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Tuesday - November 26, 2013

From: Dripping Springs, TX
Region: Southwest
Topic: Invasive Plants, Non-Natives
Title: Advisability of growing Silybum marianum (Milk thistle)
Answered by: Nan Hampton

QUESTION:

I just received a load of clay-mix-dirt - and after our recent rains noticed the pile sprouting what looks like "Milk Thistle." Lots of them. The leaves are spiny and variegated - quite pretty. I was thinking I might translate a few to my native garden but I don't know much about this plant other than it is interesting looking. Would this be a bad idea?

ANSWER:

Silybum marianum (Milk thistle) is a native of Southern Europe, the Mediterranean area and North Africa. As an introduced species to North America it is considered invasive or, at the very least, a noxious weed in many areas. It is on the Arkansas Noxious Weeds List, the Oregon Noxious Weeds List and the Washington Noxious Weeds List. Here is a link from King County, Washington with information about its bad qualities. On the other hand, it is also praised for its herbal medicinal properties, but see also the Mayo Clinic reference. All in all, I would say it would be a pretty bad idea to grow milk thistle. First of all, it's not native to Texas nor even to North America. Second of all, it has the potential to be a problem plant if it escapes your flower beds and the seeds can be distributed by the wind. Why not get seeds of one or more of the Texas thistle species [Cirsium texanum (Texas thistle) or Cirsium horridulum (Yellow thistle)] to grow?

From the Image Gallery

Texas thistle
Cirsium texanum

Bristle thistle
Cirsium horridulum