Steve Firth writes:

Windmill wrote:
Does anyone know how long glyphosate takes to kill various weeds?
E.g. elderberry bushes, dockins, brambles, bracken, grass?

Don't want to waste money by spraying again if it's premature to do so.

Docks and grass about a fortnight if the weather is dry, brambles about a
month, elder bushes a couple of months depending on size. Bracken around
six weeks to two months it seems ver resistant to glyphosate and needs
several treatments possibly at monthly intervals.

The bracken looks slightly discouraged, but not much more than that.
Suppose I'll have to spray again. The elderberry is new growth and
seems now to be dying.

Also I would bump up the
concentration by 25-30% for elder and bracken. ie Instead of 120-150 ml of
360g/l concentrate per five litres use 150-200 ml.

If you're buying it pre-diluted it could take ages and may not work - they
dilute it to a ridiculous extent.

Indeed. But having sprayed myself accidentally I'm now a little
concerned about its alleged harmlessness so slightly reassured that the
solution was weak.

If the elder is large and has a significant trunk use the techniques
described here previously of hashing the bark to get the glyphosate past
the waterproof bark or drill holes into the trunk and top up with
concentrated glyphosate.

--
Windmill, Use t m i l l
J.R.R. Tolkien:- @ S c o t s h o m e . c o m
All that is gold does not glister / Not all who wander are lost