Miscanthus sinensis (Anderss.) is a perennial grass species being considered for bioenergy production in the United States. With its ability to set viable seed and tolerate a wide range of adverse conditions, this species offers practical advantages over current cultivars of the higher-yielding sterile hybrid species Miscanthus x. giganteus. Yet these very attributes may predispose M. sinensis to escape and establishment outside of cultivation. Indeed, several state and regional invasive plant councils currently list M. sinensis as a threat to natural areas. However, very little work has been done to characterize extant M. sinensis populations in the United States. As part of a larger project comparing M. sinensis in its native and introduced ranges, we sampled six populations in natural areas in the eastern United States in summer 2009. We measured the spatial extent and density of each population and derived spread rates from historical records of initial introduction events, in order to provide a first estimate of M. sinensis invasiveness in natural areas.
The Miscanthus sinensis populations we sampled were located in Ohio, Kentucky, Pennsylvania, New Jersey, and North Carolina. They ranged from 0.6 (KY) to 3 (NC) ha in area, and densities ranged from 1,650 (NJ1) to over 15,000 (KY) individuals/ha. Historical records from several of these populations show that M. sinensis is capable of spreading from 5.2 (NC) to 61 (NJ2) m/y. Furthermore, a dispersal study currently underway indicates that seeds of Miscanthus species can travel at least 400 m from a seed source. In an effort to standardize the definition of “invasive”, Richardson et al (2000) suggest that invasion occurs when a fertile species establishes new populations over 100 m from an introduction site within 50 years (2m/y). Our data support the use of the term “invasive” for the M. sinensis populations we sampled. Further investigations should be carried out to characterize weedy genotypes and to identify habitats at particular risk of invasion, but, in the meantime, we urge the bioenergy industry to employ the precautionary principle in further development of M. sinensis cultivars.