Host an Event Volunteer Join Tickets

Suppport 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
Not Yet Rated

Tuesday - May 26, 2015

From: Kerrville, TX
Region: Southwest
Topic: Invasive Plants, Managing Roadsides, Non-Natives, Problem Plants, Herbs/Forbs
Title: How to eliminate roadside thistles
Answered by: Guy Thompson

QUESTION:

When we drive along the highway we see lots of wildflowers and no thistles in the median. How does the Highway Department keep the thistles out? Here in Kerrville, we are overwhelmed by thistles this year. Any suggestions? Thank you.

ANSWER:

TXdot follows certain guidelines in planting and management of roadside wildflowers.  This includes waiting until seeds are set and ripened, mowing no lower than a certain height, and, in some cases, using herbicides.  Details of how areas containing thistles are treated are not available.  Thistles are not among the native species planted by the department.

There are several common thistles in this area, including the very invasive milk thistle and Malta star thistle, and the Cirsium texanum (Texas thistle).  Unfortunately, there is no easy way to eliminate these species.  Organizing a group to pull them up by the roots is effective but laborious.  This is the way it is done at the Wildflower Center.  Slicing off the tap root under the base of the plant with a spade makes this easier. A good pair of leather gloves is required to avoid the prickles.

Malta star thistle, the most invasive of the three mentioned, is an annual, so removing the seed heads before the seed mature is the next best thng to pulling up the entire plant.  But don't act too early in the season because the plant can quickly regrow new flowering stalks.

 

More Managing Roadsides Questions

Plantings of Castilleja in Texas
April 04, 2012 - I am a graduate student interested in studying different species of paintbrush (Castilleja) in Texas. I understand that the Texas Dept of Transportation has been seeding wildflowers along Texas highwa...
view the full question and answer

Native plants for roadside in Gallatin TN
February 19, 2012 - What native plant would you suggest that we try to establish on 100 feet of road frontage which gets full afternoon sun? The soil is mostly clay, and it's on a rather sleep hill about 10 feet high. ...
view the full question and answer

Managing Roadsides
March 20, 2004 - Id like to plant some wildflowers as part of a community or roadside project. Will you provide the seeds or grant money?
view the full question and answer

Digging wild buttercup from roadside in Mechanicsville MD
May 28, 2012 - Mr. Smarty Plants, is it illegal to dig out wild buttercup in Maryland? I see them along the dirt road or just in the ditch. Since buttercup considered weed, I'm wondering what the law say about this...
view the full question and answer

Life span of pin cherry (Prunus pensylvanica
May 12, 2015 - Do you have any data on the lifespan of pin cherry (Prunus pensylvanica) under urban conditions where is Not subject to seral succession (trees won't be permitted to overtake it)? On the other hand ...
view the full question and answer

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