The carnivorous plant is thriving. A profusion of green, as tall as a doorway, this unique specimen boasts grasping tendrils and a wide Venus-flytrap mouth bristling with teeth. A recording contract should be awarded to its rich, deep singing voice, which periodically calls out for human blood.

The botanical prodigy known as Audrey II is a bouquet of charisma in Constellation Theatre Company’s staging of the 1982 musical comedy “Little Shop of Horrors,” directed by Nick Martin. The show, however, as a whole is less flourishing than its scene-stealing flora. Although many of the performances are droll and vibrant, and there’s a tuneful orchestra, led by musical director Walter “Bobby” McCoy, the production overall has a musty, potted vibe. Audrey II may be a herbaceous exotic, but in this rendering, “Little Shop” feels very much the old chestnut.

With book and lyrics by Howard Ashman and music by Alan Menken, “Little Shop” follows a nebbishy flower-shop assistant named Seymour (Christian Montgomery) as he nurtures an odd plant that he has named in honor of his beloved co-worker, Audrey (Teresa Quigley Danskey). The bizarre-looking seedling brings sorely needed business to the Skid Row shop but then displays a taste for eating people.

Puppet designer MattaMagical conjures Audrey II with a series of striking creations, from geranium-size shoot to hulking green predator. Marty Austin Lamar voices the leafy monster, his resonant singing nicely meshing with the plant’s R&B numbers, and his expressiveness fusing with that of Rj Pavel, the puppeteer.

Montgomery’s stooped, bespectacled Seymour is distinctively dweeby, and Danskey’s version of the hapless Audrey — who longs to live in a Pine-Sol-scented tract home, with plastic covers on the furniture — is funny and endearing. Scott Ward Abernethy is obviously having a blast channeling Audrey’s sadistic-dentist boyfriend, as well as assorted cameo figures, and Robert John Biedermann dodders aptly as the shop’s cantankerous owner, Mr. Mushnik.

But the kooky world in which these characters move doesn’t feel particularly fresh or essential. The proceedings do perk up when the three street urchins — Chiffon, Crystal and Ronnette (the lively Selena Clyne-Galindo, Chani Wereley and Alana S. Thomas) — hold forth. Brash and opinionated, this trio often functions as a piquant Greek chorus, sometimes dressed in outfits that evoke the Supremes, with vamping gestures to match. (Frank Labovitz is the costume designer; Ilona Kessell choreographed.)

At one point, a brief but delectable sight gag has the street urchins deadpanning through a window, wearing sunglasses, while Seymour sings about a solar eclipse. The fleeting bit of business calls to mind the simple, inventive staging techniques (onstage musicians, colorful pageantry) that have allowed previous Constellation productions to create a sense of wonder and expansiveness on a pocket-size scale. Puppetry aside, no such feat has been realized in “Little Shop,” whose scenic design is by A.J. Guban: The Skid Row street the urchins prowl, and the adjacent flower shop, look as if they’ve come out of a can.

Even leaving aside its more successful performances and moments, the show’s campy humor and tongue-in-cheek sci-fi story will hit the right monster-mash buttons for some audiences as Halloween approaches. But to supply a wholly satisfying artistic experience — and to show why “Little Shop” is a must-see perennial — this production would need more theatrical Miracle-Gro.

Little Shop of Horrors, book and lyrics by Howard Ashman, music by Alan Menken. Directed by Nick Martin; music director, Walter “Bobby” McCoy; lighting, Sarah Tundermann; sound, Justin Schmitz; properties, Alexander Rothschild. About 2 hours. $25-$55. Through Nov. 17 at the Source, 1835 14th St. NW. 202-204-7741.