Critical response
Leaves of Grass received mixed reviews from film critics, with praise being given to Norton's dual performance. Rotten Tomatoes reports that 63% of 40 critics gave the film a positive review, with an average score of 5.66/10. The website's critical consensus states that "Edward Norton delivers one of his finest performances in Leaves of Grass, but he's overpowered by the movie's many jarring tonal shifts." Metacritic, assigned the film a weighted average score of 58 out of 100, based on reviews from 10 critics, indicating "mixed or average" reviews.
"Leaves of Grass has the structure and the elements of a classical Greek drama: There's treachery, mistaken identity, deadly plots, and ambition; that it takes place in the middle of Oklahoma is almost irrelevant", said Paul Constant. Roger Ebert gave the film four out of four stars, and stated that "Tim Blake Nelson's Leaves of Grass is some kind of sweet, wacky masterpiece. It takes all sorts of risks, including a dual role with Edward Norton playing twin brothers, and it pulls them off." He closed his review with "Here's a quote for the video box: 'One of the year's best!' No, Tim Blake Nelson...thank you." Gary Goldstein of the Los Angeles Times also gave a positive review, particularly praising that "Edward Norton turns in not just one but two terrific performances in "Leaves of Grass," an offbeat thriller that is deepened — rather than derailed — by its tricky shift from darkly funny to just plain dark." He also praised Richard Dreyfuss, Susan Sarandon, and Josh Pais for their performances. Neil Genzlinger of The New York Times gave it an "NYT Critics' Pick", and particular praised the actors, saying "Mr. Norton is a pleasure to watch, and so is everyone else." He also approved of how the "film keeps you deliciously off-balance: it's funny and unnerving at the same time." Lisa Schwarzbaum of Entertainment Weekly stated that "the movie bubbles with intellectual curiosity and narrative ambition. And for that I dig it, even if Leaves of Grass has the habit of swerving and sometimes lurching from tone to tone." She praised the acting of Norton and Keri Russell. On an A to F scale, she gave the film a B+.
The film was not without its detractors. Dennis Harvey of Variety stated that "Nelson's script isn't blackly comic or deep enough to successfully accommodate the introduction of jarring violence," and criticized the subplot of Pais' character, Dreyfuss' performance, and the "perfunctory" romance between Norton and Russell. He strongly praised Norton's acting, stating that his dual-role "is very much the main attraction, and reward, of 'Leaves of Grass.'", and also praised Nelson's acting, stating that "Nelson himself provides the most valuable support in the colorful if variable cast." Rex Reed of New York Observer was extremely critical, particularly of Nelson, saying "It's just another oblique backfire from Tim Blake Nelson, whose work as a writer-director in general wallows in a bog of mediocrity" and that "Nelson, a cornball actor at best, is over the top as a larcenous Pa Kettle of a redneck sidekick." He finished his review stating that "The mirror-has-two-faces-idea is nothing new. From Bette Davis in Dead Ringer to Sam Rockwell in Moon, dozens of seasoned actors have lit each other's cigarettes while the audience thinks it's seeing double, and they've done it in much better pictures than this one. In Leaves of Grass, it seems irrelevant and recycled—essentially nothing more than a gimmick that wears out fast." He gave the film a rating of two out of four.