The figure has been revealed by West Midlands Police who say they are continuing to "strike" against organised crime gangs believed to be behind most of the cannabis factories.
One of these farms was in Slaney Road, Walsall, where officers found more than 6,000 plants crammed into 40 rooms in one of the biggest finds in the force's history.
Detective Chief Inspector Nick Dale, from the force's Serious Organised Crime and Exploitation team, said: "We’re not talking about some recreational drug use here…this is top-level organised criminality, linked to exploitation and violence.
"The cannabis factories can be in industrial units or disused factories but often we find them in residential streets surrounded by family homes or even near schools. They are a magnet for anti-social behaviour and crime.
"Increasingly people are getting fed up with being blighted by these drug factories and are calling us with information. That’s helping us uncover more and more illegal premises and damaging the revenue making streams for crime gangs."
Police said many of the industrial-size cannabis production set-ups are linked to organised crime gangs who are "making big money on the back of others' suffering" as they pledged to stamp out the crime.
Officers said they have found people who have been trafficked illegally to tend the crop, living in squalid conditions in the drugs dens, while children or vulnerable people are used to deal drugs or move them across the country.
They are exposed to risk of serious harm, notably from rival gangs intent on stealing the drugs or disrupting the "business".
Armed robberies are common at cannabis farms and often leave people seriously injured or dead, such as in the Brierley Hill raid where two people were killed with a crossbow.
The force also issued a warning about the danger of bypassing power supplies, a common tactic for supplying the electricity needed at cannabis factories, where dangerous wiring can be a serious fire hazard and lead to the set-up going up in flames.
Anyone who suspects a property is being used to deal or produce drugs is asked to to contact police or Crimestoppers.