November 17, 1949: 68 years ago today

Now it's a common forest invader in Pennsylvania, but it wasn't always. Collected on November 17, 1949, this specimen was found by Bayard Long in Delaware.  Native to East Asia, Japanese stiltgrass (Microstegium vimineum) was introduced by accident to Knoxville, Tennessee around 1919, used as packing material for porcelain dishes from China.  It has since become a major invasive species, spreading across forests of Eastern North America.  It is commonly found along trails, forest roads, and floodplains.  It has been shown to be facilitated by deer overabundance.  A recent study of unconventional gas well pads (such as “fracking”) in Pennsylvania by Penn State researchers found that recent hydraulic fracturing activities facilitates stiltgrass invasion (Barlow et al., 2017 Journal of Environmental Management).  You can read more on that research here.

Japanese stiltgrass was introduced more recently compared to many other troublesome invaders.  It only became common in western PA in the past few decades.  In fact, to my surprise, there weren't even any specimens in the museum's herbarium from Allegheny County (Pittsburgh area)!   (But there are now).

Specimen pictured below was collected in the native range (Japan, hence its namesake) in 1981.

Images below: Japanese stiltgrass invading a forest understory in Fox Chapel, near Pittsburgh, PA.