What is the purpose of the plastic covering on GRODAN?

The white plastic that surrounds the blocks helps keep the plants separate, prevents algae growth on the side of the block, keeps diseases from spreading, and prevents light damage to roots that may extend out of the block. So keep the wrapping around the blocks unless you plan to pot up the plant into a loose medium such as clay pellets or GRO-WOOL™.

However, there is also a clear shrink-wrapping on the strips of blocks and the sheets of propagation plugs. The wrapping is there for ease of handling in the retail store. This shrink-wrapping should be removed prior to use.