Stiltgrass is in bloom - The time to act is now!

The flower heads of Japanese stiltgrass are just opening up.
The weedy plants have just had a growth spurt
bringing some of them to nearly 4' tall.

I am in midst of a multi-year battle to get rid of, or at least control, the Japanese stiltgrass, Microstegium vimineum, on our property.  Last year I came up with a plan to bring this invasive species under control.  The key element is to prevent this annual grass from setting seed.  Eventually (5-7 years) the seed bank will be depleted.  Also I am encouraging the existing native plant population to back fill the gaps to suppress re-invasion.

In late August stiltgrass goes into a growth spurt as the flower heads develop.  It is critical to cut it down or pull it out before seed set begins.  By killing the plant before the seeds can mature, you can dispose of the plants by composting.  Otherwise the plants would need to be segregated (e.g. bagged and sent to landfill) to prevent another generation of seed from spreading.  The taller stiltgrass is easier to find and pull than it is earlier in the season.  You should try to remove the plant close to the ground since it also produces a second hidden (cleistogamous) flower in the lower stem.


The following two photos show a moist shady area just before I removed the stiltgrass.

One year after close cutting stiltgrass in late August (2103) the growth is still rather dense.

After two years of cutting there appears to be more gaps in the stiltgrass converage.

In a couple of areas I was weed whacking and composting in place.  After 2 years of this I am seeing some minor decreases in the density of the stiltgrass coverage.  This year I raked the cut grass off and into a pile.  By removing the dense thatch I am hoping to seed some other species move in.  I have another large area where I will leave the cut grass in place.  We'll see if that makes a difference.

American germander blooms in late July and the seed is still maturing,
so I'd like to keep these standing a little longer.

One of my challenges is to remove the stiltgrass while leaving as much native vegetation in place.  Many of the earlier blooming natives, such as the beebalms (Monarda sp.) and tick trefoils (Desmodium sp.) have already gone to seed.  However, there are a number of later blooming species that I'm trying to preserve by carefully hand-pulling around them.  These include American germander, (Teucrium canadense), Virginia knotweed (Persicaria virginiana), white vervain (Verbena urticifolia), white avens (Geum canadense), and the native annual, clearweed (Pilea pumila).  While not beautiful plants on their own these species do fill the woodland edge with a variety of colors and textures largely obscured by the invasive stilt grass.

Clearweed is a fairly common native annual found in shady moist sites.
Currently in bloom, the flowers are yellow tassels in the leaf axils.

Here I'm halfway done with a section revealing some American germander (center).  To the left is my new grass whip.

I recently got a double edged grass whip which does a great job of ripping stiltgrass out of the ground while leaving single bladed grasses largely intact.

This low-growing sedge was hardly disturbed as the weed whip tore out the stiltgrass.

I am also finding a number of native grass species under and within the stiltgrass.  These include the evergreen, spreading sedge (Carex laciculmis) and deer-tongue grass (Dichanthelium clandestinum).

Mid-summer's Little Blooms

In the middle of summer there are many big blooming native plants like Cone Flowers and Black-eyed Susans.  A next post I will take a look at some of the 'prettier' natives that are in bloom now.  But this post I will show you some of the natives blooming with small pale or white flowers.  Many of these could be considered weeds, but I had not ID'ed many of them before, and, of course as native species they are part of the 'original' ecology of the area.

This Virginia Stickseed is about 2 feet tall.  The horizontal
sprays of seed pods give it a unique texture.

The first plant that literally caught my attention was Virginia Stickseed, Hackelia virginiana.  As I was clearing stilt grass from a planted area several branches from this plant caught hold of my sleeve.  When I pulled back These branches broke off, transferring the sticky burr-like seeds onto my shirt.  Originally about 4 feet tall, parts of this plant fell over due to the weight of seeds.  Rather than noticing the small white flowers, what I see now is a a textural affect from the horizontal branches laden with burrs.

Here you can see the progression from flower to burr.  This bee fly is a pollinator
 for many small flowers.  Its larvae are parasites that feed on other insects.

This plant has a highly branched forms, others
in less disturbed areas grow as a single upright stem.

Nearby was one of my favorite little natives, Indian Tobacco, Lobelia inflata.  It is not really showy.  The blue flowers are not very big and the small flowers are spaced widely on the stalk.  What I think is so cool are the swollen ovaries (hypanthium) that form after the flower fades.  This feature is the reason for the species name, inflata.  This plant is used as an herbal remedy for many ailments, particularly as an emetic, but it is also quite toxic.  I've tried growing these from seed indoors under lights with limited success.  It seems to grow better as a 'weed', than as a cultivated plant.

Here you can see both the pale blue flowers
and the inflated hypanthium.

The coarsely toothed, oppositely arranged leaves
on long petioles are similar to those of nettles.

White Vervain, Verbena urticifolia, has spikes of tiny white flowers.  The plant has a rough appearance with its large, coarsely toothed leaves.  The species name uricifolia refers to it having nettle-like leaves.  This is not a particularly attractive plant, but its flowers are visited by a variety of bees and its seeds are consumed by birds.

Here's a closer view of the flowers of White Vervain.  It seems like the tips of the flower stalks are the place for small insects to hang out.

The current botanical name for this
Horseweed is Conyza canadensis.

When I looked past the white Vervain I saw what thought was more of the same, but on second glance I realized that I had yet another plants with little white flowers.  I keyed this one out as Horseweed, Erigeron canadensis, which has been updated as Conyza canadensis. On examination its form is very different from the verbena, with narrow leaves occurring alternately along the stem.  The main similarity was that the flower stalks originated from the leaf axils.  Similar to members of the genus Erigeron, its flower is composite type with many small rays.  This annual is commonly seen in waste areas and fence rows.

A green sweat bee visiting a Horseweed flower.

My last plant for this post was discovered with its flower stalk sticking out of some berry vines in a woodland edge habitat.  Normally I leave a plant in place until I know what it is, but this one had me worried.  It had characteristics of Polygonum (Knotweed) and with its white flowers I immediately thought of Japanese Knotweed.  When I brought the cutting in for examination I learned that it was actually a native knotweed, Polygonum virginianum, aka Jumpseed or Virginia Knotweed.  It is also known and sold as Persicaria virginiana and Tovara virginiana.  This particular specimen had dark green leaves; however many plants have a red chevron on otherwise green leaves.  

This stem got beat up a bit after I pulled it out from a mass of wineberries.
I would have left it alone had I known what it was.

Of these five natives, I think Jumpseed is the most easily adapted to a landscaped garden.  In addition to the red striped leaves and more compact habit, the long flower stalks (up to 3 ft) turn from pale yellow to red as they age.   A cultivar with particularly strong red markings is called 'Lance Corporal'.  Another cultivar called 'Painters Palette' has multicolored leaves.  The biggest negative is that it can reseed vigorously.  Jumpseed does well in dry shade.  I had a client in the Boston area with a large patch of these growing on the north side of the garage in full shade.   I will keep an eye out for more of these so that I can see how the red color develops on the flower stalk.