I don't see any problem with using the stones. I have limestone in my greenhouse. When it gets wet it helps to humidify the greenhouse.

Ok, that's one good reason to use them. Thanks!

I was upset because in our climate, the plastic sheet traps the hot air from the heated granite chips; it's just like an oven.

Lyndi, we use blue rock gravel because it's durable, clean (compared to soil) and allows for drainage in areas that are being watered constantly. I can't really think of another way to do it, unless it's just covering the soil with weed mat. We've done that in some areas, particularly where the ground is not level, but it tends to get muddy anywhere there's a depression. Also you can trip over it if the edges are not nailed down properly and it wears and snags more if it's exposed. The combination of the two (mat covered with a layer of gravel) seems to work the best for both weed control and drainage.