"Brian Watson" wrote in message
...
harbour mould spores :0)

And bare concrete wouldn't?
No because it will dry out whereas carpet tiles if inside a greehouse might
stay damp for ages. Plus you can chuck a bucket of bleachy water down on a
concrete floor or jeyes fluid so killing mould spores and other nasty things
like insect grubs, larvae and eggs.

A hard (ie, not earth) greenhouse floor should remain dry unless watering
the plants on benches or in the side beds splashes over.

Therefore I can't see any problem with carpet tiles which have the benefit
over one piece of carpet of leaving a clean non-fraying, edge when cut.