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Canada Thistle/L.Sullivan

Lawrence:
     In response to your additional questions to me, I can offer the
following.  Your idea of seeding Big Bluestem and Indian Grass into patches
of Canada Thistle is good!  If such patches have many native forbs, I would
lightly disk the patch and hand seed followed by raking to cover seeds (in
early spring).  If the patch has few or no native forbs, I would spray the
patch with a 2,4-D derivative, then seed as above.  Regarding my preference
for the type of 2,4-D derivative, the most efficacious (albeit, one of the
most expensive) in my experience has been Chaser Turf Herbicide (United
Horticultural Supply) but less expensive 2,4-D derivatives (esters and
amines) are also effective on this alien plant.  You mentioned Roundup (I
use Roundup Ultra with no additional chemical additives).  It is more
effective on Canada Thistle then are the 2,4-D derivatives but, obviously
will kill your native C4 grasses.  Applying Roundup to single individual
plants of a clone of Canada Thistle, while conceptually attractive, in my
experience has not been effective.  You are correct, "after 3 to 4 years it
will be self sustaining" is rarely ever true; such is profoundly influenced
by the amount and type of non-native plants and the soil type.  Success to
you!
Cliff
(Clifford W. Welsch)
P.S. Parenthetically, the UW-Madison has always been one of my favorite
academic institutions; during my medical career in Michigan I was fortunate
to be invited to the UW-Madison campus on a number of occasions to lecture
in the medical field, a dynamic institution to say the least!


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