[MAIPC] Fwd: [NativePlantseast] Smartweed management?

Hughes, Jake jake_hughes at nps.gov
Mon Jul 13 18:32:16 PDT 2015


Lori,

We have a pretty bad problem with Oriental lady's thumb (Polygonum
cespitosum, Persicaria longiseta) here at Shenandoah National Park.  Like
the native PA smartweed, it has pink flowers/fruit, but they're smaller,
and the leaf sheath around the stem (ocrea) is fringed with long hairs.
It's our second most widespread and abundant nonnative weed, and is often
found in near monocultures.  Oriental lady's thumb seems to really thrive
and persist in mesic, higher elevation sites in the park.  At lower
elevations it seems a bit more ephemeral.

Assuming your smartweed is confirmed as this or another of the small
handful of nonnative species, you're correct--you won't find much guidance
on dealing with it.  We've found it's easy to kill, but not very easy to
kill without collateral damage.  A glyphosate product such as Rodeo (54%
glyphosate) can be used at low concentrations (0.5% has been pretty
consistently effective, 0.25% less so) on heavy infestations.  Weed
whacking it close to the ground before seed set can knock it back.  In
upland areas, preemergent products (e.g. pendimethalin, prodiamine) can be
useful, and are probably your best option for avoiding damage to native
perennials.  But these may not be an option if you're near a stream.
Contact herbicides such as pelargonic acid (e.g. Scythe at 5 to 10%
concentration) are also pretty effective, if applied early and before rigid
stems develop.  Flaming with a propane torch should work too, if you're
into that.

Since mowing probably leaves enough above-ground tissue for the plants to
rebound, I doubt it would effectively control Oriental lady's thumb.  And
certainly if it's being mowed after seed set, the seeds are being thrown
far and wide.

Hope this is somewhat helpful, should you need to deal with this plant.


On Mon, Jul 13, 2015 at 6:13 PM, Lori Bowes <lrbowes2 at yahoo.com> wrote:

> Hi.  I get confused about smartweed/knotweed but I can say that every time
> I have asked a plant-knowledgeable person about our smartweed, they felt it
> was the invasive type.
>
> I think in my haste to get this posted before a Grounds meeting I relied
> on a google entry that told me that PA smartweed was invasive so I thought
> that was the one we have.
>
> I guess I need to affirm that my ocrea is not bristled.
>
> Assuming ours is the invasive species, if you have guidance on whether
> mowing is worsening the problem, please let me know.
>
> Thanks,
> Lori
>
>
>
>   On Monday, July 13, 2015 4:40 PM, Art Gover <aeg2 at psu.edu> wrote:
>
>
> I like PA smartweed.  It’s native and charming and fills space.  Sure
> about the ID?
>
> Be well.
>
> Art
>
> Penn State Wildland Weed Management
> 116 ASI Building
> University Park, PA  16802
>
> (814) 863-9904
> (814) 863-7043 FAX
> http://plantscience.psu.edu/wildland
>
> > On Jul 13, 2015, at 16:37, frazmo <frazmo at gmail.com> wrote:
> >
> > Any thoughts out there in MAIPC land? If possible, copy the asker,
> lrbowes2 at yahoo.com, directly also as I'm not sure she's on our list.
> Cheers, Steve Young
> >
> > ---------- Forwarded message ----------
> > From: "lrbowes2 at yahoo.com [NativePlantseast]" <
> NativePlantseast at yahoogroups.com>
> > Date: Jul 13, 2015 12:34 PM
> > Subject: [NativePlantseast] Smartweed management?
> > To: <NativePlantseast at yahoogroups.com>
> > Cc:
> >
> >
> >
> >
> >
> > My community has an abundance of Polygonum pensylvanicum on a turf
> hillside that abuts a stream (on the other side of which is a wooded area)
> and a terraced native plant area (with asters, goldenrods, grasses,
> viburnums, violets, etc).  The Polygonum is thriving amongst the turf and
> is constantly invading the native plant terrace.
> >
> >
> >
> > We have some flexibility in how we manage the turf hillside in terms of
> mowing.  Can anyone offer some thoughts or guidance?
> >
> >
> >
> > I haven't found much on the web in the way of guidance for this topic.
> >
> >
> >
> > Thanks,
> >
> > Lori
> >
> > Arlington, VA
> >
> >
> > __._,_.___
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-- 
Jake Hughes
Lead Biological Science Technician
Shenandoah National Park
3655 US Hwy 211 E
Luray, VA 22835
Jake_Hughes at nps.gov
Office: 540-999-3500 ext 3492
Fax: 540-999-3697
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