Thousands of Australians donned a red poppy to commemorate Remembrance Day, but thefts of parts of a potentially deadly variety are creeping up in Tasmania.

To most the poppy is a pretty garden flower, but in Tasmania opium poppies that are refined into medicines such as morphine and codeine are a major agricultural crop, with the island state supplying half the global stocks.

It's an eye-catching and lucrative crop, but tightly controlled, because the plant's capsules can be deadly if ingested.

Stolen poppy capsules have caused the death of several people in the last decade, most recently a Hobart teenager who overdosed in 2012 after brewing a tea of poppy heads.

The Tasmanian Justice Department's annual report reveals capsule thefts are creeping up.

A total of 516 capsules were stolen in 2015-16, up from 331 the year before, although far below the 3,923 capsules stolen in 2013-14.

Chief executive of Poppy Growers Tasmania, Keith Rice, said some losses classified as thefts could be attributed to snap-happy tourists.

Poppies ready for harvest in Tasmania. ( Audience submitted )

"It's the curiosity. People stop, take photos of them, take some of the flowers," he said.

"They enter into the paddock to sit down amongst the flowers and trample them down, and sometimes these are counted as thefts too.

"It would be my view that it's not local people. It would be interstate and overseas visitors, they're absolutely taken by the flower, the kaledioscope of the landscape and they go in to take a closer picture."

A sign warns people not to pick potentially deadly opium poppies growing on Tasmania's north coast. ( ABC News: Libby Price )

Roadworks likely to prompt regrowths

The Poppy Advisory and Control Board strictly regulates poppy crops, and each field needs to be re-licensed to grow every season.

A total of 653 licenses were issued in 2015-16.

More poppy regrowth was detected in unlicensed areas, from 38 instances the previous year to 62.

Mr Rice said the major road redevelopment on the Midlands Highway was likely to disturb poppy seeds in the soil.

"Whenever you're going through agricultural land that's been used for poppies and new roads are going through there, there would be a high expectation of poppy regrowth coming up," he said.

He said poppy regrowth has been an issue many years ago when substantial work was happening around the Bass Highway and the Devonport overpass.

Tourists are being blamed for some poppy thefts. ( ABC News: Libby Price )

Demand dropping for Tasmanian poppies

Just 13,224 hectares were harvested in Tasmania last financial year, down from 20,631 hectares the year before.

A global oversupply is biting, with major alkoloid companies slashing orders for Tasmanian crops earlier this year.

The industry is expecting an even lower harvest this year.

"We were hoping this year that it would increase a little, but it fell from [a contracted] 14,000 hectares last year to 11,000 hectares [this year]," he said.

Mr Rice said with poorer weather conditions this year, only about 7,500 to 8,000 hectares had been prepared.