K wrote:
Spores are light enough to be carried far more than 1m by the lightest
of breezes. Are you suggesting that if you can keep them from landing
within 1m of the ring, that is sufficient to prevent further growth?

The parents of my friend have a small urban garden. I suspect that's
why she used a small sheet. But I really don't know more. In such a
small garden and a minute lawn, I'd imagine she'd be more successful at
catching spores, which needs to land on the best location for them -
and since the space is small that was the best way to do it. I haven't
got hold of her yet. I know she's got a job with the Oldham and
Rochdale Groundwork now.

My neighbour has had a ring, or perhaps a crescent for about 3/4 years.
But she likes it very much. She also has lots of sculptures of fairies
dotted about in the garden. You won't find these in mine ;o)