The four-month drug taskforce operation targeted a sophisticated cannabis trafficking network, with most of the houses searched containing hydroponic commercial cannabis crops, a police spokesman said.

More than $250,000 in cash was also seized. Thirteen people were arrested with eight appearing at the Melbourne Magistrates Court on Friday.

Detective Inspector Doug Fryer of the taskforce said he believed the operation would have a significant impact on the illegal cannabis trade.

"This successful operation has removed in excess of half a tonne of cannabis from making it to the streets."