Police found the drugs during a search at Windsor Bungalows in Newry yesterday.
The plants have been seized, along with equipment used in the cultivation of cannabis and other drugs paraphernalia.
Detective Inspector Keith Gawley said: “Officers searched this house after a member of the public reported concerns about an unusual smell emanating from the property.
“The discovery of this haul has taken a substantial amount of drugs off local streets and demonstrates that when people report their concerns to us, they are actively helping us stamp out the scourge of drugs in Newry.
“I would encourage anyone with concerns about drug cultivation, dealing or supply in their community to please get in touch with us on the 101 non-emergency number.
“You can also report via Crimestoppers on 0800 555 111.”