COPS AND CROPS: RNZAF personnel accompanied by constables from the Nelson Bays Police area recover cannabis in the Tapawera area.

This year's dry summer has been hard on cannabis plants in the Nelson region.

Police say untended plants recovered during its annual cannabis recovery operation were in "woeful" condition.

Detective Sergeant Brett Greer said police had finished its operation in Nelson and Marlborough looking for mature plants which this year was called Operation Ruth. The recovery operation is run in conjunction with the New Zealand Air Force.

Mr Greer said this year about 2000 plants were found by police in Nelson Bays, Marlborough area. A total of 5000 plants were found in the Tasman Police district which includes the West Coast.

One person would be arrested and it was likely further arrests would be made as police worked through the information it had.

Mr Greer said the number of plants seized was down on previous years.

He said the weather had played a part, as while plants had been maintained were of good quality others left to fend for themselves in remote areas in the dry weather were "woeful".

"Some of those plants are terrible, but there have been some carefully looked after."

Police had also treated the operation differently this year and had worked on trying to disrupt the cultivation by executing search warrants and finding plants before they got into the ground.

He believed a couple of early success by police in preventing plants from being planted had also impacted on the number of plants found.

Police were not finding large plots of cannabis any more as growers favoured smaller plots.

Mr Greer said cannabis from the Nelson region made its away around New Zealand.

Aotearoa Legalise Cannabis Operation media spokesman Steven Wilkinson said the weather did not have an effect on cannabis, as it needed a sixth of the water to grow than cotton did.

He said the annual cannabis operation was an expensive PR operation by police and a waste of taxpayer money.

It would actually be more cost effective for police to buy the cannabis on the black market for the amount that they were recovering.

He said the real reason police were not recovering much cannabis was that there were a lot more indoor growing operations.

The operation probably only caught about 10 to 20 per cent of cannabis grown in the region, and this would become more apparent in a couple of months, he said.

Rather than flying around in helicopters like GI Joes it would be better for police to put resources into protecting youth and others at risk, he said. The best way of doing that was through education.