Dennis Hopper was considered for the role of Bud Stamper.
Jane Fonda tested unsuccessfully for the role of Wilma Dean Loomis. Natalie Wood and Diane Varsi made the final list with Wood eventually being chosen. Lee Remick was also considered for the role of Deanie.
Although Elia Kazan had planned to film the movie in Kansas, a severe drought forced him to relocate all shooting to New York state. The waterfall in the film is located in High Falls, New York, in the Catskills.
As filmed, this film included a sequence in which Wilma Dean Loomis takes a bath while arguing with her mother. The bickering finally becomes so intense that Wilma jumps out of the tub and runs nude down a hallway to her bedroom, where the camera cuts to a close-up of her bare legs kicking hysterically on the mattress. Both the Hollywood censors and the Catholic Legion Of Decency objected to the hallway scene, finding the bare backside unsuitable for public display. Consequently, director Elia Kazan dropped the piece, leaving an abrupt jump from tub to bed.
Depicts the first French kiss in a Hollywood film.
Even though they were supposed to be playing teenagers, Natalie Wood and Warren Beatty were approximately 23 and 24 respectively at the time of filming. As a result, Elia Kazan decided that the other actors who were to play teenagers in the film should be in their early to mid-twenties as a way to make it easier for the audience to accept Wood and Beatty as teenagers rather than as adults playing teens.
In the bath scene, Natalie Wood's wrist is very briefly revealed. She normally always wore a bulky bracelet or long sleeves to hide the protrusion of a bone in her wrist which she thought to be an ugly anomaly.
Incredibly - by today's standards - a Cedar Rapids, Iowa (USA) newspaper ad for this film says "No one under 16 will be admitted unless accompanied by an adult".
It is revealed that Bud's real name is actually Arthur.
Rumor had it that Natalie Wood and Warren Beatty were having an affair during filming which led to the breakup of Natalie's marriage to Robert Wagner. In reality the two stars didn't get along during filming and started dating after Natalie's marriage had ended.
The film's title comes from the poem, "Ode: Intimations of Immortality" by William Wordsworth: "Though nothing can bring back the hour of splendour in the grass, / of glory in the flower, / we will grieve not, / rather find strength in what remains behind."
The nightclub owner played by Phyllis Diller is Texas Guinan, a real-life New York nightclub owner of the 1920's. "Hello, suckers!" was her standard nightly greeting to her nightclub patrons.
While a clip was not actually seen (though dialog is heard), there is a scene in Pedro Almodóvar's ¿Qué he hecho yo para merecer esto!! in which the grandmother and her eldest grandson attend a showing of Splendor in the Grass. As they leave the theater, the poster (Spanish) is clearly seen in the background.