Hemp, one of the planet's most misunderstood plants, is finally shedding its undeserved bad rap.

Hemp is also known as cannabis, and cannabis is generally and mistakenly regarded as a narcotic.

Since the rise of drug culture decades ago this fast-growing, fibrous plant has been widely vilified, shunned and prohibited, but that is now changing.

High time for change

There are some 2,000 cannabis varieties, and most of them have minimal tetrahydrocannabinol (THC) — that's the crystalline compound and main psychoactive ingredient.

In other words, it is what helps get you high.

Australia's nascent hemp industry is also getting a buzz, but not from THC.

It is excited by legislation passed in most Australian states in 2017 and enacted last year that allows the cultivation and human consumption of hemp seed.

Since then, every Australian state and territory has seen trial plots grown, harvested and evaluated.

Although it has almost no THC, industrial hemp closely resembles its more narcotic relation. ( ABC: Tim Lee )

Hemp stalk is an ancient building material, while hemp seed is a nutritious food for humans and animals.

Retired television executive David Brian belongs to a growing global band that is spearheading a cannabis comeback.

He said it is a shame there has been so much misinformation.

"Even my family have said, 'oh that's marijuana, isn't it?'" he said.

Building up an industry

While the legalisation of medicinal marijuana has made headlines, Mr Brian believes hemp's greater potential lies in the building industry.

He is closely evaluating trials of industrial hemp and searching for dual-purpose varieties that have strong stalks as well as seeds suitable for human consumption.

He has helped build houses from a material called hempcrete in the ranges east of Melbourne, and is so taken with its potential that he wants to spend several million dollars to build a commercial hemp processing plant.

Hempcrete is made from the inner part of the hemp stalk, the hurd, mixed with lime and water.

David Brian applies a blowtorch to a hempcrete panel. ( ABC: Tim Lee )

Once dried it resembles conventional mortar, but its properties are rather startling. To begin with, it is almost entirely non-combustible.

Mr Brian happily gives demonstrations where he applies a gas flame to a hempcrete panel.

Even after ten minutes of intense heat, it fails to combust.

That heat-resistant quality is a major reason Corinna Willowson chose to build a hempcrete house.

She lives in a bushfire-prone zone in the heavily-forested region east of Melbourne.

"It just seemed like this is an amazing product," she said.

"Actually building with it and being in the cottage now, it's everything that I had hoped for and more."

Proponents say hemp buildings have a very low environmental footprint, great insulative properties and amazing fire resistance.

Architect Alvyn Williams' firm specialises in sustainable building, and he sees hemp fibre as a replacement for timber.

"There's a whole range of products that can be made out of hemp," he said.

Hemp can be used in a range of products, from clothing and food to building materials. ( ABC: Tim Lee )

"It's like using grass, which hemp is, effectively.

"It's an annual crop. It's a much stronger, better way forward."

Nationally, there are less than two dozen hempcrete houses, but the legalisation of hemp growing across Australia has thrown the door wide open.

Growing recognition

Hemp seed is also extremely valuable, and local product, increasingly sought after by the health food sector, is replacing imports.

It might be predominantly grown for its seed, but utilising the harvested stalks will help the crop's viability.

Mr Brian is hoping to build his hemp stalk processing plant in northern Victoria, and anticipates there will soon be large plantings of industrial hemp.

Mitch Costin and his business partners from Australian Primary Hemp have focused on the food sector.

Mitch Costin of Australian Primary Hemp inspects newly crushed hemp seed destined for the health food market. ( ABC: Tim Lee )

Their factory processes hemp seed at Geelong for a range of health foods.

"I think the legalisation has made a massive change in it," Mr Costin said.

"Around the globe, it's starting to become a more recognised health food and not seen with the negative aspects that other people associate with its brother plants."

Cathy and David Briant planted six varieties in a trial at Neerim South, east of Melbourne, and held a public field day to help promote this emerging crop.

"Industrial hemp is not marijuana," said Ms Briant. "It's really healthy, with omega-3, 6, and 9."

As proof, the Briants' trial varieties were tested for THC.

They registered less than one percent.

Cathy and Andrew Briant held a field day at their farm to share their knowledge. ( ABC: Tim Lee )

Watch this story on ABC TV's Landline this Sunday at 12:30pm or on iview.