JoAnne Skelly: Is pampas grass a problem?

My friend Paul asked me to write about pampas grass, Cortaderia selloana, which in some parts of the country has become a problem invasive plant. While it is not on the noxious weed list (listed as noxious by law) for Nevada or California, Nevada plant ecologists consider it potentially invasive in the Las Vegas area and the California Invasive Plant Council has categorized it as a “high” threat to the state’s wildlands. It can totally alter a native plant community decreasing nesting sites and food sources for native animals.

Many coastal habitats in California are infested. It is listed in the Invasive Plant Atlas of the U.S. Texas, Louisiana, South Carolina, Hawaii and Utah all consider it an invasive species. Other parts of the world that have been infested include Australia, New Zealand and South Africa.

Pampas grass has been widely planted as an ornamental grass in areas where the average annual extreme low temperature is not less than zero degrees Fahrenheit. This native of temperate South America has been a popular plant since the Victorian Era. With its 8-foot tall feathery plumes and its dense clumping growth, it is easily recognizable. It has been grown commercially for its plumes.

This grass is a prolific seed producer with each flower head producing up to 100,000 seeds. Its seeds are easily spread by wind up to 20 miles away. Another way seeds are spread is by people cutting the plumes for flower arrangements and then transporting them (and their many seeds) to a new area, happily spreading seeds along the way.

It can also propagate from its roots that can spread out 13 feet while reaching a depth of over 11 feet. Where conditions are right: sandy soils, ample moisture and sun, this plant can become very invasive. It has the ability to form dense stands that quickly become a high fire hazard.

Paul has seen pampas grass in the Carson area. I wonder if it has survived through any of the really cold winters where temperatures dip as low as the minus 20s. This doesn’t happen often, and may happen even less with global warming. Although our cold winters should keep this plant in check, why risk planting something that has the potential during warmer cycles to invade our stream banks, rivers and lakes destroying our native habitats? There are other grasses, such as Calamagrostis x acutiflora ‘Karl Foerster,’ that are less risky options.

JoAnne Skelly is Associate Professor & Extension Educator, Emerita at University of Nevada Cooperative Extension. She can be reached at skellyj@unce.unr.edu.