Hirayama (Shin Saburi) is a fairly ordinary Tokyo businessman in late middle age. He is not as hidebound by tradition as some, as indicated by the sage advice he gives to a friend whose daughter has run away to be married. But when a man named Taniguchi (Keiji Sada) shows up at his office one day and asks for the hand of his daughter Setsuko (Ineko Arima) in marriage, Hirayama flips out. Angry over not being asked before Taniguchi and Setsuko chose each other, Hirayama refuses to consent to the marriage. It eventually becomes clear that his daughter is going to get married anyway, however, and Hirayama is left to make peace with his daughter's wedding and Japan's rapidly changing culture.
- Arranged Marriage: The main story is about how these are going out of style in Japan. Hirayama gives a little speech about how his Arranged Marriage to Kiyoko turned out well, but that the modern generation has the better idea in letting young people choose their own partners.
- Bookends: Begins with workers at a railway station commenting on all the wedding parties arriving; ends with Hirayama on the train leaving to see his daughter and new son-in-law.
- Color Motif: After filming exclusively in black-and-white throughout a career that dated back to 1927, Ozu finally went to color with this film. And he went in whole hog, with a riot of colors throughout the movie, but especially the color red. There's red everywhere in this movie. Most prominent is a bright red teapot which shows up in every scene inside the Hirayama home, but there are other examples of red all over the place—purses, ashtrays, signs, barstools, placemats. Everywhere. This is no doubt referring to the "Equinox flower" which gives the film its name, and which is bright red. The equinox flower often blooms around graveyards and is associated with death.
- Hypocrite: At the wedding which starts the film Hirayama gives a little speech about how young people in 1958 Japan have the right idea by choosing their own mates. And when his friend Mikami goes to Hirayama for advice after his daughter runs off to get married, Hirayama dispenses wise and conciliatory advice to both Mikami and the daughter. But when his own daughter reveals her wedding plans, Hirayama flips out.
- Japanese Politeness: Can verge on Stepford Smiler at times, like when a friend of the family smiles broadly while telling Hirayama that she has "a chronic disease".
- Match Cut: There's an interior set—a hallway, with people passing in and out of the frame from left and right at the T-junction at the end of the hallway. The film then cuts to an exterior set, an alley with the same geometry and the same T-junction at the end, with people passing in and out of frame from right to left.
- Off-into-the-Distance Ending: Ends with a shot of Hirayama's train puffing off into the distance, as Hirayama leaves for a conciliatory meeting with his daughter and new son-in-law.
- Parental Marriage Veto: Hirayama tries hard to exercise this, not even for any specific reason, but just because he wasn't asked ahead of time. He eventually finds out that the veto is no longer in effect in Japan.
- Signature Shot: Contains all of the hallmarks of Ozu's style, including the tatami shot (shot after shot with the camera placed three feet off the ground, the height of someone kneeling on a tatami mat) and the shot-reverse shot with actors addressing the camera, used in conversations.
- Slice of Life: Typical of Ozu, this is a low-key drama dealing with a father and his conflicting emotions as his youngest daughter is getting married.
- A Storm Is Coming: This is an Ozu movie so it's a very low-key, Kitchen Sink Drama-style storm. But nonetheless the railway workers in the opening scene comment that "there's a storm warning out", foreshadowing the disturbance coming into Hirayama's life.
- Yamato Nadeshiko: A deconstruction of this trope, or at least documenting how the idea is changing, as proper Japanese women no longer have to ask their fathers' permission to get married.