I just remembered that one of my favorite movies features fabulous, vintage American gardens from the 1960s, although it's not a movie about gardening.
It's called the Swimmer, and it stars Burt Lancaster who wears swimming trunks, and only swimming trunks, through the whole movie.
Allmovie.com says this:
John Cheever's "misery in suburbia" short stories, brief and to the point, have always proven excellent TV fodder. Director Frank Perry's The Swimmer, adapted for the screen by Perry's wife Eleanor, is a rare, and for the most part successful, attempt at offering a Cheever story in feature-length form. Dressed only in swimming trunks throughout the film, Burt Lancaster plays a wealthy, middle-aged advertising man, embarked on a long and revelatory journey through suburban Connecticut. Lancaster slowly makes his way to his split-level home by travelling from house to house, and from swimming pool to swimming pool. At each stop, Lancaster comes face to face with an incident in his past. Informing Kim Hunter that he once harbored a secret love for her, Lancaster is mildly upset by Hunter's indifference. Elderly Cornelia Otis Skinner is incensed at Lancaster's intrusion in her backyard and orders him to leave. At the next home, Lancaster tries to seduce the nubile Janet Landgard, who'd once baby-sat for his daughters, but she regards him as a silly old man. And so it goes: as each subsequent suburbanite peels off his self-protective veneer, Lancaster grows more and more disillusioned with what he thought was his ideal lifestyle. The more intensely painful episode is the confrontation between Lancaster and ex-mistress Janice Rule (this scene was directed, without credit, by Sydney Pollack). Thoroughly defeated, the all-but-naked Lancaster laboriously makes his way through the Connecticut woods in a blinding rainstorm, desperately seeking out his own home where he fully expects his "loving" wife and daughters to greet him. Not this time. Dismissed as too self-consciously "arty" at the time of its release, The Swimmer's reputation has increased over the last three decades thanks to constant late-night TV exposure. The film represents the first movie work of 22-year-old composer Marvin Hamlisch.
My highest recommendation.