With each plant producing about half a kilogram of cannabis, a single room of plants could produce an income of about $100,000 a year, so growers were "making a lot of cash".
A bust in Featherston late last year resulted in the recovery of about 20 plants, which could produce an income of roughly $30,000 every three months, he said.
"Often people rent houses and if they are doing it in rentals, it can completely damage it, so landlords need to keep an eye on it and do regular inspections."
Indoor growers were often highly organised with lighting, extractor fans, water monitoring and timers to control lighting and watering systems.
"They can often be recognised by cannabis smells, often ventilated, coming from a house, garage or shed which has had any windows covered or curtains permanently drawn. Often there may be hoses running to the area and lighting on at night."
With good conditions, it could take as little as three months for a plant to mature, he said.
Detective Sergeant Barry Bysouth said outdoor growers went to great lengths to hide their plants, often trespassing on farmland or forestry blocks.
"They obviously do not want to be held accountable for their product and distance themselves from these activities ... they will centralise their plots close to water resources such as dams or creeks."
Rural burglaries also tended to increase in areas cannabis was grown, Mr Bysouth said.
"If they walk past a shed with a quad bike in it and the key is the vehicle - make no mistake, there is a real potential at some stage over the following weeks that the vehicle will be targeted along with anything else of value in the shed.
"Also, fences will be cut and gates left open to allow easy access. This in turn will cause stock to roam in areas where they will be lost, stolen or injured."
