In article , Janet
Baraclough. . writes
Lack of light will kill all
growth within a couple of months..

We use the method of light elimination on occasions. It works to a
limited degree in the sense that it inhibits growth, but we have not
found that it will eliminate grass in a couple of months. As a very
rough guide, the time that covers are left in place is the amount of
time which the ground will be weed free after they are removed.

I use black plastic sheet for that job. I put it in place on the area to
be cleared in autumn of one year, leave it there until spring of the
year after the next - around 18 months. That gives a year or so of
relative weed freedom, but sooner or later the ground will become
inhabited by unwanted growth unless good husbandry is practised.
--
Alan & Joan Gould - North Lincs.