The message
from Sacha contains these words:

Personally, it would remind me of municipal cemeteries where all-too-many
graves are covered in glass.
One source of clear glass could be the people who replace windscreens. I'd
hate to do the weeding in that garden, though - ouch!

Pooter's been dead for a while and the backup wouldn't yield up COM2, so
I might have missed - well, I have missed a lot of posts.

Most of this glass 'mulch' has been melted into pebbles, so doesn't have
the sharp edges everyone (I've seen) attributes to them.

--
Rusty Hinge