Text and photos by Noreen Hannigan, unless otherwise noted.
Yes, grass seeds are blowin’ in the wind, but they’re not necessarily producing a pretty song! The list of non-native invasive grasses that escape cultivation from yards and gardens keeps growing. The 2022 edition of Plant Invaders of Mid-Atlantic Natural Areas, Field Guide by Jil M. Swearingen and Judith P. Fulton characterizes invasive plants as “an invading army” that can spread rapidly to take over natural ecosystems and be “difficult if not impossible to eradicate” once introduced and established over wide areas.
What Kinds of Grasses are Considered Invasive and Why Is This a Problem?
Because many of the plants in local yards and for sale in garden centers evolved elsewhere, under different conditions, they no longer have the kind of competition to control their spread that they would have in their original setting. They therefore have the freedom to run amok away from their homes (like teenagers on spring break). They multiply rapidly and can displace native plants, form monocultures, and thereby eliminate sources of good-quality nutrition for our year-round and migrating wildlife. Some also release chemicals into the soil that inhibit the growth of other plants, or hybridize with native plants, which alters those plants’ attractive qualities for wildlife. These are just a few of many ways invasive plants degrade the ecosystem, which leads to populations of animals, birds, and insects (both in the young and adult phases) going into decline due to scarcity of food from the native plants on which they depend. This, in turn, robs the entire planet of biodiversity. Note that all of these plants are fine as long as they stay where they evolved. And in turn, some plants from our region have been introduced overseas and are invasive in other places for the same reasons the non-natives here are a problem. It’s all about keeping plants and wildlife where they evolved and not, as the saying goes, “moving puzzle pieces around.” Ecosystems take millions of years to evolve and moving a plant halfway around the world in a day’s airplane ride happens way too fast for an ecosystem to adapt.
Back to the newly revised Plant Invaders field guide, though, I noticed while I was thumbing through it that it includes almost double the number of invasive ornamental grasses and sedges than previous editions. One new entry in this field guide is Chinese fountain grass, Cenchrus purpurascens. (It actually goes by a couple of Latin names, including Pennisetum alopecuroides. And—no surprise—it goes by more than one common name, too, but more on that in a moment.) This non-native grass is widely available for gardeners, usually with no mention that it can escape gardens and invade natural areas, with detrimental consequences, so it’s important to have our antennas up when we are visiting garden shops.
I had an unexpected encounter with this escapee hiding on an inconspicuous section of the stream bank of Four Mile Run near Bon Air Park last fall. I had just come home from the Falls Church Farmers Market on a Saturday morning in late November and was about to enjoy a piece of warm spinach quiche and a cup of coffee when I got a text from my neighbor and fellow ARMN member, Mikki Atsatt, saying that she had spotted Chinese fountain grass, with its seed heads ready to fling themselves into the water and onto the wind, and said she was on her way to the park to do something about them. Mikki had contacted ARMN president, Phil Klingelhofer, and asked permission to go to Bon Air Park and deadhead these mischief makers ASAP. Not only did Phil approve, he grabbed his collecting pail, and joined in. More later on why she needed to ask permission to remove the seed heads in the park, and why anyone should do this before removing any plant material from a park or natural area.
I ate my quiche and drank my coffee faster than I intended and joined Mikki and Phil at the crime scene where the escapees were hiding. One personal “benefit” of my delay was that by the time I showed up, Mikki had figured out that the seed heads were so ripe that they could be easily stripped by hand, as opposed to having to be cut off. This was a great time saver. Nevertheless, it took about two hours to strip the seeds off that stand of fountain grass. Ninety nine percent of them went into our buckets to be emptied into the trash for disposal; however, it was impossible to prevent a few seeds from dropping onto the ground or getting stuck to our clothing. Ugh!
While the seed heads look soft and fluffy to the eye, according to the Vascular Plants of North Carolina website, the seeds are “notorious for their extremely strong and sharp spines which catch on clothing, fur, and skin alike.” Indeed, my clothing was covered with them when I left, so I can confirm how easily these seeds, which are like a grain and open after a hard freeze, can be spread not only by wind and water but by animals (including humans). Unfortunately, all we were able to do that Saturday morning was thwart the immediate spread, but every little bit helps.
What if You Already Have This Plant in Your Yard?
If you have Chinese fountain grass in your garden, consider removing it, or at least deadheading it every fall and dispose of the seeds in the trash before they break open. According to Jennifer Soles, Arlington Parks and Recreation’s Natural Resource Specialist, it has been found in numerous natural areas in the County, and once established, it is difficult to dig up. Ms. Soles said that the County is looking at strategies for controlling it in the future, and that she expects Chinese fountain grass to be added to future lists of invasive plants impacting our entire region. Meanwhile, until control methods can be employed, she said, removing the seed heads helps to slow the spread, so volunteer efforts are welcome.
Besides the clumps found in the Bon Air Park area, more was located along Four Mile Run in nearby Dominion Hills. In addition, ARMN member and Park Steward, Marion Jordan, reports that she and her team of volunteers have been fighting an infestation at Barcroft Park. Another stand of it was noticed by ARMN member Colt Gregory at Potomac Overlook Regional Park near the Visitor’s Center last summer. He and fellow ARMN members Linda Willen and Marion Jordan got permission from the park manager to deadhead it. Since then, volunteers have been digging the plants up, and plans are being made to replace them with native plants.
While you as a concerned citizen might want to grab the nearest pruners or shovels and attack this grass when you see it on public property, such as parks and stream sides, please resist the urge to do so on your own. The sites I discussed above are being worked by trained volunteers who have permission from local park authorities to do so. It isn’t that your enthusiasm wouldn’t be appreciated, but invasives-removal must be done by people who have had approved training on how to distinguish a true invasive from a native look-alike and on avoiding collateral damage to nearby vegetation or soils. If you see something you suspect is Cenchrus purpurascens growing in a park or other natural area, you should contact the park authority for the county or city where you found it to report the location so they’re aware of it in planning future invasives treatments. Most local jurisdictions prohibit the removal of any plant or animal material from parks or other natural areas without specific authorization.
More specifics about Cenchrus purpurascens
I thought all I had to do was take some photographs and the iNaturalist identification app. would label it for me. It was more complicated than I expected because the plant is known by different names, including even more than one Latin binomial name! It comes from tropical Asia and Australia and appears in the records both as “Cenchrus purpurascens (Thunb.)” and “Pennisetum alopecuroides (Spreng.).” My first reaction was, “Wait, what the heck are Thunb. and Spreng?” I learned that they were botanists who separately named the plant: Carl Peter Thunberg, a Swede who studied under Carl Linnaeus in late 1700s, and Kurt Polycarp Joachim Sprengel, a German botanist working around the same time.
I then decided to search the Digital Atlas of the Virginia Flora, which identifies it under Cenchrus purpurascens and notes that “Molecular studies indicate that Cenchrus and Pennisetum form a monophyletic clade [meaning they had a common ancestor] and should be merged. Nomenclaturally, Cenchrus has priority over Pennisetum.” In addition, as noted above, the Plant Invaders field guide refers to it as Cenchrus purpurascens. It felt like a major victory to finally know the name of what to write about! (However, as explained above, be aware that you will also encounter it as a pennisetum.)
Cenchrus purpurascens is also called various common names in the trade, including Chinese fountain grass, Chinese pennisetum, and swamp foxtail fountain grass. In addition, there are several cultivars of this plant sold in the landscape trade. (There is also a related grass called African fountain grass or Crimson fountain grass (Cenchrus setaceus). This fountain grass is more of a problem in Western states, however.) By any name or any origin, avoid purchasing and planting any of these Cenchrus grasses. If you already own one, consider digging it up and replacing with a native alternative (discussed below), or cut off the seed stalks and put them in the trash at the end of the season before they spread. Please do not compost them or place them your organic yard waste bin. The seeds will germinate and keep spreading in the yards of people who use municipal compost in their own gardens.
What Should You Plant Instead of a Non-Native Ornamental Grass?
If you want attractive ornamental grasses in your garden, there are locally native alternatives to Cenchrus purpurascens, such as river oats (Chasmanthium latifolium), purple love grass (Eragrostis spectabilis), pink muhly (Muhlenbergia capillaris), switchgrass (Panicum virgatum), and Indian grass (Sorghastrum nutans). These are all generally native to Northern Virginia, but it’s always best, check the Digital Atlas of Virginia Flora to be sure a plant is locally native to your particular location.
While I will not go into it here, there are other introduced ornamental grasses such as Chinese silver grass (Miscanthus sinensis), which also seed themselves into natural areas and are becoming invasive. There are native alternatives to these as well. Take a look around your garden and see if you find some introduced grasses that you can replace with locally native alternatives. If that involves more work than you are up for, at least cut the seed heads off before they ripen and escape. You would be surprised how far away they can spread to our meadows, woods, and streams.