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Q. Who is Mr. Smarty Plants?

A: There are those who suspect Wildflower Center volunteers are the culpable and capable culprits. Yet, others think staff members play some, albeit small, role. You can torture us with your plant questions, but we will never reveal the Green Guru's secret identity.

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Ask Mr. Smarty Plants is a free service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center.

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Sunday - March 20, 2011

From: Muskogee, OK
Region: Southwest
Topic: Non-Natives
Title: How to eradicate non-native invasive Houttuynia cordata from Muskogee OK
Answered by: Barbara Medford

QUESTION:

I have planted a very invasive plant called houttuynia and cannot get rid of it! It is very stinky and the stems break off easily at the roots. I cannot dig it up anymore - it is all over in my flower bed! Do you know of something I can spray on it to eradicate it - and not kill my other flowers!?

ANSWER:

Since this plant is native to southeast Asia, we have no information on it in our Native Plant Database. However, we are always interested in controlling or eliminating invasive plants, native or not. From a website by Ohio State University, we found this article on Houttuynia cordata, which indicates, among other things, that is is invasive because it spreads by underground rhizomes which, even if a small fraction is left in the soil, can still continue propagating. A wonderful argument for investigating the habits and nativity of any plant before you plant it.

Please, no spray! One of the things you will learn when you read the above link is that it seems to be resistant to many herbicides. We have a more or less standard operation that we suggest for trying (notice we said trying) to control invasive plants. Any spray you try will probably not faze the invasive, but will lay waste to all the broadleaf plants around, including your ornamentals. Buy some wide-spectrum herbicide and some small sponge disposable paintbrushes. Clip off every stem you can find emerging from the soil and then, quickly, within 5 minutes, paint the cut stub with the undiluted herbicide. You must do this right away because the stem will quickly begin to heal over to protect the rhizomes beneath. Of course, don't allow the plant to bloom and keep all leaves cut off in order to deny those rhizomes of the food they get from the leaves. Theoretically, in a perfect world, that would cause the rhizomes to starve to death. However, the way that plant became so invasive is by being very tough and adaptive, so you can't let up. Apparently, the plant is somewhat dormant in the winter, so that would be a good time to really make a digging assault on the rhizomes and be sure to dispose them where they won't root again! But you must persist and keep after the plant, constantly looking for sprouts in places you didn't expect it to be.

 

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