Medicinal cannabis growers at the country's largest farm of its kind say they have found success after switching production from tomato plants to the crop.

Eastern Daily Press: The glasshouse grows three rounds of crop per year. Picture: ArchantThe glasshouse grows three rounds of crop per year. Picture: Archant (Image: Archant)

British Sugar began growing the crop to be used in cannabis-based medicines for pharmaceutical company GW Pharmaceuticals in 2016, to be used in drugs to help patients diagnosed with a rare form of epilepsy.

The 18-hectare glasshouse at the Wissington factory houses a non-psychoactive variety of the plant, which can be grown successfully thanks to recycled carbon dioxide wasted in British Sugar's sugar beet operations, as well as a number of other factors.

MORE: Could windfarm projects cause Norfolk mussel population to die of stress?Colm McKay, agriculture director for British Sugar, said: "Any grower, be it a farmer or horticulturalist, is always reviewing what crops they should grow.

Eastern Daily Press: Hot water is pumped through hundreds of miles of pipework to maintain a warm environment. Picture: ArchantHot water is pumped through hundreds of miles of pipework to maintain a warm environment. Picture: Archant (Image: Archant)

"We went through a review process to see what we could potentially grow and in conversations with GW Pharma it became clear that we could very successfully grow the crop for them."

Having previously produced tomatoes, the glasshouse had to be reconfigured to include 240 miles of piping carrying hot water for heating the plants, as well as the installation of 19,000 LED lightbulbs.

The team of 36 based at the site managed to begin growing the crop from cuttings within seven weeks, and now take delivery of 800,000 plant pots every cycle.

Mr McKay said: "Our horticulturalists can grow the plant to the high level of specification that is required of this crop. The crop is highly regulated because of the quality of ingredient you need to produce for it to be used in the pharmaceutical industry."

Eastern Daily Press: Hundreds of thousands of plants are grown in the Norfolk glasshouse. Picture: ArchantHundreds of thousands of plants are grown in the Norfolk glasshouse. Picture: Archant (Image: Archant)

The specific ingredient needed from the plants is CBD, the highest yield of which can be found in the crop's flowers.

The flowering cycle of the plants can be controlled by light levels, and have a lifespan of around 18 weeks before they are dried down and exported.

"We've had a lot of interaction with the local community, and there were questions asked by the local community as you can imagine, but often we invite them to visit and when they come here and are able to see and hear what it's being grown for it breaks down a lot of those barriers," Mr McKay said.

Eastern Daily Press: Inside the 18 hectare glasshouse at British Sugar's Wissington cannabis farm. Picture: ArchantInside the 18 hectare glasshouse at British Sugar's Wissington cannabis farm. Picture: Archant (Image: Archant)

Eastern Daily Press: Cannabis flowers contain the most CBD oil. Picture: ArchantCannabis flowers contain the most CBD oil. Picture: Archant (Image: Archant)

Eastern Daily Press: Colm McKay, agriculture director at British Sugar. Picture: ArchantColm McKay, agriculture director at British Sugar. Picture: Archant (Image: Archant)

Eastern Daily Press: Carbon dioxide is stored in containers beneath the plants to aid their growth. Picture: ArchantCarbon dioxide is stored in containers beneath the plants to aid their growth. Picture: Archant (Image: Archant)

Eastern Daily Press: The cannabis plants take 18 weeks to fully mature. Picture: ArchantThe cannabis plants take 18 weeks to fully mature. Picture: Archant (Image: Archant)