Re: OT - Thistles/Burrs

At 06:10 AM 6/23/97 -0600, Rima wrote:
  But the large leafed plant that gets smallflowers and
>terrible burrs arevery invasive and cause havoc, especially if youhave
>dogs.  One of mine, when a pup, came home foaming at the mouth and the
>vet found a throatfull ofburrs and a very torn-up mouth (labs are
>wonderful but sometimes nottoo bright).
==================================================

This sounds like what we call burdock. a nuisance because animals can
spread it very easily (not usually by mouth though). It has a tap root
which means it stays in place unlike the Canada Thistle which will spread
underground for long distances, making it very hard to eradicate except by
systemic herbicide.

I do not have a copy of the CD mentioned by Ian but for what it is worth,
here is how we try to control Canada Thistle. I use 2% roundup solution and
try to apply it in early fall, Sept. here. At that time I believe the sap
pressure tends to be less strong, allowing the roundup to circulate through
the root system more readily. Another time when it seems quite vulnerable
is just as buds have formed.
The 2% solution will kill the top growth at any time of the year but it
seems to kill the massive underground root system best in early fall. I
gained my experience with this weed in the school of hard knocks, having
rented land that was a thistle factory for years. It is an ongoing fight
due to the huge seed bank which had built up in the soil.
By the way, research has shown that the roots of this thistle produce a
chemical which is in effect it's personal herbicide, preventing or slowing
the growth of nearby plants. 
Tilling or digging seem to be more effective as a means of propagation than
of eradication. This leads me to wonder how come the farms of our ancestors
were not completely overrun. Did they know something which we don't?
Cheers
John Montgomery
monashee@bcgrizzly.com
Vernon  BC  where I am getting the upper hand with thistles and am now
nervously watching a tidal wave of Convolvus arvensis moving up the hill
toward our place. This one I believe is even tougher to control.
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