Flame grass, scientifically known as Miscanthus sinensis ‘Purpurascens’, is a popular ornamental plant chosen for its visual appeal in gardens. A common concern among those considering this plant, or those who already have it, revolves around whether it poses an invasive threat to local ecosystems.
Understanding Flame Grass
Flame grass is a warm-season ornamental grass that typically grows in an upright, clump-forming habit. Its medium green blades develop a reddish tinge as summer progresses, transforming into a brilliant orange-red or burgundy in the fall. In late summer, reddish-tinged flowers emerge, turning into creamy white, plume-like seed heads by fall. These plumes often persist through winter, providing continued visual interest.
This plant usually reaches 3 to 4 feet tall, with a spread of 2 to 5 feet. It is adaptable to a wide range of soil conditions, from well-drained sand to heavy clays, and prefers full sun for optimal growth. Native to East Asia, Miscanthus sinensis was introduced to the United States in the late 1800s and became widely cultivated for its aesthetic qualities.
Is Flame Grass Invasive?
Yes, in many regions, certain cultivars of Miscanthus sinensis, including ‘Purpurascens’, are considered invasive. Its invasive nature stems from characteristics that allow it to spread aggressively beyond cultivation. A primary factor is its prolific self-seeding; the plant produces viable seeds that are dispersed by wind. Many cultivars, even those marketed as sterile, produce viable seeds; ‘Purpurascens’ is specifically noted for this.
Beyond seed dispersal, flame grass also spreads through short, branching rhizomes, allowing clumps to slowly expand. This grass exhibits rapid growth and adaptability to various environmental conditions, tolerating a wide range of soil pH, heat, and drought once established. These traits enable it to colonize disturbed areas such as roadsides, abandoned fields, and forest edges, where it can quickly outcompete native vegetation. Invasiveness varies by region, with warmer climates often experiencing more aggressive spread. Miscanthus sinensis is currently listed as invasive in at least 25 U.S. states and Ontario.
Impacts of Invasive Flame Grass
Invasive flame grass can have several negative consequences for natural ecosystems. It forms dense bunches that displace native plant species by outcompeting them for sunlight, nutrients, and space. This displacement reduces local biodiversity, as flame grass can establish monocultures, altering plant communities. Such changes also impact wildlife, as these non-native grasses do not provide the same habitat or food sources as native flora.
Furthermore, the substantial amount of dry biomass produced by flame grass presents a heightened wildfire risk, especially in fire-prone areas, intensifying fires and making them more difficult to control. Another concern is the slow decomposition rate of its leaf litter, which hinders the natural return of nutrients to the soil. Controlling large infestations can also incur considerable economic costs.
Managing Flame Grass and Alternatives
Managing existing flame grass populations requires consistent effort to prevent its spread. For individual plants or small areas, manual removal by digging out the entire root system is an effective method. Dispose of the plant material properly, for instance, by solarizing it in thick black garbage bags before discarding to prevent further spread. To limit seed dispersal, gardeners should remove the plant’s seed heads in the fall before they mature.
For larger areas, repeated mowing throughout the growing season can control or eliminate flame grass, often within two seasons. Chemical control, using systemic herbicides like glyphosate, can be applied to actively growing foliage, particularly after cutting back old growth to encourage new shoots. Burning is generally not recommended as a standalone control method, as it can stimulate growth and increase seed production unless immediately followed by chemical treatment.
For non-invasive alternatives with similar aesthetic qualities, gardeners have several excellent options. Native grasses such as switchgrass (Panicum virgatum), big bluestem (Andropogon gerardi), little bluestem (Schizachyrium scoparium), and prairie dropseed (Sporobolus heterolepsis) provide beautiful fall color and plumes without posing an invasive threat. Some newer, sterile Miscanthus cultivars are also being developed, offering a safer choice for those who desire its specific appearance, though availability may vary.