The title character of “Redwood,” the musical that opened Thursday night at the Nederlander Theatre, is a humongous northern California tree. 

Ancient and impressive, the centuries-old conifer makes a striking entrance on the stage, commanding attention as it looms over the five actors. Designed by Jason Ardizzone-West, the grand set piece is so large that star Idina Menzel and the cast can climb it using ropes and harnesses.

Too bad the Broadway show named after the wooden giant is a toothpick. 

The narrative revolves around Jesse, a woman from New York on the verge of a breakdown, who flees to the forest out west on the first anniversary of her son’s passing. The play “Redwood” offers a simplistic portrayal of grief, relying heavily on a blatant central metaphor: Jesse embodies the tree, with all its roots and connections.

In a state of disarray, Jesse impulsively embarks on a journey to the opposite coast without informing her wife Mel, a photographer who is somewhat sidelined in the story. Not even a cryptic hint like “so if you care to find me, look to the western sky” is enough to clue Mel in on Jesse’s sudden escapade.

Once in Eureka, Calif., in the wilderness strikingly depicted on large screens, she stumbles upon a pair of scientists. 

Despite traveling thousands of miles to take a hike, Jesse’s not a nature girl. “I hate greenery,” she proclaims. “If I even think about grass, I get Lyme Disease.” 

Indeed, writer-director Tina Landau has all her characters abruptly announce their defining traits like they’re on “The Dating Game.” 

When Jesse meets Finn (Michael Park), a veteran climber and optimist, he proudly says, “Got my head in the clouds!” 

His younger colleague Becca (Khaila Wilcoxon), irritated and skeptical, quickly retorts: “Got my feet on the ground.” 

Got my head in my hands. 

Jesse, normally a risk-averse workaholic, is immediately compelled to ascend the redwood that the duo has been studying. Finn, a kindhearted hippie, is on board with the idea. But rule-abiding Becca is adamantly opposed. (Clouds! Ground!). That muddled character, whose volcanic anger only exists to drum up conflict where there otherwise is none, is the worst-written in the show. 

Wilcoxon wows anyway with her powerful voice, but it gets wasted on composer Kate Diaz’s loud and repetitive ballads. One, in which Becca explains how the redwoods witnessed “human history’s growing pains,” is a lecturing “We Didn’t Start The Fire” that packs in the birth of Jesus, the writing of the Magna Carta and the Civil War. Lofty! 

Predictable as sunset, Jesse still goes up and Menzel straps in. The aerial sequences, in which the actors push themselves off the tree and spin around while accompanied by lush orchestral music, are supposed to be euphoric and life-affirming. “I’m flying, Jack!” That kind of thing. At best, however, they’re surreal. 

Menzel’s songs are tailored to the actress’ pop belt, which is thrilling in parts and wobbly in others. As she wails lesser versions of “Defying Gravity” and “Let it Go,” you sense the creative team’s mantra was “give the people what they want.” What we want, though, is Menzel now — not Menzel in 2003. I was worried she wouldn’t make it through some of the trickier numbers. She moves closer to 2025 with her maternal acting. 

Alone and making camp hundreds of feet in the air, Jesse battles the unforgiving elements and her own buried fears and insecurities. In a stormy monologue, Menzel vulnerably inhabits a mother who’s both running to and from the memory of her son Spencer, even if her quick-cut, poetic speech could end with “Moo with me!” 

The musical, which premiered in San Diego last year, also presciently concerns west coast wildfires.

There’s trauma after trauma. Yet what’s so puzzling about “Redwood” is that it’s a textbook tearjerker — a mom in mourning rediscovering herself midair, weighty speeches about losing everything — that leaves your eyes totally dry. 

The closest the musical comes to being remotely affecting is a quiet song toward the end called “Still,” beautifully sung by Zachary Noah Piser as Spencer. 

Jesse’s winding explanation for her son’s death should be scrapped and completely rewritten, but Piser has a velvet voice and an easily emotional presence regardless. 

“Redwood” gave me a renewed appreciation for “Into the Woods” and its composer-lyricist Stephen Sondheim. His show has the same themes, and the song “No One Is Alone,” softly sung by Cinderella, is a wise meditation on loss among the leaves that goes straight for the soul. 

There’s nothing half so deep from Elsa.