Grodan Launches Vermiculite-Free Plantop NG2.0 Funnel Plug. Global leader in stone wool growing media solutions Grodan announces the launch of a new Funnel Plug. Unlike other stone wool plugs, the patented Plantop NG2.0 Funnel Plug does not require the propagator to add a layer of vermiculite after seeding. That means excellent results and a cleaner work environment, and is particularly important because vermiculite is becoming increasingly difficult to source.