En EspaŅol

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?


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
Can't find the answer in our existing FAQs, submit a question to Mr. Smarty Plants.
Need help with plant identification, visit the plant identification page.
rate this answer
Not Yet Rated

Monday - July 28, 2008

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


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


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

Aggressive vine with purple flowers in South Carolina
September 12, 2014 - Found an aggressive climbing vine with purple flowers in out vegetable garden. This garden was cleaned and new dirt, mulch and manure was put in in the spring. It was raked out after the infusion of d...
view the full question and answer

Identification of lantanas safe for use in Florida
February 10, 2008 - Why do you list lantana camara as a native to the U.S. and as a native plant in Florida? It is a category one invasive exotic on the Florida Exotic Pest Plant Council's list of invasive exotics. La...
view the full question and answer

Avoiding planting Indian Paintbrush in Hawaii because of invasiveness
March 01, 2007 - My daughter is living in Hilo, Hawaii. For her birthday, her boyfriend ordered her some Indian Paintbrush seeds. Trying to be sure she grows them correctly in a pot, she found instructions that say ...
view the full question and answer

Nativity of Lantana camara and Strelitzia reginae
November 08, 2011 - I was wondering why Lantana Camara is not in the Wildflower's database. Multiple sources say it is native to the U.S. and North America. I was also wondering if Strelitzia reginae (Bird-of-Paradise...
view the full question and answer

Non-native mimosa failing to bloom in Leitchfield KY
October 29, 2011 - I have a medium size mimosa tree here in KY that usually blooms beautifully; it did not bloom at all this year. It leafed out well, needs a few dead limbs pruned, but seems otherwise healthy. Please t...
view the full question and answer

Smarty Plants's Facebook profile Support the Wildflower Center by Donating Online or Becoming a Member today.

Mr. Smarty Plants wants you to be his Facebook friend. Click the Facebook icon to add yourself to Mr. Smarty Plants list of friends.
© 2015 Lady Bird Johnson Wildflower Center