Re: control of Knapweed

A little patch of knapweed can get bid in a hurry! I've heard
Knapweed does poorly in HEAVILY irrigated areas.  The only other
chemical approach is using Tordon, which is very persistent and
toxic.  We've been mowing it to try to  reduce the  seed bank (seed
remains vital for seven years) and are experimenting with tillage
followed by competitive grass and legumes.

I've virtually eliminated knapweed on our drainfield (which used to
grow six feet tall and was VERY dense) by tilling it and seeding it
to a dryland alfalfa and crested wheat grass.  The inoculated
alfalfa established a good stand, and some wild mustard took hold
too, leaving virtually no room for the knapweed.  I was not only
pleased but surprised by the results because knapweed is such a
strong competitor.

I've had more mixed results in drier pasture lands.  We live 20
miles east of Helena, Montana in a 9-12" annual precip zone.  Our
county is going to try using a steam weed burner this year for the
first time.

Controlling knapweed is more realistic than eradication,
particularly if you choose to use less toxic, persistent herbicides
like 2,4-D or Roundup.  Timing will be crucial.  Whatever you do,
even if it's pulling it by hand, DO IT soon and regularly and stay
at it.  In our community, I've heard of folks spraying for 5 or more
consectuiveyears trying to eradicate knapweed.  I think this is
often done in absence of a planned succession of competitive

Good luck, you'll need it.
Al Kurki, Canyon Ferry, MT

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