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
Not Yet Rated

Monday - November 09, 2009

From: Austin, TX
Region: Southwest
Topic: Invasive Plants
Title: Removing three-seeded mercury in Austin
Answered by: Barbara Medford

QUESTION:

How can I get rid of Three Seeded Mercury (Acalypha phleoides)? Even if I try to dig it up, the roots go down forever and it ends up just breaking at 6-8" down. Just breaking it off at the surface, makes it grow even lusher. I've been trying for years to get rid of it and it's just spreading and taking over more of the yard. The "yard" is horse herb (aka straggler daisy) and other plants that come up that I like. I don't mow. I just pull out what I don't like. But this one weed is defeating me.

ANSWER:

Well, you may have to learn to like Acalypha phleoides (shrubby copperleaf), or be more aggressive. It is native to this part of the state, and therefore very adapted to the rainfall, climate and soil. Since it is perennial, just pulling it off the root is not going to stop it from coming back up, as you have already pointed out. You can't spray it with herbicide, as it would kill all the other dicots or broad-leaved plants (like the straggler daisy) that you already have. If you buy a spray that is for monocots, or grasses, it won't bother the three-seeded mercury, but it could kill some native grasses that you have been cultivating.

The first thing to do is make sure it never has an opportunity to go to seed. Even though it is a perennial that can come up from the roots, it will also propagate itself by the seeds on those tall bracts. This might be a time to break your rule about never mowing; if you mow it before it can seed, and keep mowing it as it sends up more bracts to try to seed again, you might just wear out the food stored in the roots. Doing this for several weeks when the plant is trying to bloom, and thus set seed, could greatly alleviate your problem. 

Beyond that is the somewhat labor-intensive, hands and knees on the ground, method of painting the cut stem with a wide spectrum herbicide. Begin with a small bottle of the herbicide and some disposable sponge brushes. Cut each stalk off near the root and quickly, within five minutes before the stalk starts to heal over to protect the roots, paint the cut edge with the herbicide. Be very careful, spilling this could contaminate the soil and kill the other plants, broad-leaf and grasses, and don't spray, for the same reason. This plant is monoecious, which means it has both male and female flowers on each plant, and each plant can carry on creating more plants with no outside help. 

From our Native Plant Image Gallery:


Acalypha phleoides

Acalypha phleoides

Acalypha phleoides

 

 

 

More Invasive Plants Questions

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

Use of non-native pothos for outside wall from Las Vegas NV
January 05, 2014 - I am in Las Vegas, NV. I live in a cottage-style apartment so I have a north facing porch with no one on the west so I get some there (and have an inherited cactus probably a yard all round) I would ...
view the full question and answer

Non-native, and/or invasive bermudagrass, St. Augustine and Pistache from Houston
September 24, 2012 - Our St. Augustine lawn died suddenly this summer from either chinch bugs or grub worms (or both?), and a multitude of weeds and native Bermuda have taken over the area. Now that the weather has cooled...
view the full question and answer

Problems with recently planted trumpet vine from Worcester MA
October 20, 2012 - Dear Mr. Smarty Plants, I have a question about my recently planted Trumpet Vines. First of all, I live in Massachusetts, zone 6. The soil is perfect for the two vines, which I bought from a local nur...
view the full question and answer

Sheet mulching before planting Habiturf from Grand Prairie, TX
March 03, 2014 - Have you tried sheet mulching as a bed prep and to kill bermuda grass before planting habituff?
view the full question and answer

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