Host an Event Volunteer Join Tickets

Support the plant database you love!

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 - April 01, 2013

From: Brisbane, Australia
Region: Other
Topic: Invasive Plants, Non-Natives, Problem Plants, Herbs/Forbs
Title: Dietes bicolor invasive from Brisbane Australia
Answered by: Barbara Medford

QUESTION:

We have dietes bicolor growing in our garden. I am changing the type of garden and cannot seem to kill it. I've dugged it out, spent too many weekends pulling out every new shoot, used poison, but to no effect. I cannot replant this garden until I can get rid of this plant. Any suggestions?

ANSWER:

We are at something of a disadvantage in trying to answer your question. The Lady Bird Johnson Wildflower Center (home of Mr. Smarty Plants) is committed to recommending the growth, propagation and protection of plants native to North America. Dietes bicolor (African iris) is native to, well, South Africa, and therefore  to neither North America nor Australia. It is widely grown in Central Texas, though of course not at the Wildflower Center. Since we have no experience with it, we were not aware of any tendency to invasiveness. The main problem in getting rid of it is that its root are rhizomes.

Rhizomes are horizontal underground stems that strike new roots out of their nodes, down into the soil, and that shoot new stems out of their nodes, up to the surface. This rhizome activity represents a form of plant reproduction. The irrepressible nature of much of the vegetation you'll find on invasive plants lists is due to the vigor of the rhizomes of these aggressive plants.

Looking at these images of rhizomes will help you understand how difficult your task may be. If the plants you have in your garden are not too large, you may be able to dig out the whole network of roots in one mighty shovelful, but probably not.  After removing as much as possible, and discarding the clump of dirt with the rhizomes in it where they roots won't be able to reproduce yet again, try to kill any remaining portion of the rootlets left behind. Our practice in getting rid of plants that obnoxious is to obtain a small bottle of a wide spectrum herbicide that will kill just about anything, along with some small sponge disposable paintbrushes. If you find a small new plant coming up, cut it off as close to the soil as you can, and then paint the cut root end with some of the herbicide. You must do this quickly after cutting before the rhizome heals itself over to protect the rest of the plant. Properly administered, that herbicide should be able to destroy at least that little fragment of the plant. Prepare to repeat this many times before the rhizomes finally are defeated.

 

More Herbs/Forbs Questions

Garden instructions from Austin
June 12, 2013 - I'm a beginning gardener putting in some new landscaping in my front yard in north central Austin, TX. The yard faces almost due east, so it gets full sun until early afternoon, when the house's sha...
view the full question and answer

Native plants for city lot in Longview, TX
March 19, 2008 - Just bought a city lot in Longview, TX and want to put in some plants at the periphery even before the house is built. Can you recommend any that would be from your list of East TX plants that are pa...
view the full question and answer

Root rot and transplant shock in Texas betony
July 13, 2006 - Texas betony is supposed to be drought resistant but also likes to be kept moist, but I have had trouble getting it established. These seem to be undemanding plants I have had entire stems dry up and...
view the full question and answer

Best time to plant wetland plants in NY
April 19, 2010 - Hello Mr. Smarty Plants - I'm working on a fresh water, shoreline wetland creation project in New York State. I've created two zones of native wetland plantings, an emergent shallow marsh zone ...
view the full question and answer

Restoring tornado-damaged property in Alexander City AL
January 29, 2012 - Dear Mr Smartypants, We were struck by the outbreak of tornadoes last spring and our wonderful woods are now unsightly sloping pastures with erosion problems.. many stumps and coils of roots. We are...
view the full question and answer

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