Thursday, July 23, 2020

Oplismenus undulatifolius at Patapsco Valley State Park (Avalon Area)

Oplismenus undulatifolous

The new invader was first discovered in 1996 in Patapsco State Park in Maryland (Peterson et al, 1999). 15 years later, it had spread to thousand of acres in Maryland, Virginia, and even one spot in Pennsylvania. But its origin in the USA was at this park, and on the way home from Shenandoah we visited it for a very short while to see first hand its presence in the park.

We entered the Cascade Falls Trail using the Cascade Trail North Carpark, and a short walk of around 15 min quickly took us to one of the falls. At the falls itself I was interested in seeing a single plant growing from between two smooth rocks in front of the waterfall, and nearby was a young colony at the base of a tree.

Oplismenus undulatifolous
A single specimen peeking out from rocks near the waterfall
On the trail itself I encountered a few colonies of the species, and what was interesting was that quite a few of the specimens in the area had leaf damage. Although at first I thought this was from too much light or from some herbicide, Dr. Vanessa Beauchamp said that it was most likely leafminers that caused it. Indeed, it seems a few insects like the leafhopper Tylozygus geometricus and wood midges (Lestremiinae spp) can also cause damage.

Oplismenus undulatifolous
Damage from leaf miners
The damaged grasses though were confined to one area of the trail, and many of the other specimens that I saw were fine.

Oplismenus undulatifolius
Clumps of O. undulatifolius along Cascade Falls Trail, with some of the individuals showing leaf damage.
I was also surprised to discover masses of the species intermixed with other weeds on the slopes of the trail area which can be viewed only from across from the parking lot. I had to use my telephoto lens to get close enough to identity the grass.

Oplismenus undulatifolous
Masses of O. undulatifolius on the side of a small hill, I used a telephoto lens to view it.
All in all I enjoyed the very short stop at Patapsco Valley State Park, and wished I had more time to explore more of the area. Perhaps one day when we pass by again.

Literature Cited

Peterson, P.M., E.E. Terrell, E.C. Uebel, C.A. Davis, H. Scholz, and R.J. Soreng. 1999. (Scientific Note) Oplismenus hirtellus subspecies undulatifolius, A new record for North America. Castanea 64:201-202.

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