‘Do you know what terpenes are?” says our glamorous host, pointing to four glass domes spotlit on a table, each containing mysterious lumps of black rock. The surrounding walls of this small room in Los Angeles are lined with mirrors, topped with neon arches that glow lilac, pink and purple, their reflections forming a trippy maze of arcades extending into infinity. It looks like some kind of cosmic chapel, an intergalactic shrine to precious meteorites, but this is Wyllow, one of the city’s new breed of boutique cannabis dispensaries, determined to elevate the humble herb to dizzying new heights.

Our hostess lifts one of the domes with a flourish and offers me a whiff. A rich, citrusy bouquet with piney undertones wafts forth, recalling lemon peel and woodland walks. Another dome’s scent is more smoky, a third musky and earthy with sweet notes of clove. It feels like I’m at a fancy wine-tasting, not a place to score weed.

“Terpenes are the volatile hydrocarbons that give plants their aroma,” she explains, sounding like the science bit of a shampoo commercial. “And they give different strains of cannabis their unique highs.” These rocks in front of us are not chunks of aged, vintage hash, as I had naively assumed, but lava stones scented with particular terpenes. Sniffing them is just the introduction to this curated cannabis shopping experience, the first step on my journey into the US’s mind-bending $30bn (£24.5bn) marijuana retail industry.

As America’s hippie capital of peace, love and good vibes, California has long had a relaxed relationship to pot. It was the