Image caption Glass jars at a marijuana shop in Colorado show off the diversity of varieties available

Earlier this year, Colorado made history by becoming the first US state to sell marijuana legally. Since then, the number of businesses offering a wide range of pot experiences has exploded, and some foresee a "Green Rush".

Marjorie is accompanying her husband on a business trip to Denver. She has a day free.

"If you're in France, you go on a wine tour, if you're in Colorado these days, you go on a pot tour," says Marjorie, 66.

Some cannabis tour companies cater for buses of bachelor parties. But Marjorie went for "Green Tripz" - a VIP tour in a "pot-friendly" limousine.

"This is a smoking vehicle, just don't blow it at me, that's rule number one," says Mike, Marjorie's driver and guide.

"I can't start smoking straight away because I'll be too loaded," says Marjorie.

Image caption Brett Schneider is one of many young entrepreneurs hoping to benefit from the legal pot industry

At the beginning of the year, Colorado became the first state to legalise cannabis, after voters approved the change in 2012.

The result is not only the birth of new marijuana tour companies, but also a startling burgeoning of the cannabis industry as a whole.

Business graduates and young entrepreneurs such as Brett Schneider of the MaryJane Group have flooded into the state looking to get in on the action.

"I think the sky is the limit for the industry," he says.

"One of the things I've learned is that the real way to go about it is to be safe and responsible. If you hold those as your two brand attributes that you really stand true to, you can change the perception of cannabis."

First stop on Marjorie's tour is a dispensary that grows marijuana, one of the more than 250 cannabis retail outlets established in the city of Denver in just six months.

She is fascinated to hear about the different types of cannabis on offer and the different effects they could have on her state of mind.

Image caption Critics say the industry needs to be regulated

Among her purchases at the first stop are the products that have become an unexpectedly huge hit in Colorado - cannabis "edibles". Edibles include the classic cannabis brownie but much more besides - marijuana candies, drinks and chocolate bars.

"I got a pre-rolled joint and a little tin of chocolates," Marjorie proudly announces. She takes a quick puff in the limo on the way to our next stop, which Mike describes as a "big surprise".

This extraordinary proliferation of cannabis outlets - and the new varieties of them - has angered opponents of marijuana legalisation.

"We are seeing in front of our eyes the creation of the next tobacco industry," says Kevin Sabet, one of the national founders of a group called Smart Approaches to Marijuana.

"This idea of control and regulation is a mirage. The industry is controlling what is happening," he says.

Medical emergencies

In particular, he wants edibles banned immediately, arguing they are relatively untested and contain high concentrations of the active ingredients of cannabis.

"The industry needs to take all these edibles off the shelves," Mr Sabet says. "The idea that you have to cut a chocolate bar in to 16 pieces in order for it to be safe is absurd. No one does that,"

Since legalisation, more people are seeking help in hospital emergency departments for acute cannabis-related illness, says Dr Christopher Caldwell, Director of Emergency Medicine at Denver Health.

"One trend we are seeing is much, much higher concentrations of marijuana in patients that we were never seeing before," he says.

He says most incidents come from overconsumption of marijuana edibles, though most patients recover completely with time.

"The other thing that we are seeing is folks' willingness to take just about anything somebody gives them with the introduction of, 'This will get you high,'" says Dr Caldwell.

Image caption The intense "shot" marijuana experience proved too much for Marjorie

As we pull up to "Dab Kingdom", a little house decorated on the outside to look like a kindergarten, we witness just what an effect that can have.

"'Dabs' are concentrated trichomes, the psychoactive part of the marijuana, so that's what's going to get you high," says the barman, showing us a little block of resin.

"It's kind of like taking marijuana's version of a shot," he says, to Marjorie's delight, though she had no idea what she was getting into.

He lights a blowtorch, places a small amount of the resin on a metal nail, and blasts it.

Marjorie inhales the vapours through a glass tube and holds it in. The effects are almost immediate.

She becomes uncommunicative. First giggly, and then quiet and apparently very queasy, she aborts her tour saying she needs to lie down in the dark, missing out on a trip to the bong and water pipe shop.

As other states consider following Colorado's example, it's clear that when it comes to weed, there are going to have to be limits.