The wine was pale garnet, with notes of smoke and blackberry giving way to a lingering, slightly tart, finish. One sip sent my head spinning.

But then this particular vintage was more potent than your usual Californian red. The grenache, from Know Label wines in Arroyo Grande on the central coast, is infused with cannabis flowers.

Plastic cups of wine were passed around along with joints as our party bus chugged over the Golden Gate bridge. Tupac’s California Love oozed from the speakers into an atmosphere as foggy as a San Francisco morning.

It was the first tour combining wine and weed in California, and the brainchild of Heidi Keyes and Michael Eymer, who run Colorado-based Cannabis Tours. This tour will officially launch in early 2018, when recreational cannabis use becomes legal in many areas of the state. Until then, a medical marijuana card is needed. But the new law means even international visitors will be able to buy cannabis, opening up a new world of tourism possibilities.

“There are so many other ways to use cannabis than to smoke it,” said Keyes, marijuana-leaf earrings jangling. “I think wine and weed can be a great combination in the right quantities.”

High-end edible cannabis snacks at the Curious Cannabis Salon, San Francisco. Photograph: Karen Wang

Others are following suit. Jordan Lichman, co-founder of Sea of Green Tours, is planning winemaker dinners in Sonoma, with “California cuisine, top wines and cannabis brands”.

Lisa Rogovin, who founded Edible Excursions food tours, has just launched a Curious Cannabis Salon, showcasing various high-end edible cannabis products in San Francisco.

Our tour began at the Oakland Cannabis Creative with a “mocktail” demonstration. Looking like a hipster let loose in a laboratory, bow-tied Andrew Mieure expertly sprinkled and pipetted various doses and strains into spiced apple drinks. His Denver-based company, Top Shelf Budtending, caters for private events, promoting “classy cannabis” and responsible use.

“You should ideally smoke before you drink,” said Mieure. He was on hand throughout the trip with tinctures and sniffing oils “to bring people back” if they got too high. “Alcohol acts as a muscle relaxant, so the cannabis absorbs quicker into your bloodstream.”

The tour dropped in at the Betty Project, a San Francisco grow facility. Clutching glasses of sparkling (non-infused) wine, we peeped at plants bathing in chartreuse-green lights. Aromas of sage, eucalyptus and lemon verbena wafted from the drying room.

Cannabis accompnaies the fine wines and dinner on a Sea of Green Tour.

Our last stop was Donkey & Goat Winery in Berkeley, north of San Francisco. They don’t serve “green” wine – as cannabis-infused varieties are known – only red, white and orange.

Gloria, on the tour with her husband, sipped contentedly from a glass of pinot gris and nibbled on a breadstick: “Wine, cheese and weed. How can you complain?”

Visitors shouldn’t get the impression that from 1 January cannabis sales will be legal throughout the state: many city authorities have not yet agreed to issue licences, and Fresno and various counties have banned sales.

As we got back on the bus, Keyes surveyed the sea of serene faces. Some slumped in their seats, half dozing. Others mainlined Doritos or stared, button-eyed, as San Francisco’s skyline soared past the windows.

“If this was just a drinking tour, people would be wasted and throwing up or fighting by now,” said Keyes. Eyes shining, she added: “I mean, I love wine – and I love weed. It’s perfect.”

• The Wine and Weed tour costs $99pp, cannabistours.com