Identify this weed please

Asked June 16, 2013, 4:04 PM EDT

Can anyone please identify this weed, and how to get rid of it? I've tried crab grass preventer unsuccessfully. Elby Davis, Northampton Twp

Bucks County Pennsylvania weed issues

2 Responses

Always difficult to identify from a single photo but based on the picture and your comments you are most likely looking at mary's grass (also known as stilt grass). It is very difficult to control. Here is a link to assist you in comparing what you are seeing to other common weeds and grasses.

Below is a quick tip sheet from Penn State on control of stilt grass.

Vegetation Management
Department of Horticulture
College of Agricultural Sciences
Invasive Plant Species Management
Japanese stiltgrass (Microstegium vimineum)
• Refer to the DCNR Invasive Exotic Plant Tutorial
stiltgrass page
• Herbaceous, annual, warm-season grass.
• Tolerant of full sun to heavy shade.
• Has a sprawling growth habit, with a canopy
height between 12 and 24 inches.
• Seedheads emerge late-August to early-
• Infestations commonly start along road or trail
edges, then spread outward.
Management Keys
As a plant, stiltgrass is not hard to suppress.
However, treatment often begins after stiltgrass has
spread extensively and established a persistent
seedbank, making control difficult.
Target the Seedbank
To eliminate stiltgrass, you have to prevent seed
production, and exhaust the seed lying in wait in the
soil. You should plan on at least a five-year process.
Prevention is Easier
If stiltgrass is just getting onto your site, determine
where it’s coming from. Shale and gravel for roadwork
are common sources. Roadwork where stiltgrass is
already established spreads it even further.
Mechanical Control
Small infestations of stiltgrass are readily pulled. A
trimmer can be effective later in the season (Figure 1),
if you cut the stiltgrass off at ground level. A
lawnmower cuts too high and will not work, as stiltgrass
is a common weed in turf.
Early Control
It is common to first observe stiltgrass along roads
or trails. The infestation tends spread along the road or
trail, then spread away into the understory. It is
relatively easy to treat stiltgrass while it occurs as a
narrow, linear infestation.
Recommended Herbicides
Stiltgrass is susceptible to a number of herbicides,
allowing you to tailor a program that fits your schedule
and the plant community you are trying to preserve.
Preemergence herbicides that are effective against
stiltgrass include pendimethalin (‘Pendulum’), imazapic
(‘Panoramic’), and sulfometuron (‘Oust XP’).
Imazapic and sulfometuron can also be applied
postemergence for effective control of stiltgrass.
Pendimethalin will have the least effect on non-target
species of these three materials, but it is also the least
flexible to use. Pendimethalin must already be in the
soil where the seed is germinating – it has to be
absorbed by the emerging root tip to be effective.
Pendimethalin has no effect on already established
Imazapic and sulfometuron provide more flexibility
in terms of application timing, but they will cause more
injury to non-target herbaceous plants than
Three postemergence herbicides that are effective
against stiltgrass include glyphosate (‘Aquaneat’),
glufosinate (‘Finale’), and quizalofop (‘Assure II’).
Glyphosate is non-selective and systemic, and will
injure all treated vegetation. Glufosinate is also nonselective,
but it is a ‘contact’ herbicide, so the damage
to treated non-target plants will be limited to where the
spray contacted the plant.
The herbicide quizalofop only injures grasses.
Stiltgrass is affected by quizalofop at low rates, so you
can control stiltgrass but leave native woodland
grasses such as whitegrass (Leersia virginica),
nimblewill (Muhlenbergia schreberi), and autumn
bentgrass (Agrostis perennans) largely intact.
Alternate Groundcover
If conditions permit, you should try to establish a
groundcover to compete with the stiltgrass. If there
already is groundcover, try to encourage its growth.
Turf that is mowed too short and too often is more
prone to stiltgrass infestation than a properly
maintained turf.
Be Persistent
Stiltgrass can only be effectively controlled with
repeated, annual effort. If you back off one season, the
seedbank will be replenished, and your progress to
date will be set back.
This work was sponsored by the Pennsylvania Department of Conservation and Natural Resources, Bureau of State Parks (PA DCNR).
By Art Gover, Jon Johnson, Kirsty Lloyd, and Jim Sellmer, 2008. The contents of this work reflect the views of the authors who are responsible for
the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the PA DCNR or The
Pennsylvania State University at the time of publication.
Where trade names appear, no discrimination is intended, and no endorsement by the Penn State College of Agricultural Sciences is implied.
Table 1. Prescriptions for elimination of Japanese stiltgrass focus on preventing seed set. Stiltgrass is susceptible to a number of
herbicides suitable for use in parks. Small infestations can be pulled or cut at ground level, which facilitates the use of volunteers.
timing treatment product rate comments
early- to mid-
March ‘Pendulum Aquacap’ 4.2 qts/acre
Preemergence applications of ‘Pendulum’ (pendimethalin) prevent stiltgrass
establishment, and have little effect on plants that are already present. It is
critical that pendimethalin be applied two to three weeks prior to germination
to allow rainfall to move it into the soil profile. Pendimethalin is also effective
against mile-a-minute.
through May
‘Oust XP’
8 to 12 oz/acre
1 to 3 oz/acre
‘Panoramic’ (imazapic) and ‘Oust XP’ (sulfometuron) have pre- and
postemergence activity against stiltgrass. Preemergence applications will
cause less damage to non-target species than postemergence applications.
There comes a point in the season when you are better off using an herbicide
that is not soil active (see below), to reduce the impact on non-target plants.
‘Assure II’
24 oz/acre
4 qts/acre
4 oz/acre
‘Aquaneat’ (glyphosate) and ‘Finale’ (glufosinate) are non-selective
herbicides with no soil activity. ‘Finale’ only injures the parts of the plant it
contacts, while ‘Aquaneat’ is systemic, and will kill the entire plant. ‘Assure II’
(quizalofop) only affects grasses, but the rate used for stiltgrass is low
enough that desirable grasses such as whitegrass (Leersia virginica), and
nimblewill (Muhlenergia schreberi) are only temporarily affected.
July through
August pulling or cutting n/a
Small infestations of stiltgrass can be mechanically controlled. If you’re
cutting, use a trimmer that will cut the stiltgrass at the ground line to prevent
resprouting from the lower nodes of the stem. The key to this treatment is to
wait so that more stiltgrass will not germinate, but finish before the
seedheads emerge.
This publication is available in alternative media on request.
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harassment against any person because of age, ancestry, color, disability or handicap, national origin, race, religious creed, sex, sexual orientation, gender identity, or
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nondiscrimination policy to the Affirmative Action Director, The Pennsylvania State University, 328 Boucke Building, University Park, PA 16802-5901; Tel 814-865-4700/V,
Figure 1. The objective of stiltgrass management is to prevent seed set. Stiltgrass is effectively controlled with
preemergence or postemergence herbicide applications, and small infestations can be hand-pulled or cut at ground level.
germination flowering and seed ripening
‘Pendulum’ herbicide
‘Oust’, ‘Panoramic’ herbicides
‘Aquaneat’, ‘Finale’, ‘Assure II’ herbicides
pulling, cutting

I think that is it. It seems to prefer the shady areas of my property. Thank you.