Each time Katherine Heigl acquires a ghastly new bridesmaid’s frock in “27 Dresses,” she’s told, “You can always shorten it and wear it again.”

That recycling esthetic is the guiding principle of the film, which reuses every tired plot twist in the wedding-comedy pattern book. It should have been shortened more. A lot more.

Heigl brings a game dedication to the part of Jane, a Manhattan eternal bridesmaid hopelessly infatuated with her boss, George (Ed Burns). She has adored him from close range for years, patiently waiting for him to notice, and return, her ardor, dreaming of the day they will drive off into the sunset in a hail of confetti, streamers and rice. George, amiable but dense, sees her as nothing more than the nice colleague who fetches his coffee so cheerfully.

So, as a singleton lacking a social life, Jane has become the go-to girl for friends who need some reliable backup on their wedding day. In hopes of attracting positive matrimonial juju, perhaps, Jane has kept all 27 bridesmaid gowns in her closet, a collection of fashion misfortunes that would give “Project Runway’s” Tim Gunn an aneurysm.

Giving her dreams of nuptial nirvana a reality check is Kevin, a wry writer (James Marsden). Little does Jane know he’s the author of the chic newspaper wedding notices column that helps fuel her romantic fantasies. Having professionally observed orgies of wedding day excess for years, he’s understandably jaded about giving such a momentous launch to relationships that have a 50-50 chance of enduring. Heigl was luminous in last summer’s “Knocked Up,” but the mushy passivity of this part and Anne Fletcher’s lackluster direction put her at a fatal disadvantage. Burns looks almost morose as the easygoing blob George; it’s the sort of thankless part Ralph Bellamy would have played in the ’30s.

Only Marsden’s cynical reporter and Judy Greer as Jane’s prickly, quick-witted pal seem to be having any fun. “27 Dresses” could have come alive if someone had the idea of matching up those two sharp-tongued magpies, but that’s expecting too much imagination from a movie that is as conventional and formula-bound as a traditional wedding ceremony.