, told the council that it is starting an education and awareness campaign. The Grand County Weed Board was part of the presentation and endorses the campaign.
“For everything we do, we try to educate people, we try to get them to volunteer to do things instead of right now coming and asking the county to declare it as a noxious weed,” said Tim Higgs, the county weed control supervisor.
Ravenna grass has been used in U.S. landscapes since the early 1920s, Decker said. It originates from the Mediterranean and is named after a town in Italy.
“That’s how plants become weedy on other continents, because they come over without their natural predators,” Higgs said.
The spread of Ravenna grass is following a typical growth curve for invasive species.
“A lot of times we introduce new plants in an area and they’re not a problem at all for a really long time, sometimes decades,” Decker said.
At some point, the plant begins to spread exponentially to, what she called in her report to the council, “untreatable proportions.”
“Nobody really knows what that trigger is, but it’s a common occurrence,” Decker said.
This grass is at the early-recognition stage in Moab, where it’s spreading uninvited to other lawns and into sidewalk cracks. However, it is a lot more pervasive in some surrounding areas, such as Mill Creek.
“In Mill Creek, Ravenna grass is growing where there should be willows and other native riparian plants,” Decker said. “This is where I think we’re near the top of the curve.”
The BLM is currently working on an environmental assessment for riparian restoration in the canyon, said Lisa Bryant, the Moab BLM Field Office assistant manager. Also, Moab Solutions will be organizing volunteer groups this summer to help cut the seed heads off of Ravenna grass in Mill Creek Canyon, Decker said. Seed heads form in the late summer.
Other places this grass has also taken root include Negro Bill Canyon, Courthouse Wash, and other Colorado River tributaries.
Although the grass is on noxious weed lists in California, New Mexico, several states on the eastern seaboard, and several National Parks, it is still readily available in many plant nurseries—though not in Moab, Decker said.
Similar situations have played out in this area with other plants, like the tamarisk and Russian olive trees.
“I remember when there where people in the community pushing for Russian Olive,” said Michael Johnson, director of the Grand County Extension office. “As an extension person, I know that the Russian olive literally took decades and decades and decades to get where it is. The fact that nobody controlled it, nobody cared about controlling it for decades and decades and decades, did mean that it became as noxious as, quite frankly, the label on it.”
One of the biggest issues with weeds in this area, Johnson said, is disturbed and uncultivated ground.
“If you’re going to go out there and disturb the ground and you’re not going to actively cultivate it, then you’re inviting weeds,” he said. “If you’re going to have landscapes that have no competition on them, you’re going to be inviting weeds.”
What can keep weeds as bay, at least in town, are things like a competitive lawn and using and replenishing mulches.
”Once you get ahead of the weeds, usually you’re in pretty good shape,” Johnson said.
“Thirsty” ornamental grass crowding out native species
“Ravenna grass is growing where there should be willows and other native riparian plants. This is where I think we’re near the top of the curve.”
Landscape alternatives to Ravenna grass include Great Basin wild rye or giant dropseed, of which there are examples in front of the library.
