August, peak season for .... Stilt Grass 😒

As August settles in many of the landscape chores are on standby.  It's too hot and or dry to plant and mostly too late for pruning.  But it is prime season for pulling out Japanese stilt grass, Microstegium vimineum, and other invasive species before they start flowering and going to seed.  

Here's a shady hill side where I am pulling Japanese stilt grass. 
The right hand side is 'complete', but haven't started on the left. 
This is my third year of trying to manage this area.  There may
be fewer individual stilt grass plants, but they still cover the area.  

Actually I have been pulling up stilt grass as time allows since early July, but around here, August is when it puts on its growth spurt before starting to bloom.  Pulling is most effective when the ground is a little moist and this shallow rooted plant comes up easily.  Unfortunately it has been quite dry here again this year and the stilt grass stems are becoming brittle.  So rather than pulling up the entire plant, it breaks off leaving rooted portions close to the ground.  As I have written in earlier posts, stilt grass has flowers hidden in its stem (cleistogamous flowers) that will develop even if the upper parts of the plant are removed.  A single stilt grass plant forms roots at multiple nodes that are close to the soil, often extending 1-2 feet from its origin.

It is important to do one area really well, rather than pulling a little bit over a larger area.  By removing all of the offending plants in a small area, that area has the potential of becoming invasive free, requiring less attention in future years. (One still needs to monitor a cleared area to prevent reinfestation.)  If you only remove a portion of the invasive species it will continue producing a new crop of seeds and continuing the infestation.  In areas that used to take me over an hour to clear, I now only need about 20 minutes to clean up.

While pulling stilt grass is tedious it gives you the opportunity to get close to plants to identify what else is present.  This can reveal other plants you didn't know you had.  You can also find other undesirable species and get them out before they get established.

One relatively new invasive species to the Mid-Atlantic is wavy leaf basket grass, Oplishmenus hitrellus subsp. undulatifolius.  I have been finding increasing amounts of this each of the past three years.  It can form dense mats that exclude other species.  It bloom in mid summer to mid-fall.  I have left a large trash bag in the woods that I can put these in to minimize the chance to spreading any seed.

Wavy leaf basket grass can be recognized by its pointy leaves and
rippled texture (see arrow).  Like stilt grass it will root all along
the stem, making it a little trickier to remove.  

Another invasive that shows up later in summer is beefsteak plant or shiso, Perilla frutescens.  This exotic annual is originally from Asia where is it used as a culinary herb.  It is a member of the mint family and its leaves have a licorice-mint scent when rubbed.  It can displace native vegetation, particularly in moist locations.  Its leaves are toxic to wildlife, giving it a competitive advantage over native vegetation.

This beefsteak plant seedling could grow to several feet in height. 
It can be distinguished by its large deeply veined leaves and
its minty scent.  Leaves can take on a reddish cast as they age.

Some of the more interesting native species that I have uncovered while clearing out stilt grass include several species of tick trefoils (Desmodium sp.), a witch grass and at least one unfamiliar aster, which I flagged for future ID. Following are some photos of easily missed native species.

Clearweed is native annual usually found in shady, moist locations. 
It is a member of the nettle family, but has no spines.  It can be
recognized by its deeply veined leaves with rounded teeth (crenate)
on its margins.  Dense patches reappear every 2-3 years.

I usually find the showy tick trefoil growing in the midst of taller grasses. 
The egg-shaped leaflets are a clue to its ID.  In late summer
it blooms with panicles of 1/2 inch lavender-pink pea-like flowers.
[This may be a different species, possibly velvety tick-trefoil, D. viridiflorum]

Wild basil usually appears on the edges of taller grasses. 
The leaves are deeply veined and have a grayish
cast due to fine hairs.  The pinkish flowers are in dense heads
or in clusters on the upper leaf axils.  Note the silver-veined
 leaves to the lower right are from panicled tick trefoil, not stilt grass.

White grass is sometimes confused with Japanese stilt grass. 
It has a similar shade of green, but its leaves are longer
and lack the silvery midvein of stilt grass. It is found mostly
 in moist, shady locations but can be in drier areas as well.

These 'dead men's fingers' probably Xylaria polymorpha, is a fungus
that grows off of dead or dying wood.   In this case from the roots
of a former ash tree.  I spotted these in early July.

In addition to locating new plants I noticed a variety of insects that were new to me. I have found that the 'Seek' app is very useful in identifying many of the unknown plants and animals that I have encountered.

This 1/2 inch robber fly, Gray Goggle Eye, will perch on taller grasses
 and other plants while searching for prey.  It stayed in place long enough
for me to get a good photo to submit to the Seek app on my phone. 
It feeds on other flying  insects and is also known as a 'small gnat ogre'.

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.