Dutch company Bejo Seeds' sole Australian operations are in Tasmania.

In 1998, it bought southern farmer Clive Ockenden's Coal River valley operation - which grows brassica seeds such as cauliflower, broccoli and cabbage - which began in 1990 as a joint venture with Roberts Limited.

Now the company is expanding into Northern Tasmania with a $5 million seed production and drying facility at Cressy to be built by October, Mr Ockenden says.

"We wanted to grow more carrots and beets, and the North suits those crops because there's more irrigation water available, bigger areas of cropping land, and more experienced farmers," he said.

Mr Ockenden said the search started two years ago for a suitable small farm in the North, before the company settled on a 10ha property just south of Cressy.

As well as starting small-scale seed production trials onsite, construction has begun on an 86m by 30m drying, cleaning and export shed.

The building phase is due for completion in early October before a three-month fit out.

Once finished, the facility will produce up to 100 tonnes of carrot seed and up to 150 tonnes of beetroot seeds each season for export to the Bejo parent company in Holland, before being sold around the world.

Mr Ockenden said drier conditions in Northern Tasmania associated with changing weather patterns meant "absolutely perfect" growing conditions for vegetable seeds.

"If our climate is getting drier, that's great," he said.

"Our run in to summer has been perfect."

Bejo's agronomist Freyr Colvin is responsible for managing the company's Northern crops, which are grown from Tunbridge to Hagley, largely in the Longford and Cressy areas.

"I manage the crops on a day-to-day basis, (looking out for) any diseases, insect damage, sowing, and harvesting," she said.

Miss Colvin said the new facility at Cressy was a significant investment in the Tasmanian operation.

"It's going to give (farmers) some security for the crops that they are growing," she said.

"It says that (Bejo) are going to be here for a long time, so they can grow future crops with us."

Miss Colvin said installing their own cleaning and drying machines, rather than contracting out this step of the process, would tighten the turnaround time for growing the seeds.

"Carrots are a 14-month crop," she said.

"They're sown on the last day of February and harvested in April the following year, so they're one of the longest crops to grow, and they're exported in the August or September after they've been cleaned.

"Beetroots are planted in the first couple of weeks of March and harvested the following March, then exported around the same time as the carrots."