At the end of “White Oleander,” a drama based on Janet Fitch’s Oprah Book Club selection, the main character, Astrid, slowly closes each of the diorama-like suitcases she has created to document the stages of her life.

Astrid’s long blond braid has just the right amount of looseness; her artist’s studio has just the right amount of messiness; and even her hands are speckled with just the right amount of paint. Then the voice-over narration swells to the perfect passionate-yet-tempered pitch, and Astrid neatly closes the last diorama with — you guessed it — the perfect mixture of delicacy and firmness.

That’s exactly the problem with “White Oleander”: like Astrid’s dioramas, the movie is too perfectly packaged. Yes, there are some harsh, gritty themes here — dealing with a passionate narcissist of a mother, navigating the foster care system — but they’re tidily cut into bite-sized pieces that even Oprah could swallow.

It didn’t have to turn out that way. “White Oleander” has a promising, juicy premise: Astrid (Alison Lohman) is raised by her fiercely free-spirited mother Ingrid (Michelle Pfeiffer), a multimedia artist who likens the two of them to Vikings and brushes away society’s constraints. But when Ingrid takes revenge on a lover who dumped her, she ends up in prison for murder, and Astrid ends up drifting through strange foster homes with even stranger foster parents.

There’s the ex-stripper-turned-born-again Christian (Robin Wright Penn) who retains the fashion sense of those in her former profession and baptizes Astrid in her swimming pool. There’s the failed, unstable B-movie actress (Renee Zellweger) who needs Astrid’s company in order to deal with her near-abandonment by her cheating husband.

You might be wondering why Astrid couldn’t be placed in a “normal” foster home for a while, operated by some tired middle-aged couple out to earn a few bucks. That doesn’t happen here. But to their credit, the actresses handle melodrama with astounding competence, making relatively unbelievable caricatures believable.

Wright Penn is mesmerizing as what Pfeiffer’s character nicely terms “Bible-thumping trailer-trash.” And Zellweger, who tiptoes around her whitewashed Malibu home, is understated but convincing in her fragility.

Newcomer Lohman holds everything together, effectively and efficiently handling the plot’s twists and turns. She goes from innocent Bohemian love child to hardened street punk and back, never losing her quiet intensity and keeping the movie interesting. Her scenes with fellow foster-care child and love interest Paul (Patrick Fugit of “Almost Famous”) are some of the best in the movie, nicely tempering those with Pfeiffer.

Reeling off lines like “Love humiliates you. Hate cradles you,” Pfeiffer’s character certainly doesn’t provide much to work with. Pfeiffer tries hard — really hard — to pull off her passionate, defiant free spirit and make a truly unbelievable character work. But as usual, Michelle Pfeiffer manages to pull off only — Michelle Pfeiffer.

But it’s hard to blame anyone for ruining “White Oleander.” Everyone involved, including British director Peter Kosminsky, seems to try so hard. All the elements are there — including a beautifully surreal visual quality. But in trying to both escape and embrace its Oprah-ness, this movie fails to make it above mediocrity.

After two hours of wavering between a realistic, difficult coming of age tale and a nicey-nice Oprah format, “White Oleander” succumbs to what popular culture demands: the gritty, tough stuff is there. But like Astrid’s artwork, it’s constricted, too carefully put together, and in the end, too easily laid aside.