Cannabis plants about a foot tall have been discovered growing in a Wellington City Council reserve.

A man planting native trees came across the plants in a reserve in Island Bay and the crop was seized by police on Monday night, but no arrests were made, Sergeant Andy Guy said.

Wellington City Council open spaces and parks manager Amber Bill said it was rare for cannabis plots to be found on city land.

The Island Bay plot contained only two plants, growing near a popular walking track off residential street Dargle Way. The area backs on to the City to Sea walkway that runs through Island Bay.

"We've got many reserves and community gardens around Wellington and they are all pretty well used," Bill said. "It doesn't surprise me that someone found them - it's not a great place to carry out that kind of illegal activity."

The seizure - as the prime cannabis growing season approaches - has exposed the practice by some growers of concealing their plants on public land in an effort to avoid being traced.

Authorities say clandestine cannabis plots have more traditionally been found in the rural areas and hills surrounding the Hutt Valley and wider Wellington region, rather than in the city.

Hutt City Council reserves assets manager Craig Cottrill said he had stumbled upon clandestine operations in the hills in the past.

There were often "telltale" signs that led to the plots - such as foot-worn tracks, leftover chicken wire and water containers, he said.

His most recent discovery was about 18 months ago at Te Whiti Park in Waiwhetu, Lower Hutt.

"They'd gone into the bush and found a little plot with some sunlight and even put a little fence around it to keep possums out."

The largest bush cannabis operation Cottrill had encountered was about eight years ago. Police were alerted to the three harvested plots of about five square metres apiece nestled in a pine tree clearing in the Akatarawa Forest, between Upper Hutt and the Kapiti Coast.

A spokesman for the Upper Hutt City Council said there had been an "issue" in the past in the Hutt Valley, but that had lessened in recent years.

Police said growers were mistaken if they thought they could not be linked with bush cannabis plots.

"I think there is a belief that removing it from their homes also removes the ability for us to identify them,"Inspector Mike Hill said. "But we have had success in the past where we have been able to forensically link offenders to plots."

Cultivation of cannabis, including sowing or planting, can result in a jail term of up to seven years or a $2000 fine.