Where do recreational drugs in The Netherlands come from?

Where do the Dutch get all their recreational drugs from? I’m sure there are pots of, um, pot growing in households, but are there large (legal) greenhouses for marijuana beside those for tulips? Is it a commerical venture?

Can’t remember where, but I read that an application for a large greenhouse for doing this was turned down, it seemed that it wasn’t just a simple denial of planning permission on the grounds of looks or drainage or the like. No-one I know who has gone there knows anything about this either, just that it was freely available.

Most pot is grown illegally at homes or at farms. I know that where I used to live (Valkenburg, way in the South) each winter a few potfarms get raided. The way they find them is because the p-lants require a lot of heat that if we do get snowfall you an easily pick out the patches where there is no snow.

I believe the city of Maastricht (not the poster) tried to start a commercial legal potfarm to control the quality/quantity of pot on the market but the government stepped in and said no.

Rotterdam is one of the busiest ports in the world.