Young love, so sorely tested by vampirism and zombification in “Twilight” and “Warm Bodies,” finds the road to romance sunnier in “Beautiful Creatures,” in which two teens pair up despite the fact that one of them is a witch in training.

The one-liners drawl from the lips of the South Carolina characters like Spanish moss dripping from the oaks in a script so witty it attracted Oscar winners Emma Thompson and Jeremy Irons and Oscar nominee Viola Davis in supporting roles.

Alden Ehrenreich gives a breakout performance as Ethan, a dreamer and square peg in the round hole of rural Gatlin, S.C. A high school junior who longs for the day he can escape his provincial life, he’s an incessant reader — Henry Miller, Ayn Rand, William Burroughs — and that manifests itself in his narration and his take on his town. (“They keep re-enacting the Civil War like it’s gonna come out different.”)

He’s jilted the pretty, but less bookish and more fundamentalist Emily (Zoey Deutch), but open to the charms of the “new girl,” a raven-haired vision who appeared to him in dreams. Lena (Alice Englert) is a 15-year-old Southern Gothic Goth Girl: dark and mysterious, an aspiring poetess with numbers tattooed on one hand and a sullen sarcasm that is catnip to Ethan.

He ignores the Mean Girl-mongering of Emily, the fear-mongering of the local fundamentalist crusader (Thompson) and the counsel of family friend Amma (Davis). Lena resists the warnings of her patrician uncle (Irons), a recluse who presides over an estate that once encompassed the whole town.

Of course they’re fated to be together. And the fact that she’s a witch, and that only he’s supposed to know? That just doubles down on the doomed love/forbidden love thing.

Veteran writer-director Richard LaGravenese (“Water for Elephants,” “Freedom Writers”) boiled the Kami Garcia-Margaret Stohl novel down to characters, sharp dialogue and a palpable sense of place.

The story arc has few surprises — the odd flipped expectation or character in disguise. We can guess the climax in the opening scenes and figure out the role the mysterious Amma and bombshell witch-coven cousin Ridley (Emmy Rossum), tarted up like a lingerie model, will play in that finale.

But there’s something so delicious when Brits such as Thompson and Irons sink their fangs — sorry — into Deep South dialect. Thompson devours scenery, supporting players and dialogue with every “Bless your heart, shooo-gah” in the script, and Irons curls his nonexistent moustache over every syrupy zinger.

The film bogs down in the usual attempts at reinventing witchcraft — “We prefer the term ‘casters’ ” — and burdensome research the kids have to do to ensure their love isn’t “doomed” after all.

Young Englert, daughter of the Australian director Jane Campion, is more girl next door than Cover Girl (i.e. Rossom and Deutch). She and Davis are tasked with giving the story pathos, but Englert’s real job is to hold her own with some of the finest actors to ever “Bless your heart” on the screen. She does.

It’s Ehrenreich who makes the romantic longing believable enough for us to root for these impassioned teens, even if we know what 17-year-old Ethan doesn’t: “15 will get you 20.”