On Wed, 26 Jun 2013 17:48:30 +0000 (UTC), Drew Lawson wrote:
In article
Kay Lancaster writes:

I made the mistake of ignoring them. They got well established in
the area that I just returned to a vegetable garden this year. I
tilled, which broke up the underground network (or most of it), but
I still have to get the survivors before they have a chance to
reestablish it.

But till & trowel isn't an attractive solution if they are in the
lawn.

If it's not a stoloniferous plant (which means that every fragment in the
soil has the chance of becoming an entirely new plant), then the easy way,
imo, to deal with thistles in lawn is with an old fashioned dandelion digger
like: http://www.gardentoolcompany.com/lon...r-by-sneeboer/
Cut across the taproot an inch or so under the soil surface, and then
either flip the top of the plant over to desiccate in the sun (and get mulched
with the next mowing a few days later), or pick 'em up with a pair of
long tongs like a "reacher" http://www.spinlife.com/Nova-PIKSTIK...a#.UdJWLXwbDMU or bbq tongs and toss them into a wheelbarrow or cart or tarp for drying and
then composting.


I control it here in my Oregon yard with heading the flowers**
as soon as I see them, and spot applications of glyphosate on
established plants in the fall. Heading has to be done vigilantly--
at least once a week.

I never had much success with glyphosate. (I keep it on hand for
poison ivy and a couple other special cases.) I attributed that to
the root network.

Most herbicides, but especially things like glyphosate and gluofsinate,
where the herbicide is inactivated after a short period,
work best if the plant is in an active stage of growth... temperatures
neither too hot nor too cold, enough water to be growing and not stalled
out, etc.

You can also run into problems with the wrong concentration
or wrong timing of application, or with too much applied so the herbicide
runs off the plant, or if the plant has a really waxy cuticle, like English
ivy. Too strong a concentration is just as bad as too weak... often, if
the concentration is too strong, you get the top growth killed back, and
the herbicide is not transported to the basal parts of the plant, so they
can regrow. If you're dealing with a waxy cuticle, a spreader-sticker
like Aerosol OT (sodium dioctyl sulfosuccinate) or even a few drops of
dish detergent, can improve things dramatically.

Droplet size, if you're
spraying, can be important, too... too small a droplet may not get through
a heavy coat of plant hairs like many of the thistles, while too large a
size can roll right off the leaves, doing no damage. Yet another way
to goof things up with glyphosate application, is to dilute the spray with
dirty water -- I saw the results of someone spraying 250 gallons (!) of
glyphosate diluted with water taken from an irrigation ditch. Did absolutely
nothing because there was enough suspended clay particles in the water
to inactivate the herbicide.

And before you decide I'm a devotee of spray and pray pesticide
applications, I used to help with the botany end of a university weeds
class, and got to see examples of why it's best to id the weed first, then
consult the detailed instructions on controlling that species. It's
pretty rare for me to use an herbicide, but there are some things that
there's just no economically or labor-feasible way to control otherwise.

One end of the yard is a garden with Canada thistle, the other end
is lawn with Bermuda grass (the undesirable sort).

I have a way of attracting invasive weeds, I suppose.

Ooh, you did get lucky with that, didn't you? All you need is some
johnsongrass for a real trifecta there!

Kay