by Dr. Sarah Treanor Bois, PhD
Director of Research & Education at the Linda Loring Nature Foundation
Ornamental grasses are a popular part of many Nantucket landscape designs. They add movement and provide drama, all while giving a naturalized look to the landscape. However, many of these ornamental grasses are now being seen as weedy, if not invasive on the island—we need to do all we can to prevent spread into our natural areas and value our native grasslands.
One ornamental grass in particular has been causing alarm in the conservation community on Nantucket for the past several years: Chinese Silvergrass or Miscanthus sinensis. While you may not know the name, chances are you know the plant. This tall grass grows in large bunches. The elegant, tall plumes can stand over 10 feet tall when in bloom. It flowers late in the summer and holds onto its seed heads well into the fall through January. The feathery seed heads sway in the breeze along driveways and road edges, often flanking entryways. This beautiful grass, though, likes to move beyond where it was intended.
You can also find the plumes along the sandy road edges or creeping into open space, well away from cultivated yards. The wind-dispersed seeds have no problem travelling beyond where they were planted, dotting the landscape of our island known for its blustery winds. Island ecologists and land managers have become increasingly concerned, as they attempt to manage the tenacious grass and try to keep it from spreading into our valuable sandplain grassland and heathland habitats.
Due to its easy maintenance, fast growth, showy flower and seed heads in late summer and early fall, and tall bunched growth, Chinese silvergrass is popular in landscaping. It is adapted to a wide range of habitats, growing successfully in well-draining and moist soil, partial shade, or sun. The very qualities that make it good in the garden also contribute to its invasive characteristics.
Miscanthus is a genus of grasses native to Eurasia and the Pacific Islands. M. sinensis was first introduced to the US in the 1890s. It was brought to Massachusetts in 1916. We don’t know exactly when it was first on Nantucket, but we know its use was widespread by 1970.
In New England, we primarily have two species which have become naturalized, which means they escape cultivation and have established populations outside of garden beds and cultivated landscapes. In addition to the Chinese Silvergrass, we have Miscanthus sacchariflorus, known as Amur Silvergrass. M. sacchariflorus was noted to be aggressive and was evaluated as an invasive in 2005. The Massachusetts Invasive Plant Advisory Group (MIPAG) considered the evidence (including photo documentation, herbarium specimens, and expert testimonials) and deemed the plant as likely invasive. This means it is a non-native plant with the likelihood of causing ecological harm by spreading aggressively, forming dense monocultures and potentially outcompeting native species, especially in “minimally managed habitats.” With this designation, M. sacchariflorus is now on the Massachusetts Prohibited Plant List, which bans the importation, sale, or trade of plants deemed invasive.
That’s good news for those battling M. sacchariflorus infestations. But what about its close relative? When M. sinensis was first evaluated by MIPAG in 2005, it was deemed to have insufficient evidence, stating: “More data needed for minimally managed habitats.” The State looks to hard data: documented occurrences and dense populations in minimally managed habitats. “Minimally managed habitats” are natural areas like much of our conservation land on Nantucket.
We’ve had nearly two decades to assess and gather more data.
This past September, Dr. Sarah Bois and Jenny Kafas of the Linda Loring Nature Foundation again proposed Miscanthus sinensis for listing to MIPAG. In the nearly 20 years since it was first evaluated by the state, many more populations have been found with the increased use of this plant as an ornamental. The recording of occurrences and data collection methods have also improved, with databased like EDDMapS and iNaturalist. MIPAG will vote in December whether to recommend the species for listing on the state prohibited plant list. Data has been gathered from throughout the invasive range of the species, with detailed attention to Massachusetts records. There is a lot of evidence on the islands of Nantucket and Martha’s Vineyard and, hopefully, the evidence from other parts of the state is enough to consider the plants.
Why do we care so much? M. sinensis can form large clumps along disturbed areas, displacing native vegetation. The grass is also extremely flammable and increases fire risks of invaded areas. Not only does it carry fire, but fire can benefit the plant, causing increased spread. Here on Nantucket, the Invasive Plant Species Committee (IPSC) monitors non-native species across the island. The IPSC has been keeping tabs on Miscanthus and the habitats it invades. Of particular concern are our globally rare habitats: sandplain grasslands and coastal heathlands, where Miscanthus has been shown to invade. M. sinensis is a known invader in the southeastern US. We can learn a lot from our near neighbors as our climate becomes more similar to areas like New Jersey and Long Island, where M. sinensis is already seen as a threat to grassland and pine barren habitats. Our milder winters and maritime climate are believed to have contributed to the beneficial conditions for the species.
On Nantucket there have been continuous management efforts by the Land Bank and the Nantucket Conservation Foundation at several sites since at least 2019. M. sinensis has been a target for manual and chemical treatment by multiple conservation groups. The Nantucket Land Bank has dug, pulled, and treated Miscanthus at several properties. On property owned by the Nantucket Conservation Foundation, Miscanthus hot spots are found throughout the Middle Moors and west to Sanford Farm. Knowing how invasive the plant is in other locations; some have adopted a “zero tolerance” policy for the plant.
At the Linda Loring Nature Foundation (LLNF), a few clumps have found their way onto the grasslands. These clumps have been removed; however, the primary problem is along Eel Point Road, where the LLNF team manually digs up clumps every fall. As a wind-dispersed plant, seeds and seed heads blow over onto the LLNF property from surrounding yards. After years of attacking the new recruits, ecologists on- and off-island want to tackle the root of the problem by having the species listed as an invasive at the state level, prohibiting further plantings.
What happens if M. sinensis makes the state prohibited plant list? Once a plant lands on the list, it is prohibited from sale, transport, and trade in the state. The ban isn’t immediate: there is a slow phasing out, especially for plants in the horticultural trade. And the ban doesn’t cover plants already on the landscape, so the problem will continue for some time before the listing has any effects.
How can you help? First: don’t plant any new Miscanthus plants. If you have them, dig them up or make sure to cut the seed heads in fall before they disperse. As with many of our invasive or non-native plants, more documentation is needed. If you see Miscanthus growing on a roadside or in conservation land, photograph it and upload the photo to a database like iNaturalist or EDDMapS. Not sure of the identification? iNaturalist uses crowdsourcing and experts to verify records and help with identification. Make sure photos have close-ups of the inflorescence, habitat photos, and note, where possible, if it is planted or an escaped plant.
There are great native alternatives to planting Miscanthus that provide beauty without the risk of ecological harm. Native switchgrass (Panicum virgatum), big bluestem (Andropogon gerardii), and Indian grass (Sorghastrum nutans) are tall bunch grasses that combine visual appeal with ecological benefits. If you use landscapers or gardeners, ask for these alternatives. Consumer demand can drive change in the absence of state regulations.
Why bother with Miscanthus? At this point, it’s an ecological problem that can be solved. In invasive species management we use the “early detection, rapid response” approach: it is much easier to control an invasive plant infestation while the population is still small. Right now, we are at a critical juncture with Miscanthus: we know it is invading natural habitats, and, if we act soon, we have a chance to address it before it becomes a much more widespread and expensive concern.
Want to help prevent the spread of non-native invasive plants? Contact Sarah Bois at stbois@llnf.org to become added as a volunteer to the Invasive Plant Species Committee for Nantucket.
