A 35-year-old disaster consultant quit his job in December after making $515,000 so far in trading marijuana stocks. Thanks to the legalisation of cannabis in some states, trading in the once-prohibited drug - both in real leaf and on paper - is becoming a growing subsector in international stock trading.

Outside the U.S., on Friday, Tweed Marijuana became the first Canadian provider of medical marijuana to list on the country's stock exchange, opening at $4.60 per share and trading more than 2million shares in the first 15 minutes. When it closed at $2.59, Tweed shares were the most actively traded shares on the TSX Venture with almost 10 million exchanging hands that day.

The American weed trader, who runs the #WolfPack Twitter community, uses an online alias Wolf of Weed Street, a play on the movie character Jordan Belfort - portrayed by Hollywood actor Leonardo di Caprio. He provides advice on how to earn from trading weed stocks.

He suggest that interested traders look into the index that tracks the performance of marijuana industry stocks, which is limited to firms with a minimum market capitalisation of $1 million. In February, the index soared 125 per cent, although it has since declined significantly.

Other shares to look out for are not necessarily limited to cannabis growers but also companies that provide marijuana-related products such as vapour inhalers to weed-vending machines. Don't overlook companies that provide security to legal marijuana plantations and warehouses.

Todd Harrison, a former Morgan Stanley banker and founder of the investment portal Minyanville, said, quoted by BBC, "It's the single best investment idea of the next decade. He compared the growth of marijuana stocks today to the dotcom era in the late 1990s, jokingly referring to it as the dot bong era.

However, Mr Harrison noted the hesitancy of some stable and legit firms to trade in cannabis stocks over fears of facing drug racketeering charges in the future.

Another pot stock expert, professional investor Alan Brochstein, who opened the 420 Investor service on Marketfry on Jan 1, the day legal recreational marijuana sales began in Colorado, has organised the Cannabis Investor Conference, also known as WeedStock, in Denver on June 29-July 1.

The Wolf of Weed Street is actually a member of the 420 Investor service, Mr Brochstein disclosed.