Re: OT - Thistles

Marte Halleck wrote (20 June 97):
> Has your part of NMx been overrun by the 6'-7' monster 
> >Canadian (or Musk) thistles? 

To which John Montgomery replied (20 June 97):
> My goodness, I am glad that Canada Thistle doesn't grow to that size in
> Canada.
> Are you sure that isn't a Texas Thistle?  :-)


The inappropriately named *Canada* thistle (Cirsium arvense) is actually a
Eurasian native, as are most of our troublesome weeds. In my book of
(British) Wildflowers its common name is given as Creeping Thistle. (BTW,
this book might equally well have been titled *North American Weeds*, as it
features such choice items as knapweed, orchard grass, common yarrow,
goatsbeard, sowthistle, henbane, knotgrass, and field bindweed (!!!!),
among other glories of the British flora).

Around here Canada thistle does not grow taller than 3 to 3 and 1/2 feet,
but as the name creeping thistle implies, it is an aggressive underground
spreader. There was a patch of it growing along a fence line in an area
that I prepared for planting iris last year. I sprayed this area with
Roundup to get rid of field bindweed last summer. The Canada thistle was
unaffected by this spray. During the winter their was some discussion of
Canada thistle on iris-l, and I learned that the proper time to spray
Canada thistle with Roundup is in the spring when the growth is 3 to 6
inches high. I followed this recommendation with complete success. 

My previously mentioned Wildflower book also includes Musk Thistle (Carduus
nutans), but I don't know if the same species would have the same common
name in Colorado. The only thistle growing around here that I have seen get
6 to 7 feet tall is Scotch Thistle (Onopordum acanthifolium).

BTW, John, what do they call Canada thistle in Canada?

Jeff Walters in northern Utah  (USDA Zone 4, Sunset Zone 2)
cwalters@cache.net
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