In message , Franz Heymann
writes

"Martin Brown" wrote in message
...

[snip]

A few very tough weeds with large deep roots and small tough waxy leaves
can survive it (and for some reason buttercup is partially resistant).

[snip]

Glyphosate is ever so slow in action compared to paraquat. I use both
according to my mood, and (because of my impatience?) I usually have to
apply glyphosate twice before the weeds keel over.

The second application is almost certainly wasted. Have more patience
and the weeds will keel over if you give them time for the waste
products of photosynthesis to build up. Green plants and glyphosate
don't mix.

Typically plants start to show serious signs of glyphosate damage after
about two weeks from application and it may take them another couple of
weeks to expire after that. And contrary to popular belief it may be
more effective to dilute the stuff to weaker than the recommended dose
(unlicensed use) so that it takes out more of the root system. Strong
sunshine, warmth and active growth speed the process up a bit.

Translocating weedkillers like glyphosate take a lot longer than
paraquat but have a more throrough effect. It takes time to permeate
deep roots.

Does paraquat really put paid to a plant, root and all, or does it only
interfere temporarily with the photosnthesis in the leaves?

Paraquat is much faster acting but is much more inclined to just burn
off the tops by excessive growth in the manner that Alan seems to think
glyphosate works.

It looks great for the gardener requiring instant gratification.

Regards,
--
Martin Brown