Saturday, July 27, 2019

Elegant Invader: The Spread of Japanese Stilt Grass (Microstegium vimineum)

Japanese Stilt Grass (Microstegium vimineum)

During one particular hike in Hacklebarney State Park, in Long Valley NJ, I noticed a low growing grass that spread in a dense mat along the sides of the trail.

The trail was in a shaded forested area, and so I was somewhat surprised to see the grass flourishing in such an environment.

When I knelt down and examined it, I noticed that the grass that comprised this surprising monoculture had relatively tiny elegant leaves and reminded me of small bamboo.

Japanese Stilt Grass (Microstegium vimineum)
The elegant leaves of Microstegium vimineum
During the next hike at Chimney Rock State Park, in Bridgewater NJ, I made sure to bring my SLR camera and decided to take pics of this grass.

The species, Microstegium vimineum, was just as prevalent in this park, and I was amazed at the way it formed dense mats even in relatively shaded locations.

Japanese Stilt Grass (Microstegium vimineum)
Japanese stilt grass normally forms dense mats along trail edges
The species has a propensity to form dense monocultures along the sides of trails, so hikers seem to be passing through a living carpet on either side.

It was also fairly easy to recognize the grass. Each leaf had a whitish strip running vertically along its dorsal surface, and a close look at the collar region showed ciliated hair growing in profusion.

Japanese Stilt Grass (Microstegium vimineum)
Close-up of leaves and stem
But no matter how elegant or beautiful the grass might be, it is an invasive, and one that is particularly aggressive against native plants.

It was accidentally introduced into the USA in packing material from East Asia in the early 1900s, and it has now spread throughout the entire Eastern part of the country.

Japanese Stilt Grass (Microstegium vimineum)
Around a tree
Microstegium vimineum is extremely competitive against other grasses, especially in low light conditions (Leicht et al, 2005). It also hinders tree seedling growth (Marshall et al, 2009), and is even dominant over other invasive plants (Morrison et al, 2007).

Japanese Stilt Grass (Microstegium vimineum)
Habit of Japanese Stilt Grass (Microstegium vimineum)
One interesting thing about the invasion is that the species seems to spread fairly slowly when left untouched, which indicates that its recent fast spread may have been due to accidental human transport (Rauschert et al, 2010).

Carpet along sides at Hartshorne Woods Park, NJ


Leicht, Stacey A.; Silander, John A., Jr.; Greenwood, Kate. 2005. Assessing the competitive ability of Japanese stilt grass, Microstegium vimineum. (Trin.) A. Camus. Journal of the Torrey Botanical Society. 132(4): 573-580.

Marshall JM, Buckley DS, Franklin JA (2009) Competitive interaction between Microstegium vimineum and first-year seedlings of three central hardwoods. The Journal of the Torrey Botanical Society 136: 342–349.

Morrison, J.A., Lubchansky, H.A., Mauck, K.E., McCartney, K., and B. Dunn. 2007. Ecological comparison of two co-invasive species in eastern deciduous forests: Alliaria petiolata and Microstegium vimineum. Journal of the Torrey Botanical Society 134(1):1-17.

Rauschert ESJ; Mortensen DA; Bjørnstad ON; Nord AN; Peskin N, 2010. Slow spread of the aggressive invader, Microstegium vimineum (Japanese stiltgrass). Biological Invasions, 12(3):563-579.

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