Two real estate franchise owners have been charged after police uncovered thousands of cannabis plants at dozens of residential properties across Melbourne's north and west.

Chris Lio and Con Constantinou, owners of Barry Plant Real Estate's Epping franchise, are among eight men arrested in connection with a large quantity of drugs.

Barry Plant chief executive Mike McCarthy said he was shocked to learn the pair allegedly used 25 properties managed by their branch to hydroponically grow some 3000 cannabis plants.

"Nothing like this has occurred in our history," Mr McCarthy said in a statement on Saturday.

"These are serious charges and everyone in our group, from head office right through our 82 franchises, is shocked and dismayed."

Mr McCarthy said the Epping branch was independently owned and operated.