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?

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
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

Tuesday - April 19, 2011

From: San Marcos, TX
Region: Southwest
Topic: Invasive Plants
Title: How to tell the difference between native and European thistles
Answered by: Nan Hampton

QUESTION:

How can I tell the difference between invasive (European) thistles and thistles that are native to Texas? And what is the best way to eradicate the invasive varieties?

ANSWER:

According to the USDA Plants Database there are six different genera of plants that occur in Texas that have species with 'thistle' as part of their common name.   Some of the species in those genera are native and others aren't.  All of them, even those that are native, have been listed by at least one state as noxious. They are: 

Centaurea melitensis (Maltese star-thistle)—non-native and noxious, appears on the Texas Invasives Database.  You can see a description of two of the species below from eFloras.  Occurs in Hays County.

Silybum marianum (blessed milkthistle) non-native and noxious.  You can see a description of this species at eFloras.  Occurs in Hays County.

Carthamus lanatus (woolly distaff thistle) non-native and noxious.  You can see a description of this species at eFloras.  No record in or near Hays County.

Onopordum acanthium (Scotch cottonthistle) non-native and noxious, appears in the Texas Invasives Database.  You can see a description of the species in eFloras.  No record in or near Hays County.

Cirsium sp. You can see the descriptions of the species below from eFloras.  (Note:  Arkansas and Iowa have put all Cirsium spp., native and non-native, on their Noxious Weeds lists):

  1. Cirsium altissimum (tall thistle)—native and noxious.  No record in or near Hays County.
  2. Cirsium carolinianum (soft thistle)—native and noxious.  No record in or near Hays County.
  3. Cirsium engelmannii (Engelmann's thistle)—native and noxious.  No record in or near Hays County.
  4. Cirsium horridulum (yellow thistle)—native and noxious.  Occurs in Hays County.
  5. Cirsium x iowense—native and noxious [cross between C. altissimum and C. discolor]
  6. Cirsium muticum (swamp thistle)—native and noxious.  No record in or near Hays County.
  7. Cirsium ochrocentrum (yellowspine thistle)—native and noxious.  Occurs in Hays County.
  8. Cirsium texanum (Texas thistle)—native and noxious.  Occurs in Hays County.
  9. Cirsium turneri (cliff thistle)—native and noxious.  No record in or near Hays County.
  10. Cirsium undulatum (plumed thistle)—native and noxious.  Recorded in Comal County, but not Hays County.
  11. Cirsium vulgare (bull thistle)non-native and noxious, appears on the Texas Invasives Database.  Occurs in Hays County.

Carduus sp. You can see descriptions of the species below on eFloras.  (All species appearing in Texas are non-native and considered noxious.):

  1. Carduus acanthoides (spiny plumeless thistle) non-native and noxious.  No record in or near Hays County.
  2. Carduus nutans (nodding plumeless thistle) non-native and noxious, appears on the Texas Invasives Database.  Reported by USDA as occurring in Blanco County, but not Hays County.
  3. Carduus pycnocephalus (Italian plumeless thistle) non-native and noxious.  No record in our near Hays County.
  4. Carduus tenuiflorus (winged plumeless thistle) non-native and noxious, appears on the Texas Invasives Database.  Reported by USDA as occurring in Travis County, but not Hays County.

Salsola sp.  You can see descriptions of the species below on eFloras:

  1. Salsola collina (slender Russian thistle) non-native and noxious.  No record in or near Hays County.
  2. Salsola kali (Russian thistle) non-native and noxious.  No record in or near Hays County.
  3. Salsola tragus (prickly Russian thistle)non-native and noxious, appears in the Texas Invasives Database.  No record in or near Hays County.

To summarize, assuming you are asking advice for the thistles that occur in Hays County, Cirsium horridulum (Yellow thistle), Cirsium ochrocentrum (Yellowspine thistle) and Cirsium texanum (Texas thistle) are native thistles that occur in Hays County and Cirsium undulatum (Plumed thistle) is a native that occurs in adjacent Comal County.

The following non-native thistles occur in Hays or adjacent counties:  Centaurea melitensis (Maltese star-thistle), Silybum marianum (blessed milkthistle), Cirsium vulgare (bull thistle), Carduus nutans (nodding plumeless thistle) occurs in adjacent Blanco County and Carduus tenuiflorus (winged plumeless thistle) occurs in adjacent Travis County.  The first two, Maltese star-thistle and blessed milkthistle, are relatively easy to distinguish from any of the native species in Hays County.  The other three may be a bit more difficult to distinguish from the natives, but the eFloras descriptions for each should help in determining which is which.  All of the invasives except Silybum marianum (blessed milkthistle) appear in the Texas Invasives Database with Management guidelines.  You can find information for managing Silybum marianum from King County (Washington) Noxious Weed Control Program.


Cirsium horridulum


Cirsium horridulum


Cirsium ochrocentrum


Cirsium ochrocentrum


Cirsium texanum


Cirsium texanum


Cirsium undulatum


Cirsium undulatum

 

 

More Invasive Plants Questions

Replacement of Arizona ash in Austin
October 28, 2011 - We have two Arizona Ashes in our yard that probably have maybe a decade left in them. We want to get a couple new trees started, so they will be well established once the Ashes are near their end. In ...
view the full question and answer

Aggressive vine with purple flowers in South Carolina
September 12, 2014 - Found an aggressive climbing vine with purple flowers in out vegetable garden. This garden was cleaned and new dirt, mulch and manure was put in in the spring. It was raked out after the infusion of d...
view the full question and answer

Planting petunias around base of oak tree from Houma LA
March 30, 2013 - I live in south Louisiana and I want to plant petunias. Can I plant petunias around the base of an oak tree?
view the full question and answer

Removing St. Augustine from flower beds
January 25, 2009 - We just had new landscaping put in at our house. We had planting beds prepped and mulched and had Zoysia sod installed outside the beds. The yard before had small areas of St. Augustine growing and no...
view the full question and answer

Removing non-native plants appearing in Austin in early spring
March 14, 2012 - In order to know which plants to keep and which to remove, is there a source to look up and identify common non-native plants that are seen in Austin about this time of the year (late winter, early Sp...
view the full question and answer

Smarty Plants's Facebook profile Support the Wildflower Center by Donating Online or Becoming a Member today.

Mr. Smarty Plants wants you to be his Facebook friend. Click the Facebook icon to add yourself to Mr. Smarty Plants list of friends.
E-NEWSLETTER | BECOME A MEMBER | DONATE NOW | MEDIA | SITEMAP | STAFF
© 2015 Lady Bird Johnson Wildflower Center