It helps to declare a concentration when writing about Joni Mitchell. Trying to distill her influence on 20th-century music is a little like trying to trace Georgia O'Keeffe's impact on landscape painting, or Joan Didion's on the essay form. You can feel the legacy of her lyrics - her "moons and Junes and ferris wheels" - everywhere in confessional, contemporary pop, too, something analyzed at length by everyone from Pitchfork editors to the academics at Oxford University Press.

What hasn't always been given due critical attention, though, is Mitchell's complicated relationship with fashion, despite the fact that clothes - their meaning, their power - are central to her lyrics. (There's also the small detail of her having starred in both Hedi Slimane's spring/summer 2015 campaign for Yves Saint Laurent and a 1990 Herb Ritts shoot for Gap jeans, not to mention inspiring collections by designers as diverse as Emilio Pucci and Dries Van Noten.) While she's still largely perceived as the barefoot folk singer who stole away from the Saskatchewan prairies to become a liberal-minded Lady of the Canyon "wrapped in songs and gypsy shawls," Joni has always liked, for lack of a better phrase, nice things, and has demonstrated an eye for telling sartorial details since she first pressed Song to a Seagull. She may have decamped to a neolithic Cretan cave to write her seminal album Blue, but the songs she wrote there were about missing her "clean white linen" and "fancy French cologne" back home in California.

Mitchell's name first appeared in the pages of Vogue in the January 1969 issue, when journalist Mike Jhan delivered a state-of-the-union address about the world of pop music. "Now the dominant trend," he declared, "is to the real, the believable... Music that rings with a renewed spirit of honesty and simplicity, plus a feel for what is basic." Following the requisite grumbling about the impact of Bob Dylan going electric, Joni's self-titled debut gets a shout-out: "Her voice, firm, flexible, and joyful, rises and falls rapidly, striking a bass note then leaping tall octaves in a single bound." By the following issue, she had made it into the magazine's "People Are Talking About" pages, where a fascination with her appearance could already be felt: "Joni Mitchell, with lake-blue eyes, hair like poured Chablis, and a voice that echoes through invisible hills, who writes and sings with her guitar: at Carnegie Hall this month, at college concerts, on records. Torn between imagic nature and city grit, she wraps love around lyricism."

Before the year was out, Joni had become a poster girl for the Woodstock aesthetic - bishop-sleeved peasant blouses, and patchwork suede, macramé dresses and long, beaded necklaces. In truth, she never actually performed on Max Yasgur's now-mythic dairy farm, but she did write the festival's peace-love-and-paisley anthem: "By the time we got to Woodstock / We were half a million strong / And everywhere there was song and celebration / And I dreamed I saw the bombers / Riding shotgun in the sky / And they were turning into butterflies / Above our nation."

The image of Mitchell wearing what she would later call the "uniform of rock 'n' roll" ossified in our cultural consciousness, outlasting her own relationship with it by a good 50 years. In 1975, she wrote "The Boho Dance," skewering the bohemian affectation she had long been associated with and distancing herself from it: "Even on the scuffle / The cleaner's press was in my jeans / And any eye for detail / Caught a little lace along the seams." As she told Cameron Crowe in a much-referenced Rolling Stone interview in 1979, to be a flower child had become a "flat-out style," one she no longer related to, if, in fact, she ever did: "I remember showing up at a Carole King concert in Central Park in a pair of Yves Saint Laurent pants. And a good shirt. They were simple clothes, but they were of a good quality... I felt there were certain things that I liked, that were a part of me, that were outside the hippie guard."

That fact was abundantly clear when Architectural Digest visited Mitchell at her Bel Air home for its July 1976 issue, where a red antique silk kimono was draped over the stool of a Steinway, a giant albino tortoise shell hung on the living room wall, and much of the furniture consisted of sleek, modern designs by the Pace Collection's Perspex prophets Irving and Leon Rosen. The magazine described the exterior of the 1920s Spanish-style house as "wreathed by geraniums blooming in pots and Iceland poppies perched on stems that seem too fragile to hold their giant blossoms," while the interiors had been masterminded by Sally Sirken Lewis, a decorator with a Margaret Thatcher-esque haircut and a showroom on Melrose. She had allowed Joni to keep what she referred to as "my [Navajo] baskets and my Eskimo art," but painted the walls of her bedroom the color of "a forest at dusk," dragged 12-foot fishtail palms inside and crowded them around a fireplace, and installed Tiffany floor lamps to illuminate 18th-century cloisonné urns, all with her client's wholehearted approval. "A house," Mitchell concluded, "is important to me... I have good feelings here that go beyond the surface of things."

She still lived in the Bel Air house when Vogue paid a visit in April 1995, although by that point she had parted ways with her second husband and acquired three cats, "one of whom is named after the German philosopher she stumbled across during a particularly dark time in her life, Nietzsche," interviewer Charles Gandee reported. In the driveway stood a Mercedes roadster, while "a cobalt-blue mosaic pool" had been installed on the precipice of a ravine. By that time, any lingering traces of the Summer of Love had evaporated from her wardrobe, replaced by berets, Chanel 2.55s, and "predominantly Japanese clothes": "'I buy them for some occasion that never happens,' she confesses. 'I like some of Yohji Yamamoto's things, and I like the Victorian influence on Matsuda's work, but I'm addicted to Issey Miyake. Issey is an artist. When I travel I search out the Issey venues because Maxfield [the local purveyor of Miyake] doesn't buy him well.'"

Style is character, as Didion once wrote in an essay on O'Keeffe - and Joni's is somehow both eternal and ever-evolving.