Rent Shop Volunteer Join

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.

Help us grow by giving to the Plant Database Fund or by becoming a member

Did you know you can access the Native Plant Information Network with your web-enabled smartphone?

Share

Ask Mr. Smarty Plants

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

Search Smarty Plants
See a list of all Smarty Plants questions

Please forgive us, but Mr. Smarty Plants has been overwhelmed by a flood of mail and must take a break for awhile to catch up. We hope to be accepting new questions again soon. Thank you!

Need help with plant identification, visit the plant identification page.

 
rate this answer
1 rating

Monday - July 28, 2008

From: Chicago, IL
Region: Midwest
Topic: Invasive Plants
Title: Getting rid of Polygonum punctatum (dotted smartweed)
Answered by: Nan Hampton

QUESTION:

Dear Mr. Smarty Plants, After much online research, my property has been invaded by what I believe to be Persicaria polygonum punctata, more commonly known as dotted smartweed. I have tried horticultural vinegar but it only curled the leaves. Additionally, I have read that horticultural vinegar detrimentally changes the soil. These plants become at least three feet tall so it's hard to spray all parts of it. I have thought of covering them with clear plastic sheeting but don't know if that is enough heat to kill the roots. I feel my last resort is glyphosate, of which I have heard pros and cons. Digging them out is as horrendous as trying to comb out knotted hair and I do not have the time nor energy as they are everywhere. As I have said, I have been all over the Web looking for an answer as to how to kill these plants. Do you have any suggestions? I would really appreciate any advice you can provide. Jo

ANSWER:

I assume you mean Polygonum punctatum var. punctatum (syn.=Persicaria punctata)(dotted smartweed), a plant native to North America. Another common name is water smartweed. Or, are you talking about Polygonum persicaria (spotted ladysthumb). This is an introduced species. Whichever one it is, the treatment will be the same. The most environmental friendly way, of course, would be to dig them out or pull them up. Alternatively, instead of spraying them you can cut them off near the ground and carefully paint or inject the cut stalk with herbicide. This would put the herbicide where it would do the most good and would be the least harmful to other plants and to the environment. If you spray them, you run the risk of harming other plants nearby that you want to save. Consult with the Cook County Extension Service or visit a reputable garden nursery for advice on the best herbicide to use. Please read carefully all instructions that come with the chemical and follow the safety guidelines to protect yourself and the environment.
 

More Invasive Plants Questions

Growing kudzu in Las Vegas NV
April 18, 2013 - Hi Mr. Smarty Plants, I have a question about a known invasive species that I know you advise against, but I feel my situation may be different enough that it's worth asking about. Yes, I'm talk...
view the full question and answer

Cutting back Pampas grass.
March 27, 2009 - When and how much should I cut back Pampas grass in the Hill Country of Texas.
view the full question and answer

Creeping buttercups in juniper in McKeesport PA
May 22, 2010 - I have creeping buttercups in my juniper ground cover. How do I get rid of them.
view the full question and answer

removing paper mulberry shoots from lawn
August 09, 2011 - Dear Mr./Ms. Smartypants, I recently moved into an Austin home with the backyard taken over by paper mulberries. There were originally 2-3 large bush/trees, but now that I've removed them I realiz...
view the full question and answer

Native plants for shade in Ennis TX
August 26, 2011 - My house faces south. The southwest side of the front yard has a Pride of Houston, Japanese Barberry, 2 crape myrtles and some dwarf yaupon hollies. The other section, divided by a stairway to the p...
view the full question and answer

Support the Wildflower Center by Donating Online or Becoming a Member today.