What is the horrible smelling invasive weed? - Ask Extension
And how do I kill it? This plant grows like crazy in spring and summer. It used to be in a small patch of isolated grass near the driveway 8 years ago...
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What is the horrible smelling invasive weed? #242499
Asked May 07, 2015, 2:34 PM EDT
And how do I kill it? This plant grows like crazy in spring and summer. It used to be in a small patch of isolated grass near the driveway 8 years ago when we bought our house. It has now jumped to a second separate isolated patch of grass. We rented out our house from 2010-2014 and during that time, the weed has taken over the rest of the yard which is landscaped or natural around the perimeter of the yard, with lawn in the center. The whole lot is 1 acre. It has not yet circumvented the yard, but it won't be long until it does. This weed has more roots than anything I've ever seen. They are white and about as thick as bean sprouts. The plant smells like acrid tobacco, and you can smell it when you walk by it. It has purple veins and the leaves are edged in purple. I have use Roundup for brush clearing, dug it up, covered it with plastic during the winter after having poisoned it and dug up as much as I could and it STILL grows back in the spring. By the end of the summer, it has grown up around and nearly strangled the ferns, and all of the perennials I have planted. It grows to be about 8" tall.
Montgomery County Maryland
Expert Response
This is an alien invasive plant, commonly known as Japanese knotweed (polygonum cuspidatum).Also known as Fallopia japonica (botanical names are changed sometimes).
Here are some images: http://leavesofplants.blogspot.com/2012/09/polygonum-cuspidatum.html There is some variation among plants, but if you Google Image it you'll see many similar photos.
Don't despair. This plant is horribly invasive, as you know, but it can be controlled with constancy and persistence. There is a video about it in our website: http://extension.umd.edu/hgic/problems/invaders-video-series Select the Japanese knotweed one.
Here is information from one of the best resources available:http://www.nps.gov/plants/alien/fact/faja1.htm As it mentions, to be sure that the herbicide adheres to the leaf well, mix a surfactant with the herbicide. (It makes it stickier.)
We should add that timing can be very important with hard-to- kill plants. In fall, plants transport carbohydrates to their roots to store and then use for energy to regenerate the next spring. If you spray it twice with a 3 week interval, beginning in late summer/early fall, you may have the best success.
Also, each time you cut it and it has to regenerate, it depletes the stored energy in its root system. And if you cut it, let it regenerate just a little and then spray that new foliage, you are giving it a double whammy.
Though you have a big challenge, congratulations for taking on an alien invasive plant. These invaders are doing terrible damage to our parks and natural areas.
ECN
Here are some images: http://leavesofplants.blogspot.com/2012/09/polygonum-cuspidatum.html There is some variation among plants, but if you Google Image it you'll see many similar photos.
Don't despair. This plant is horribly invasive, as you know, but it can be controlled with constancy and persistence. There is a video about it in our website: http://extension.umd.edu/hgic/problems/invaders-video-series Select the Japanese knotweed one.
Here is information from one of the best resources available:http://www.nps.gov/plants/alien/fact/faja1.htm As it mentions, to be sure that the herbicide adheres to the leaf well, mix a surfactant with the herbicide. (It makes it stickier.)
We should add that timing can be very important with hard-to- kill plants. In fall, plants transport carbohydrates to their roots to store and then use for energy to regenerate the next spring. If you spray it twice with a 3 week interval, beginning in late summer/early fall, you may have the best success.
Also, each time you cut it and it has to regenerate, it depletes the stored energy in its root system. And if you cut it, let it regenerate just a little and then spray that new foliage, you are giving it a double whammy.
Though you have a big challenge, congratulations for taking on an alien invasive plant. These invaders are doing terrible damage to our parks and natural areas.
ECN
On the other hand....
if this plant never gets over 8" (we were assuming that it's staying short because you keep hacking at it), then it may be something else. The same principles of controlling hard-to-kill plants would apply to your plant as apply to Japanese knotweed. Remember that glyphosate is a total vegetation killer, so use a shield of cardboard or plastic to keep it from contacting your desirable plants.
We hope you don't have Japanes knotweed, since it is so difficult to manage. If your plant ever blooms, the blooms would be able to help us give you a positive id. It
ECN
if this plant never gets over 8" (we were assuming that it's staying short because you keep hacking at it), then it may be something else. The same principles of controlling hard-to-kill plants would apply to your plant as apply to Japanese knotweed. Remember that glyphosate is a total vegetation killer, so use a shield of cardboard or plastic to keep it from contacting your desirable plants.
We hope you don't have Japanes knotweed, since it is so difficult to manage. If your plant ever blooms, the blooms would be able to help us give you a positive id. It
ECN
Ok, but that's not what it is. Further research by my sister has brought us to a picture of Houttuynia cordata. As it turns out, that's what it is. So do you know how we would get rid of Houttuynia Cordata?
Houttuynia is hard to eliminate. Repeated painting with glyphosate will be necessary. Use the same methods to get rid of Houttuynia as Japanese knotweed. You could try tryclopyr to see if it is more effective than glyphosate. Persistence is the key to getting rid of any invasive. vw
Thank you very much. Not great news, but at least there is a chance of getting rid of it. Should I try the glyphosate now, or do as you suggested with the Japanese knotwood and start late summer early fall?
Houttuynia does have the tendency to
become invasive due to underground spreading rhizomes and needs to be
controlled. This will require persistence on your part and there are no easy answers.
You can spray the foliage now or paint with an herbicide that contains glyphosate, such as Round-Up. The foliage of your ornamental plants would need to be protected because glyphosate is a non-selective herbicide and will kill any plant that gets the chemical on its leaves. You will most likely get regrowth during the growing season. Be prepared to spray the regrowth again in the fall.
Do not expect to achieve complete control in one season. You will have to monitor in the following spring and fall seasons for any regrowth and control.
mh
You can spray the foliage now or paint with an herbicide that contains glyphosate, such as Round-Up. The foliage of your ornamental plants would need to be protected because glyphosate is a non-selective herbicide and will kill any plant that gets the chemical on its leaves. You will most likely get regrowth during the growing season. Be prepared to spray the regrowth again in the fall.
Do not expect to achieve complete control in one season. You will have to monitor in the following spring and fall seasons for any regrowth and control.
mh
Thank you, you've been most helpful!
