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Stinky plant growing like crazy #869008

Asked May 18, 2024, 11:36 AM EDT

Is this plant invasive? It started to grow after the county installed an underground downspout extension for my neighbor. It is starting to grow into the yard and displace grass. It really stinks when we mow it.

Howard County Maryland

Expert Response

Yes, this is definitely an invasive plant: most likely Houttuynia Cordata sometimes called Fish wort or fish plant.

Here is some information from our website on how to eradicate this weed:

You will likely have to resort to using a systemic herbicide to kill the Houttuynia roots. Even though it can work well, repeat treatments will likely be necessary for established patches of this aggressive weed. Follow all label directions for the most low-risk, effective application of the chemical chosen. A product using the active ingredient glyphosate (the one common to Roundup) is probably your best bet, but we do not have local research as to which herbicide approach is the most effective.

Some herbicide products may allow for (or even encourage) the addition of a surfactant upon mixing a solution for application. Surfactants, also called spreader-stickers or adjuvants, are additives that help a herbicide adhere to the leaves (in this case) or work more effectively in other ways. Here, it would help a spray stick to the leaf long enough to be more fully absorbed instead of dripping off. These products are sold alongside pesticides in garden centers since the two are often combined for certain uses, though not every product benefits from their use, so always verify this with the label usage details.

Early autumn may be the most efficient time of year to attempt herbicide treatments, since the plant's deciduous leaves will be transporting more carbohydrates in the sap down into the roots for winter storage, and the absorbed chemical will then be able to "hitch a ride" more easily into the root system to cause dieback. Regardless of the time of year, plants successfully treated might not show obvious signs of dieback for days or even a week or more after application, so don't pull or dig them up until you're fairly certain they're dead.

Where the Houttuynia is mixed in with desired garden plants, you can try painting the glyphosate on the Houttuynia with a small foam paint brush after cutting down to the stem. Or spray, but use a shield of cardboard or plastic to keep spray off desirable plants. By doing this you would be less likely to apply the chemical on the desired plants. Then hand dig any of the remaining weeds that are not killed by the chemical.
I hope this is helpful....Robin

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