Wavyleaf Basket Grass, the next thing to deal with

Wavyleaf basket grass, Oplismenus undulatifolius, is a relatively recent invader in the mid-Atlantic region of North America.  It was first detected in Howard County, MD in 1996.  It has since spread into the Shenandoah National Park in Virginia (2005) and further north and west into Pennsylvania and West Virginia.  It is originally native to Southern Europe and Southern Asia.

Being out in the western part of Maryland I had hoped that this would just be an urban area problem. However, 2 years ago I spotted the first occurrence on my property and there have been increasing numbers each year since that time.  This year I noticed it as I was doing a final round of garlic mustard removal as it is now fully going to seed and further removal would just result in spreading seed. 

Here's a patch of wavyleaf basket grass that I found on my
property before pulling it out. It's mixed in with some
other invasive species like Japanese
honeysuckle and multiflora rose.

Since it is not yet well established in the outlying areas, control of its spread may be achieved by quickly removing it when detected.  Spending 10-20 minutes clearing up a small patch will save much more time and effort needed to control a much larger patch a year or two later.

Where it grows

It prefers shady moist sites and will not grow in sunny locations.  The dense growth pattern can shade out other plants giving it a competitive edge over native species, as well as some invasives.  It is often found growing with Japanese stiltgrass.  Unlike stiltgrass, wavyleaf basketgrass is a perennial, sending out new shoots and stolons each season in an ever widening circle.  It is not known how long seeds will remain viable in the soil. Seed germination is from April to June.  For occurrences that are only a couple of years old you can trace the outer leaves back to its origin point.

How it spreads

The seeds have sticky awns and will attach to passing wildlife and other traffic. Occurrences of this invasive grass are more often found along paths used by animals and humans. For this reason one must be very careful when exploring the woods that your shoes, clothing, or pets do not pick up seeds and potentially transfer them to new and distant locations.  This is particularly an in issue in late summer through late fall when the seeds are ripe. Seeds can be removed from clothing by wiping with the sticky side of duct tape.  Much of the spread of this invasive species can be linked to recreational activities.  If you've been in an area with seed bearing plants you should take steps to avoid carrying any seeds with you.  Including scrapping off any mud on site and  collecting and disposing seeds.

How to recognize

The most obvious feature of wavyleaf basket grass is the wavy surface of its broadly lanceolate leaves. Leaves are borne alternately along the stem.  The leaf sheaths are covered with long white hairs.  Plants spread outward by stolons that are weakly rooted at every node that can touch the soil or other receptive surface.  I encountered one plant that was well rooted into the bark of a fallen tree that it was growing over.   Seedlings look like miniature versions of the mature plants.  The small white flowers with long, barbed awls appear along spikes at the ends of upright branches.  Flowering starts in mid- to late-summer, with the seeds ripening in late summer through the fall.

It's similar to deer-tongue grass but grows closer to the ground.  The waviness of the entire leaf surface is very distinctive especially in comparison to the flat leaves of deertongue grass. Deertongue grass grows in sunnier sites, part to full sun.  Further south there is a native basket grass, O. setarius that very similar but has few, if any hairs on the leaf sheaths and its flowers are reddish instead of white.  Currently that species is uncommon North and East of Florida and Alabama.  

Here's what deer-tongue grass looks like.  The color and shape
of the leaf is similar to wavyleaf basket grass,
 but the clasping leaves are not at all wavy.

How to control it

Pulling is effective on small patches.  It took me about 20-30 minutes to clear a 30 sq-ft area.  I had a lightweight basket to carry away the plants.  Before they are in bloom, pulled-up plants can be left in the full sun or hung on a branch to dry out if you don't have a means to carry them safely out of the area.  For larger infestations grass-specific herbicides recommended April through June.  After that non-selective herbicides are recommended (e.g., glyphosate) for large areas.  Details about the use and selection of herbicides can be found in the Penn State link below.

This is the area from the very first image after 10-15 minutes of
careful removal.  You can see that very few other plants were growing
under the shade of the basketgrass. 

Since it is so low-growing it is difficult to spot at a distance.  Rather than specifically hunting for this species, one should keep it on your radar and remove it anytime it is located (except when seeds are present, unless you can bag it up safely).  If you are on public property you report the sighting of this species using the Early Detection and Distribution Mapping System or on the iNaturalist  app.

The following references have more images and details about wavyleaf basketgrass:

Blue Ridge PRISM, Virginia DCR, Maryland DNR, and Penn State Extension.