It would be fair to refer to Mary Gauthier as a late bloomer. After all, the Nashville-based roots-rock artist began writing songs at the ripe old age of 35. Gauthier, who comes to the Somerville Theatre this Friday, has been making up for lost time ever since.

"I’m just getting started," she says a little mischievously over the phone from her Nashville home, a few days before embarking on the New England leg of her current tour in support of 2002’s Filth & Fire (Signature). The Somerville show will be a homecoming of sorts for the now 41-year-old Gauthier, who tasted success prior to embarking on her music career as the owner of a well-reviewed Southern-style eatery in Boston’s Back Bay, the Dixie Kitchen. Although she sold the restaurant to pursue music full-time (a move she says was "probably the most frightening thing I’ve ever done"), she was thoughtful enough to title her 1997 debut Dixie Kitchen (Groove House).

Gauthier allows that her lyrics are somewhat autobiographical, but she prefers not to distinguish between fact and fiction in her writing: "It’s not about me, it’s about the songs." She concedes that she grew up a gay kid in Thibodaux, Louisiana, after being adopted into a conservative family. A natural black sheep with a substance-abuse problem, she saw the inside of jail cells, ran away from home, and took refuge with fellow outsiders, including addicts, persons living with AIDS, and a group of protective drag queens before she sobered up, studied philosophy at Louisiana State University, and eventually attended the Cambridge School of Culinary Arts.

The songs on Filth & Fire offer snapshots of her wilder days; many are inspired by the characters who came in and out of her life during those rough-and-tumble years. Whiskey-soaked adulterers and jumpy cokeheads appear in "Camelot Motel," which she delivers in a wry and forlorn deadpan alto backed by a seasoned, rootsy band led by the CD’s producer, former Lucinda Williams collaborator/guitarist Gurf Morlix. An intimacy-fearing loner turns up in "Walk Through the Fire," a track filled with desperate emotions that seem close to Gauthier’s heart. "The powers that push me/They move me they own me/They constantly tell me to run," she sings plaintively. Does Gauthier herself have a fatalistic view of romance? "I think the word is realistic. I hope for the best, but it doesn’t usually work out that way."

Like Dixie Kitchen and the 1999 follow-up, Drag Queens and Limousines (Groove House), Filth & Fury relies on the emotional impact of Gauthier’s lyrics and on her ability to convey both immediacy and intimacy. Flowery prose and lofty poetics are not part of her repertoire. The autobiographical "Goodbye" begins, "Born a bastard child in New Orleans to a woman I’ve never seen . . . "

"I get to the heart of whatever it is that’s going on," she says, citing John Prine and Nanci Griffith as two of her musical influences. Although she’s lived in Nashville for two years (a move she made after having lived in Boston for 15), she feels little kinship with the flashy products churned out by the Nashville establishment on Music Row. "The great writers don’t sell as well as the kids that look great on television. I’m coming from the old Nashville — 1972, when Merle Haggard was still relevant."

Like Haggard and his kin, Gauthier cuts a distinct figure on stage, with her cropped hair, butch stance and twinkling blue eyes. "I enjoy it up there," she says of performing. "It’s taken a few years to work out all the phobias. I’ve made every possible mistake, so I have the confidence that comes from knowing that no matter what happens, I’m going to be just fine."

Mary Gauthier opens for Buskin & Batteau this Friday, April 4, at the Somerville Theatre; call (617) 931-2000.