Contact Us Host an Event Volunteer Join

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
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 Problem Plants Questions

Invasive native wild onions in East Granby CT
May 17, 2011 - I have wild onions which have become extremely invasive. I have no idea how to get rid of them, and this year they seem to have taken over my entire flower bed. I tried pulling the bulbs out for sever...
view the full question and answer

Poison Ivy in Semi-wetland Massachusetts
June 27, 2013 - You answered this question for Tennessee, but I would like an answer for a Massachusetts semi-wetlands area: What can I plant to discourage poison ivy, or at least make it very clear that it is poison...
view the full question and answer

Elimination of non-native English ivy in Maryland
March 11, 2009 - I have Old English Ivy sprouting up throughout my side yard. What can I do to get rid of it? Would putting lime down help or Crabgrass control? What would you suggest and the easier the better as I...
view the full question and answer

Controlling Triadica sebifera (Chinese tallow tree)
July 20, 2013 - We are trying to remove Chinese tallow trees from the lake bed on Lake Buchanan. We cut them down, but they grow back from the roots. They are very hard to dig out. Do you have any suggestions for how...
view the full question and answer

Getting rid of skunk cabbage in Hopedale OH
April 22, 2010 - How can someone get rid of skunk cabbage?
view the full question and answer

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