Glyphosate is a waste of time for killing brambles. It will make them look
poorly for a few weeks then they continue growing, slightly deformed. Even
with repeat treatments it does not kill them. I know because I tried on 1/2
acre brambles.

I also tried the pick and dig method, but if any root is left in (which it
will be) they will just shoot again. The problem is the underground runners.
Very difficult to get rid of.

In the end I used a specific bramble weedkiller - sorry I can't tell you the
brand name but it was made by "Bayer". I can give you the composition: 20g/l
fluroxypyr (ester-1-methylheptyl) and 60 g/l triclopyr (a form of
triethylamine). So look out for that on the box. Hope this helps.

Norman Digger.