Wednesday, September 21, 2022

Stilt Grass: Discovery

I write a lot about dealing with Japanese stiltgrass, Microstegium vimineum.  I do really feel like I am making progress, but the  work is very tedious and the rewards are often delayed.  One way that I've been getting more immediate gratification is to watch for new plants discovered under the (hopefully decreasing) cover of stiltgrass.  Sometimes I'm finding new plants, but also finding increasing numbers of desirable species is a huge boost.  

Two new species for me this year are downy agrimony, Agrimonia pubescens, and whitegrass, Leersia virginica.  The agrimony was growing on the shady edge of a woodland that had been treated with a preemergent herbicide for a couple of years followed by some maintenance pulling of the stiltgrass.  The wands of bright yellow flowers made me think of a short goldenrod, but seeing the distinctly divided leaves led me to focus on some species of Agrimony. The form and small size of the seed pods, shape of the stipule and the hairiness of the stem confirmed the identity as downy agrimony, Agrimonia pubescens.  I hope to see more of this in the coming years. (I will skip using the preemergent in this area next spring.)  I found the Minnesota Wildflowers site to be very useful in identifying this species.  What was very useful was that it had photos of the same plant parts for each species.   

Downy agrimony blooming in August
at the edge of the woods.

Agrimony can be spotted by their distinctive divided leaves and
sharply toothed leaflets.  If I had just seen the three terminal leaflets,
I would have thought of some weedy potentillas, like mock strawberry.

The stipules of downy agrimony are a key feature of the
species, sharply lobed and distinctly divided.

The whitegrass almost got pulled, as on first seeing it I thought it was a tall mass of stiltgrass growing in the middle of the woodland.  As I got closer I could see that the leaves lacked the silvery mid-rib of stiltgrass and the leaves were narrower.  Also the flowers were small and white, not the buff color that I typically see with stiltgrass.  While I did not key out this grass I am pretty sure that it is actually whitegrass and a welcome addition to the woods.  If this catches hold though I will need to be more careful not to pull it as I am ripping out handfuls of stiltgrass growing nearby. 

The white flowers of whitegrass are pointed out here. 
Also note the long slender leaves.  This perennial grass
 is more strongly rooted than the annual Japanese stiltgrass. 

Here I'm holding some stiltgrass (Microstegium)
 next to the native whitegrass.  Note the broader
leaves and silvery center vein of the stiltgrass.

Some other plants that I am seeing more of this year include the native annual sweet everlasting, Pseudognaphalium obtusifolium, growing on a sunny edge of a mown pathway, more and larger masses of panicled tick-trefoil, Desmodium paniculatum, and more instances of what I believe are wood ferns, probably Dryopteris intermedia.

Panicled tick-trefoil tends to grow well in the midst
of meadow grasses.  This puts if at risk of being pulled out
when going after stiltgrass.  It is saved by its plentiful
purple flowers. Shown in the inset are its trifoliate leaves

I think this is intermediate woodfern, Dryopteris intermedia
I usually like to see what the sori look like to do an ID,
but this plant didn't have any. In general I'm seeing an increase
in ferns, this may be as much due to cutting back the wineberry
in the spring reducing as it is pulling out the stiltgrass.

Of course not every new thing is good.  I also found my first instance of wavyleaf basketgrass, Oplishmenus undulatifolius.  While I was not happy to see this, it good that I did and could rip it out immediately before this very invasive grass could get a foothold.  According to the SEEK app sightings of this grass are uncommon this far west in Maryland.  To report this I downloaded the MAEDN app, an app for reporting sightings of invasive species in the Mid-Atlantic region.  This app can be used for all types of invasive species including the spotted lantern fly.

At first I though that this looked like a variant of deer
tongue grass, with crinkled leaves, but on a second
look the way that the leaves were attached and the growth habit
were very different.  The 'SEEK' app quickly ID'ed this as
wavyleaf basketgrass, a recent and very serious invasive species
in the Mid-Atlantic region.

Patrolling the woods for stiltgrass also is an opportunity to identify and remove seedlings of other invasives that were hidden under the stiltgrass like burning bush, bush honeysuckle, barberry and autumn olive.

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