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

Thursday - April 07, 2011

From: Mt. Pleasant, TX
Region: Southwest
Topic: Grasses or Grass-like
Title: Removing Purple Top Tridens out of Mt Pleasant Texas
Answered by: Leslie Uppinghouse


We would like to know how to kill these Purple Top Triden out of our garden. Thanks, Judy


We are guessing that you are looking to remove Tridens flavus (Purpletop tridens) out of a formal garden situation, because this grassy gem is highly coveted by Texans and a great native grass to add to the landscape. We will first talk about all the plusses with this grass in case you have a change of heart.

Purpletop tridens are lovely visually in mass from late summer through the fall. It is light, moves with the wind and has a deep pink color at the top. A great grass for a shady location as it is as happy in the shade as it is in the sun. Tridens hold the ground in place even in sandy soil and can take harsh soil conditions as in clay loam. A good grass for a leach field or areas that are hard to keep pretty. It does not require much water and if you look over the growing conditions in the link, you will see that it is listed as preferring dry soil. 

Livestock will consume it, so if you need it mowed, borrow your neighbors goat. A great hiding grass for nesting birds and also a favorite of many butterflies. A key larval host to skippers and wood nymphs.

Back to your original query. Tridens are not easy to get rid of. It holds the ground in place well, due to its fibrous and rhizomatous root system. Remove the grass now before the late summer seeding. As it is a perennial grass, the seed from last year has already set and the new grass should be showing. Now is the time to dig it up. 

You need to dig it out carefully. Be thorough enough to collect all of the roots and not leave behind the rhizomes. The goat idea isn't really as much of a joke as it sounds. One of the advantages of having a goat handle the first round of trimming is that the animal will consume any seed left on the grass. This would be a better option than mowing it down with a mower and then digging it out. If you don't have a goat handy, then dig it out tall but be careful not to shake out any seed still left on the plant from last season.

After you have dug everything out, if you feel confident that you have been thorough, till the dirt up then comb through the dirt again with your hands and pull out any small roots that have been left behind. Do not skip the digging step and head straight for the tiller. If you do, you risk chopping up the rhizomes and spreading the grass, rather than removing it.

Anytime you have to do any real digging, work smart, not hard. Wait for a good rain or water the area the night before you take on the project. You need the soil loose enough for you to remove all of the plant material without breakage. Having the soil moistened will make your life a lot easier enabling you to complete the task faster. Before you toss the Tridens out for good, look around your property for an area that has been hard to plant or a slope that could use some stability, it really is a very nice grass.

Tridens flavus



More Grasses or Grass-like Questions

Plants to stabilize sandy slope in Massachusetts
September 23, 2011 - Dear Mr. Smartypants, I am working on a small public housing project in Chelmsford, MA, northwest of Boston. We have a steep, sunny and SANDY slope and I am stumped as to what to recommend that wi...
view the full question and answer

Looking for a native turf grass for the Houston area
July 25, 2013 - Looking for a native turf grass for the Houston area. In some of your 2012 responses, you stated that "The good news is that research into turf-type grasses native to the coastal region is in the pla...
view the full question and answer

Plants to slow water runoff in Austin
April 16, 2011 - What native plants (rocky northwest Austin) will block water runoff? It seems as if something deep-rooted and densely growing would help. Grass comes to mind, but the area gets at best 2 or 3 hours of...
view the full question and answer

Recreating a wildflower meadow, central Texas
July 02, 2013 - We have an acre on our property that has bluebonnets. Unfortunately, it also has other plants that we don't want -Johnson grass, nettles, burrs. We plan to do a controlled burn in the fall and re-...
view the full question and answer

Need suggestions for native grasses to stabilize hillside Lago Vista, TX.
May 20, 2012 - I was hoping for some advice. We live on a hillside near Lake Travis. 10-12 years ago I removed all cedar trees. There is approximately 1-2 acrees of steep land between our residence and the lake. ...
view the full question and answer

Support the Wildflower Center by Donating Online or Becoming a Member today.
© 2015 Lady Bird Johnson Wildflower Center