PA Youghiogheny Floodplain Scours

There is no better time to visit the Youghiogheny River than in early fall when water levels are lower, giving access to the scour zones of the river's hard-washed edges. These are banks or ledges of stone that for the most part are underwater during the rest of the growing season, but come early autumn they become great places to botanize. It takes a tough group of plants to call the scours home.

Most rocky rivers have some version of a scour zone, especially if winter ice plays a factor in scrubbing these fragile habitats clean just ice-out and spring floods begin. The Susquehanna has its most famous scour banks close to where I live. I am always in awe of the persistence and beauty of plant life that erupts there at the end of each summer.  Exploring such a place puts you literally on the edge of where life is possible. Add to that, scours are relatively rare in Pennsylvania. When I saw the rocky ledges along the Youghiogheny full of prairie grasses and wildflowers I knew I had to get down there to have a look around. 

Late-season Boneset, Blue Flag Iris, Goldenrod, and a heathy stand of native Switchgrass greeted me as I waded into the waist-high meadow that for most of the year is underwater or ice. St. John's-Wort a stand of low-growing Silky Dogwood seemed to go hand-in-hand, where there was one, there was the other. Cockle Burr and Cardinal Flower added a contrast of growing types, from low-to-the-ground then spiking high above the competition. For all the variety of plants found on this long, low bench of exposed sandstone exhibited every growing strategy for this here-and-gone-again meadow.  

Silky Dogwood

At the edges of the scour zone, where flooding is more frequent, little else grows on the hard rocky bank. High waters have scrubbed the flats clean of any soil pockets. But nearby, where a skim of soil survives, a riot of plants occupied the edges. Steeple Bush and Silky Willow held the soil flats in place while all manner of neighbors filled in. It was hard not to find a square meter of thin soil that didn't have a dozen or more species growing in it! 

Scour stripped to bedrock

As I expected there was significant competition with a raft of non-native species. Japanese Knotweed threatened to take over an entire section of scour ledge while a healthy, and prickly, stand of Common Teasel scraped at my legs and arms. A few garden-variety Hosta lined the faint outline of a trail - as did a scattering of summer's trash left over from river visitors. 

Early Goldenrod 

Soon the first frosts will take their toll on the flowering plants leaving the Rushes in all their glory. Spiked Rush, Canada Rush, Sharp-Fruited Rush, and Creeping Spike Rush were waiting for their moment to overtake the scour land. The Purple Top grass was in full color and set against the yellow of Goldenrod, put on quite a show. 

Common Teasel

"Bearded" leaf node of Purple Top grass

My favorite find is the bearded leaf node of the Purple Top grass, where the leaf sheaf unfurls along the stem and reveals a bristly, pink patch of hairs. This is an easy way to identify this native grass but also one of my favorite ways to entice students to look closer and any native grass stand for this singular and sometimes dramatic (who wouldn't love a pink beard?) identifiers. 

On my out of the floodplain scour zone I met up with a family coming in. They were trying to access the river for a less-crowded experience compared to what they encountered just downstream. "This is beautiful!" their mom exclaimed, so I took the opportunity to explain what made this area so very special. "Well," said their dad, "We will leave this place alone and not wade here - but let's visit with the flowers before we go."

Notes:

Youghiogheny River Scour - Western Pennsylvania Conservancy