Wednesday, August 22, 2018

The Changing Flora Along the Kayaderosseras Creek (2018)

There's a trail along the Kayaderosseras Creek near Ballston Spa that is serving as quite a laboratory regarding the succession of plants after a site has been denuded.  The photo above was taken this week, with abundant shrubs and herbaceous flowers teeming along the shore.  The photo below was taken in late December of 2012, after the state's Department of Transportation had reconfigured the creek's formerly steep banks,  beveling them back in order to allow flood waters to flow out over a floodplain instead of charging full-force through a narrow channel and undermining a roadway further downstream. In the process, the DOT removed all the resident trees, shrubs, and herbaceous plants, replacing them with comparable native species. (In the photo below, twigs of Red Osier Dogwood have been layered along the banks.)

This next photo, taken about two years later, demonstrates how the strategy succeeded, allowing a flooding creek to wash out over the beveled banks and onto the floodplain, where a small forest of native trees had begun to take root and grow.

This next photo shows the creek-side plantings less than a year after the banks had been denuded, with a healthy variety of native plants becoming well established by September, 2013. (A few non-natives, too, like that very tall mustard in the foreground, had also found a home here.)

Three years later, in 2016, here's that same creekbank as in the above photo.  Some of the young trees have died, but the herbaceous plants, now well established, have grown to shoulder height.

And here's that same trail today, with many plants towering over our heads and crowding the trail with their branches.

Unfortunately for me, as a wildflower enthusiast, the rich variety of wildflowers I used to find here has been supplanted by a near-monoculture of these tall sunflowers.  I haven't yet figured out which species they are, but I believe that at least they are ones that are native to our area.

Just two years ago, an entirely different species of sunflower, called Maximilian's Sunflower, had emerged as the dominant species along this trail.  Native to more central regions of North America, they had certainly taken a liking to this habitat and climate, with their population exploding from the single unfamiliar plant I had found in 2013, to numbers I feared were becoming invasive by 2016, when the photo below was taken.  As this photo also reveals, however, our native New England Asters appeared to be holding their own against the introduced Maximilian Sunflowers.

But last year, I had to search and search to find even ten Maximilian Sunflowers.  And this year, I found even fewer.  Only after diligent searching did I discover several leaf stalks of this very showy plant.  Perhaps when they come into bloom I will be able to find more.

 Even though I feared they were becoming too numerous here, I do miss their gorgeous blooms.

I also miss the marvelous variety of native wildflowers I used to find here in bounteous numbers, the Blue Vervain, Great Lobelia, Wild Bergamot, Purple Coneflower, and all three colors (purple, pale pink, and deep rose) of New England Aster.  All have been mostly supplanted, it seems, by those tall un-named sunflowers as well as masses of goldenrods.  But who knows what the next succession will be?  This landscape certainly has a habit of species impermanence!

Another remarkable quality about this creekside habitat is how it nurtures plants of gigantic size.  There's a thicket of Jerusalem Artichokes that are already towering over my head, and they're probably not yet done growing.   Same goes for the Giant Ragweed pictured below,  almost as tall as some surrounding trees, with a stem about the girth of a broomstick.  Note, too, the Evening Primroses next to it, which loomed at least two feet over my head (and I'm a tall woman, nearly 5'8").

These Joe Pye Weeds had also achieved a prodigious size.  I  wondered if they might be the related enormous species called Trumpetweed (Eutrochium fistulosum), but the herbaceous growth was so thick here, I felt reluctant to push through to closely examine the plants.

Unfortunately, this site is also home to some of our most robust invasive weeds.  Thankfully, we have some native bullies, too, that help to push back against the intruders.  I was glad to see, as this photo shows, that our native Nettles are crowding out some of the pernicious Wild Chervil so as not to let it take over the shaded banks entirely.

When the Department of Transportation planted numerous small trees along the creekbank six years ago, some invasive species hitched a ride here on the rootballs.  The nastiest of these was Mugwort, and by last year it had spread to a distressing extent.  But wonder of wonders, it met more than its match in our native Tall Goldenrod, and this year the Mugwort is scarcer, engulfed by masses of goldenrod.

I doubt we will ever see the thickets of Japanese Knotweed diminished here, but at least the equally stubborn Pale Jewelweed won't let it have ALL the space. I would estimate there are at least equal numbers of jewelweed plants to those of knotweed.  And aren't they beautiful?

Amazingly, even after nearly a decade of closely monitoring the plants that grow here, once in a while I still find a new one.  Last year, I was surprised to find some Tall Ironweed (Vernonia gigantea) holding its own among the Tall Goldenrods.  I was indeed surprised, not just because I'd not found it here before, but because NO ONE had found this plant here before, according to the New York Flora Atlas, which rates this Ironweed as an Endangered species.  So that was quite a surprise.  And of course, I went looking for it again when I returned there this week.  Well, it was gone from where I found it last year, but then, there it was, across the trail in another location!   Perhaps in time a population might yet be established.

I did push through the surrounding thick plant growth in order to closely examine the Ironweed's florets, wanting to make sure this was the rare Tall Ironweed and not the similar New York Ironweed (Vernonia novaboracensis), a more commonly occurring plant.  Sure enough, the lack of hair-fine threads to its pointed bracts surrounding the florets clinched the suspected ID.

Below are two photos of New York Ironweed for comparison, showing the hair-fine bract tips. These plants were growing in a rain garden at Moreau Lake State Park and were not part of a native wild population.

I also took apart individual flowerheads from both species to count the florets, counting 22 florets for the Tall Ironweed and 38 florets for the New York Ironweed.  According to Newcomb's Wildflower Guide, Tall Ironweed has flowerheads containing 13-30 florets,  New York Ironweed 30-50 florets.

I used to find a single plant of Tall Ironweed  about 10 miles from here at the Wilton Wildlife Preserve before it got mowed down by county road crews, who continued to mow its site every year thereafter, so I expect it is now extirpated from that site.  I hope we can at least hold onto this one specimen of Tall Ironweed here along the banks of the Kayaderosseras Creek.   Considering this site's past history, though, I know I can't count on it.

I sure do wish, though, that some of the New England Asters that used to grow here will someday return, to look as beautiful as they did in this photo from three years ago.


Woody Meristem said...

There is nothing so constant in the natural world as change; these are dynamic ecosystems, especially when humans have disturbed them.

Ron Gamble said...

For your unknown "sunflower", are you confident it's not Heliopsis?

Jacqueline Donnelly said...

Ron Gamble, I have found Heliopsis helianthoides (Oxeye or False Sunflower) at this site, but I always could see the little Y-shaped pistils at the base of each ray flower. I examined several of these "sunflowers" that are dominating this site, and I didn't find any fertile ray flowers. But I am not CONFIDENT about them not being Oxeye. I just don't know.

I certainly agree, Woody Meristem, that Nature changes all the time. There are a number of sites I visit each year or several times a year, and I've learned to expect that I will always be surprised by what I find.

Ron Gamble said...

Hmm - I figured you'd checked for fertile ray flowers. It looked like MAYBE there were a few "stems" arising from leaf axils, and the leaves were triangle-like, and all that made me wonder about Helioposis; so at least it was worth asking. :-)