Thousands of cannabis plants likely to be worth millions of dollars have been destroyed.

More than 10,000 cannabis plants were destroyed in summer raids across some of New Zealand's most fecund dope-growing regions.

In news likely to depress consumers already complaining of cannabis shortages, 4000 plants were wiped out and 43 people prosecuted or warned for cultivating the plant in Hawke's Bay.

Thousands more plants were destroyed in Gisborne and the East Coast.

MARTIN DE RUYTER/ FAIRFAX NZ Police and air force staff with cannabis found during a Marlborough aerial operation last year. Even more plants have now been seized in the North Island.

Eastern district police said the operation spanned the cannabis-growing high season from early summer until March. It targeted dealers, growers and suppliers.

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Information on the volume and value of seized cannabis was not immediately available.

SUPPLIED Cannabis is New Zealand's most popular illegal drug, and conditions for growing it are perfect on the East Coast.

However, multiple media, anecdotal and social media reports over the past year have suggested a chronic cannabis shortage was hitting local consumers.

Based on price information from online sources, and a judge's recent ruling, the Eastern district raids could have netted police pot with a street value as high as $12million.

A Wellington judge in January said seized plants assessed in his cannabis-growing case case were worth $1200 each.

A police spokeswoman said outdoor and indoor cannabis growing operations were found during the operation. Nine firearms were also seized.

People arrested were charged with offences including cannabis cultivation, possession of the weed for supply, and illegal possession of firearms.

"We are constantly monitoring the activities of drug dealers who should in no way feel as if the pressure is off them now," Detective Senior Sergeant Brent Greville said.

The Drug Foundation said cannabis was the most widely used illicit drug in New Zealand, and 42 per cent of all New Zealanders older than 15 had tried it.

Hawke's Bay and the nearby East Coast region contain many areas of the fertile Orthic Recent soil type, abundant sunshine and warm weather ideal for cannabis cultivation.

The Weed Blog said plants could yield 150 grams of marijuana under "perfect" outdoor growing conditions.