En EspaŅol
Share

Ask Mr. Smarty Plants

Mr. Smarty Plants - How to tell the difference between native and European thistles

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

Controlling seeding of non- native, invasive Paulownia from Fayetteville TN
August 17, 2012 - My husband planted a Paulownia tree against my advice about eight years ago. This summer it has huge seed pods. How do I keep the seeds from invading the wooded area of our property?
view the full question and answer

Non-native and invasive bamboos from Staten Island, NY
May 19, 2013 - Hi I put some black Bamboo and some bias Bamboo in a large container about 6ft by 2ft and ht 18 inches .How can I get this Bamboo to thrive ? Suggestions on types of plant food or fertilizer or ant t...
view the full question and answer

Flashing barrier to Bermuda in tree bed
September 16, 2007 - I'm building a 6-ft-diameter planting bed on a gentle slope on blackland clay, at the center of which I plan to install a cedar elm. I'm using the wedge-shaped stones from the home-improvement stor...
view the full question and answer

Identification of plant with orange sap that glows at night
June 06, 2012 - I was just pulling up a plant and noticed that its sap was a kind of orange then I noticed it glowing orange at night. What kind of plant is this and is it dangerous?
view the full question and answer

Poverty plant overgrown in Austin
June 06, 2012 - We have a poverty plant that is too big for its space in our yard. We like it and want to keep it. Can it be transplanted easily? What about pruning it.
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
© 2014 Lady Bird Johnson Wildflower Center