Undercover police officers wore wires and posed as customers wanting to buy cannabis growing equipment, as part of their investigation into the Switched on Gardener chain.
The recorded conversations will form part of the Crown case against five men and two companies who deny belonging to an organised criminal group and supplying equipment to grow cannabis.
Michael Maurice Quinlan - the owner of Switched on Gardner - is alleged to have been the head of the operation that the Crown describes as a "one-stop shop'' for cannabis growing equipment.
Crown prosecutor Gareth Kayes told the Auckland District Court today that Quinlan's 16 stores across the country sold equipment for hydroponic cannabis growing; including lamps, extractor fans, and electronic timers.
He said the shops even sold a "how-to'' grow cannabis guide as well as marijuana pipes which were labelled as "vases''.
Brands of fertiliser had cannabis-inspired names, such as "budzilla'' and "head-master''.
Quinlan's two companies, Stoneware 91 Ltd and Hydroponics Wholesalers, are also on trial.
Also in the dock was general manager Peter John Bennett, business development manager Ricky Cochrane, distribution manager Andrew Barry Mai and the South Island manager Paul Kenneth Barlow.
Mr Kayes said the police sent in undercover officers wearing recording devices. They talked to staff and some of the managers of the company.
He said three of the undercover officers pretended to be interested in setting up a shop called the "Green Room'' which planned to source equipment from Quinlan's Hydroponic Wholesalers company and operate out of Greymouth.
Mr Kayes said the men received training in Switched on Gardner shops and talked to Cochrane and Bennett.
"The Crown says that when you listen to the conversation it is going to be very clear to you that the men knew what the equipment and material was going to be used for.''
He said more than 25 staff members have already been convicted of supplying cannabis equipment, including the area manager and the operations manager of the company.
Paul Davison QC is representing Quinlan, Bennett and the two companies Stoneware 91 Ltd and Hydroponics Wholesalers.
He said the undercover police officers were insistent in their conversations, but staff were under no illusions about what to do when people started speaking about growing cannabis. "They were not to talk''.
He said if conversations about drugs did take place, that was a reflection on staff and not the management.
Mr Davison said while Quinlan and Bennett were supporters of legalising cannabis, those beliefs stopped at the front door.
"The way the company operated did not permit or allow any illegal activity. There was far too much to lose.''
Mai's lawyer High Leabourn said his client worked on the factory floor and filled orders for shops.
"He took part in no organised criminal group because there wasn't one.''
The trial, before a jury of eight women and four men, has been set down for eight weeks.