How does he pass the time?
"I spent the weekend dreaming of the overthrow of the capital system and the installation of a people's republic not dominated by the military-industrial complex of America."
Asked how he would like to be remembered, he replies: "Do I have to be remembered?"
He does. Even if he weren't one of America's most popular poets — his 1958 debut, A Coney Island State of Mind, sold a million copies — Ferlinghetti would still be known for his role in a censorship trial that changed the course of history.
On June 7, 1957, the San Francisco Chronicle ran an intriguing headline on page two: "Bookshop owner surrenders". A warrant had been put out for Ferlinghetti's arrest, for printing and selling "obscene" materials.
In particular, a volume by a young, unknown poet, Howl and Other Poems, by Allen Ginsberg.
The prosecutor, a self-proclaimed "specialist in smut cases", ignored Ginsberg's tragic, era-defining portrait of "the best minds of my generation destroyed by madness, starving hysterical naked", instead totting up the four-letter words.
Unexpectedly, the judge — a conservative Sunday-school teacher — found Ferlinghetti not guilty, declaring that unless a book "is entirely lacking in 'social importance' it cannot be held obscene".
That victory for freedom of expression paved the way for the American publication of Lady Chatterley's Lover and cemented the idea of the Beat Generation. The trial even had the Hollywood treatment, in Howl (2010), with James Franco as Ginsberg.
Ferlinghetti states that the Beats were self-mythologising from the start, because Ginsberg "was a very clever publicist for his group of poets. Without Allen Ginsberg there would not have been the Beat Generation. It was a creation in Allen Ginsberg's mind."
Though their friendship lasted until Ginsberg's death in 1997, Ferlinghetti kept himself at a remove.
"I was his publisher, not his playmate," he tells me.
City Lights Pocket Poets, which he ran from his bookshop, became a spiritual home for the Beats, introducing readers to the poetry of Jack Kerouac, Diane di Prima and Gregory Corso (who once raided the shop till; Ferlinghetti deducted the cash from his royalties).
Ferlinghetti's vision, though, was fiercely independent: "As for myself, I was never Beat." When Ginsberg tried to push "Ferl" to publish more of his friends, he replied: "I'm not out to run a press of Poets That Write Like Allen Ginsberg."
City Lights' eclectic list ranged from Denise Levertov and Malcolm Bradbury to William Carlos Williams and Pablo Picasso. As editor, Ferlinghetti had an eye for talent, sensitivity and patience. He wrote Frank O'Hara postcards for five years saying he would "starve" without a full manuscript for his Lunch Poems, before O'Hara finally handed one over.
City Lights' goal was to start "an international, dissident, insurgent ferment", open to hepcats and "Red Cats" (Soviet poets) alike.
Shunning the "Beat" label, Ferlinghetti preferred the term "wide-open" — which was how Pablo Neruda, another City Lights poet, described Ferlinghetti's verse when they met in Cuba in 1960.
Ferlinghetti's politics — he is a socialist pacifist — date back to his war experience. In the Normandy landings, he commanded a small submarine chaser, which was entitled to call in as many supplies as a battleship — a loophole he used to request a full set of the Random House Modern Library and copious amounts of "medicinal" brandy.
The war went by with Ferlinghetti "enjoying every minute", until he visited Hiroshima, weeks after the bomb.
"It made me an instant pacifist," he said in 1999.
"There was just three square miles of mulch with human hair and bones sticking out ... blackened, unrecognisable shapes sticking up on the horizon, teacups full of flesh ..."
In 1946 he moved to Paris to study at the Sorbonne — and met his future wife, Kirby, on the ship over. They had two children, Julie and Lorenzo, and separated in 1973, but remained close until Kirby's death in 2012.
Though Ferlinghetti is now settled with Lorenzo in North Beach, for much of his life he travelled compulsively.
"Why do I voyage so much? And write so little?" he once wrote on a bus to Mexico.
The youngest of five children, Ferlinghetti was born in Yonkers, New York, a few months after his father, an estate agent, died.
When his overwhelmed mother was committed to an asylum, he was adopted by his aunt Emilie — then Emilie's husband ran off, leaving her destitute. She had to send Ferlinghetti to an orphanage until she landed a job as a live-in governess to the Bislands, a wealthy family in Bronxville.
They were happy, then one day she left forever without a word. The Bislands, who had lost a son in infancy, adopted Ferlinghetti.
The most poignant moment in Little Boy is the unexpected arrival of his mother and brothers to the Bislands' home.
Aged 6, Ferlinghetti was forced to choose between the families: "He finally stuttered out, 'Stay here,' and that was it, as his true mother and brothers just went away and he only half realising at all what he had done, his whole life decided in an instant.
"My mother must have felt terrible about that moment," he tells me. Did he ever see her again? "It was the last time."
•Lawrence Ferlinghetti's Little Boy is out now