It took me a long time to finish watching A Tree Grows in Brooklyn this week.

The first time I sat down to watch, life interrupted after 90 minutes. In the days that followed, I found myself procrastinating about watching the rest. Having seen the film several times, I knew exactly what was waiting for me.

Both the 1945 film and the Betty Smith novel it’s based on have occasionally drawn charges of sentimentality. In 1943, Time called the book “an old-fashioned family pudding of well-baked corn.”

According to literary critics Gerald C. Cupchik and Janos Laszlo, “sentimentality often involves situations which evoke very intense feelings: love affairs, childbirth, death” but does so with “reduced intensity and duration of emotional experience…diluted to a safe strength by idealisation and simplification.”

A Tree Grows in Brooklyn’s final  45 minutes do include death and childbirth and the hint of a love affair, but I don’t believe the movie dilutes or simplifies the emotions it elicits.

As director Elia Kazan said when speaking about the film years later, “Real sentiment is good.”

Tree explores a real part of growing up—becoming aware of your parents as flawed human beings. After losing her beloved father, Francie has to learn to see both her parents in a new way—as imperfect people who have loved her as best they could.

The performers bring warmth and humanity to their roles and ground the movie in “real sentiment.”

Peggy Ann Garner as Francie and James Dunn as Johnny Nolan are excellent, especially in the pivotal scene on Christmas night. Kazan drew on issues in their personal lives—Dunn’s alcoholism and Garner’s worry about her father in the Air Force—to shape their performances:

I have a book about child actors that describes Peggy Ann Garner as “a plain but realistic looking young lady with straight blond hair and a ski-jump nose.” I don’t think that’s quite fair, but Tree accentuates her “plainness” to help make her believable as Francie.

“They were both like children. Jimmy Dunn was a beautiful child…I treated him and Peggy the same way. I also threw them together a lot. I would tell Jimmy about her father being away and how much she missed him. I got him concerned about her. And I would tell her she was important to Jimmy and got her to love Jimmy…there is a scene later where Johnny and Kathy (sic) decide he must tell Francie that she has to quit school and go to work. There is no other way to afford the baby that’s coming. Johnny goes in determined, but before he can get to it, she tells him how much she wants to be a writer and his resolve melts. I didn’t need to do a lot of schmoozing before we shot that seen, as important and emotional as it was. The values were obvious and by then Jimmy loved Peggy as his own. How could any feelingful person not want Peggy Ann Garner to be anything she wanted?”

The casting of Dorothy McGuire as Katie Nolan is the biggest weakness I find in the film. McGuire gives a decent performance, but her luminous movie-star looks seem out-of-place in the gritty environment Kazan creates.

The first time I read A Tree Grows in Brooklyn, at Francie’s age, I didn’t see what all the fuss was about. Only as looking backward, as an adult, could I feel the full pain of Francie’s awakening to “the way things really are.”

The older I get, I think, the harder it’s going to be to watch those final 45 minutes.