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Wavyleaf Basketgrass Moves in
Waves through Maryland Forests
Have You Seen It?
Attention Citizen Scientists!
Help Control Wavyleaf Basketgrass
If you have seen this NEW and Highly Invasive Species,
Report Your Sightings
 Two small
populations of a Eurasian grass never previously found in the US
were discovered in Patapsco State Park by sharp-eyed botanists in
1996. Smithsonian Institution and international experts confirmed its identity as an
exotic subspecies of a grass that is native to sub-tropical and
tropical regions, including the southeastern coast of the US.
The native grasses are Basketgrass (Oplismenus hirtellus) and its related native
subspecies Bristle Basketgrass (Oplismenus hirtellus ssp.
setarius). The exotic subspecies is Wavyleaf basketgrass (Oplismenus
hirtellus ssp. undulatifolius).
In 2000, a private
consulting ecologist found this grass by a wooded stream on the
property of the Hernwood Landfill in Baltimore County. Last year
this shade-tolerant moist forest grass turned up more than 20 miles
away in Little Paint Branch Park in Prince George’s County, where is
it being actively removed by groups of volunteers. During this dry
summer, this fast-moving grass was one of the few plants obvious on
the forest floor, and now that fall has arrived, it is blooming and
producing seed.
Wavyleaf
basketgrass is a striking grass. It is a low-lying, trailing
perennial grass, branching and rooting at nodes along creeping stems
called stolons. The leaf blades are flat, about ½ to 1" wide and between
1½ and 4” long, deep green with rippling waves across the grass
blades, as though the tide were coming into shore along the leaves.
They have elongated pointed tips. The leaf sheaths and stems are
noticeably hairy, although the hairs are very short. This
characteristic distinguishes it from its closest relative
Oplismenus hirtellus ssp. setarius, which occurs
naturally in the southeastern US and Mexico and has only a few
hairs, if any. When it blooms, from mid-September well into November,
the grass spikelets have glumes (lower bracts) with very long awns
(extended pointed tips). The awns produce a sticky substance that
allows the grass seed to adhere to passing animals and so disperse.
If you walk, run, bicycle, horseback ride or pass through a patch
of this grass right now,
the seeds will stick to your pants, boots and vehicle and can be
moved to new
uninvaded locations
(see photo below). Please take precautions.
 It is unclear how Wavyleaf basketgrass first came to the US and to Maryland, although
it is possible that the Baltimore County landfill was the unwitting
source of the natural area infestation, spreading from hanging
basket plantings that someone threw away. Variegated varieties of
the related O. hirtellus ‘Variegatus’ are sold ornamentally
as “Ribbon grass” or “Basket grass,” but the wavyleaf subspecies
does not seem to be sold in the horticultural trade. It does appear
to spread rapidly through wooded natural areas: the Little Paint
Branch pockets of infestation add up to about 3 acres, and in
sections of Patapsco Valley State Park, the grass covers more than
150 acres.
DNR has begun to
map the extent of the infestation, and is taking steps to limit the
spread of this invasive grass. If you hike, bike, horseback ride,
or simply walk your dog in Maryland forests, especially in moist
forests along waterways, please keep an eye out for this grass. If
you think you have seen it, please let us know where and how much of
it there is (a few plants, patches, groundcover carpets). Digital
pictures, especially close-ups, of the plant are extremely helpful
for identification purposes.
Photographs courtesy of Kerrie Kyde and John Snitzer
(top to botom):
- A spreading invader -- everything on the ground plane is wavyleaf
basketgrass
- Typical growth habit of wavyleaf basketgrass
- Wavyleaf basketgrass foliage
- A group of Oplsimenus flowers (inflorescence) showing the sticky
purplish awns that help distribute the seeds
- A built-in distribution system: a researcher's pant legs are covered with awns and seeds
Wavyleaf basketgrass and another invasive forest grass, Japanese stiltgrass (Microstegium vimineum) inhabit the same forests and look similar. Here are some ways to tell the difference between them.
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Japanese stiltgrass carpets look “pillowy” and
fluffy on the forest floor. |
Wavyleaf basketgrass carpets are
regular and even.
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While Japanese stiltgrass and wavyleaf basketgrass both look a bit like short bamboo, stiltgrass leaves have a silvery stripe of hairs running down the middle, or slightly to one side and end in a blunt gradual point. Wavyleaf basketgrass leaves have ripples across their width and taper quickly to an elongated sharp point.
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Here you can see the two species together,
stiltgrass on the left and
wavyleaf basketgrass on the right. |
Japanese stiltgrass stems(on left)
are smooth; wavyleaf basketgrass
stems have long silky hairs. |
Where the two species grow together, they do not often intermingle. You can almost see the line of separation between wavyleaf basketgrass on the left, and stiltgrass on the right.
Wavyleaf Basketgrass in Maryland:
An Early Detection Rapid Response Program in Progress
Wavyleaf basketgrass is of interest not only because it is
new to North America, but because it creates an Early
Detection -- Rapid Response situation for scientists and
land managers. This poster was presented at the 2008
Northeastern Weed Science Society meeting. You can download
a pdf version at
http://www.dnr.state.md.us/wildlife/download/wlbg_poster011108.pdf
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