The message
from Janet Tweedy contains these words:

I even though about putting that chemical on the ground that stops ALL
germination for six months, as the area is useless for growing on in,
case I break any more roots of the weed. So I have a 14 foot square bed
that I haven't grown anything in save blackberries for about ten years
...............

Simozine or something of similar spelling. My advice would be not to use it.

I had a smallholding and because I couldn't use all my 17½ acres at
first, I let some to a neighbouring dairy farmer, who put it down to
maize, treating the ground with Simozine (Sp?) to kill off the
competition - maize being for some reason, unaffected by it.

Two years after the last maize crop, I ploughed and harrowed the six
acre field and sowed spring barley, very little of which came up.

I had to replough and re-harrow twice before I could do anything at all,
and the ley of mixed grasses and clover I put down eventually didn't do
well at all for a couple of years.

--
Rusty Hinge
horrid·squeak&zetnet·co·uk
http://www.users.zetnet.co.uk/hi-fi/tqt.htm