The birthday play was written with obvious love for the stage by Nagle Jackson (A Hotel on Marvin Gardens), whose plays have come alive before on Hedgerow's stage and whose adaptation of A Christmas Carol is a Hedgerow staple.

When Hedgerow first announced a special play to mark its many years, I'll admit that warning sirens blared in my head - the idea is ripe for icky self-congratulation. But Kafka in the Hedgerows is no vanity plate for a local theater's vehicle. Although clearly about Hedgerow's founding, and set in the very theater where it's staged, the play is impressive for its failure to pat Hedgerow's back. Instead, it heralds a larger truth: Theater, at its best, makes you think hard about the way the world works.

Jackson, former artistic director of the Milwaukee Repertory Theater and Princeton's McCarter Theatre, probably is the playwright closest to the spirit of Hedgerow, widely credited as being the nation's first resident repertory theater. One of his actors at the Milwaukee Rep was Penelope Reed, now Hedgerow's producing artistic director. She later joined his company at McCarter before moving to Hedgerow with her husband, Zoran Kovcic, and son, Jared Reed, both also part of the Hedgerow company. (Kovcic, generally Hedgerow's set designer, doubles as an actor, and his trademark is exasperation; no one in Philadelphia can match him for onstage vexation.)

The theater, in a stone-walled 1840 grist mill in Rose Valley, just outside Media in Delaware County, was created in 1923 by New York actor-director Jasper Deeter. He believed in the future of an ensemble company outside New York long before there was any real concept of regional theater.

After cajoling artisans using the old mill as a community center - apparently no simple negotiation - Deeter took over the space with $9 in his pocket. Actors of national stature eventually came to Rose Valley, and Hedgerow became an intellectual oasis for theater artists, a nonprofit stage in a for-profit theater world. New works debuted, new theater companies spun off.

Kafka in the Hedgerows is a comedy that fictionalizes Deeter's arrival and his tribulations in producing the first play. Jackson, who also directs, calls the founder Manfred Wolf, and brings him to Delaware County for the same reasons Deeter came - to escape New York's commercialism, to forge a stage that grows with its community, to experiment with an art form.

Into Wolf's new enterprise come community novices and veterans: Tatty (Susan Wefel), stager of the town's constant Gilbert and Sullivan operettas; Carrie (Lena Mucchetti), the daughter she keeps on a tight leash; Bobby (Kevin Meehan), the townie kid who can act but doesn't know it; Andromache Hobbs, devoted to Greek classics and set on having her own play produced. Wolf produces it - sort of.

And comes a foreigner, a young European who can finish nothing he sets out to write - Franz Kafka. A stranger, yes, but a kindred spirit to Wolf, for Kafka, too, longs to find a new way of making art that will be as rebellious as it is resonant. The Hedgerow community accepts him, cautiously, and then Dora (Michelle Eugene), his girlfriend, arrives with a revelation or two.

Reed plays Andromache Hobbs, and Kovcic is (a slightly exasperated) Rusty, who maintains the theater. Paul Kuhn, a former Hedgerow member, returns to play Wolf with anxious determination. Jared Reed makes a charming, believable Kafka, even if his accent does wander offstage from time to time.

The play turns sharply in Act 2, when Andromache, suffering because her play is being cobbled into another, less conventional work, takes on a dimension we have not seen before. But Reed deftly makes it work, and from there on, Kafka easily executes a heavier assignment: pitting the characters' lives against the roles they play, then projecting that tension to the idea of creating a theater that matters.

It's been a heady year for Hedgerow. This is the company's first season as an Actors Equity house, meaning that it's able to hire professional union actors and stage managers. (Actors who worked there, then became professionals, now can return.) Jackson's play, and Hedgerow's production, celebrate not just a birthday and a new status but a history that speaks to an art form that continues to matter.

Kafka in the Hedgerows

Through May 18 at the Hedgerow Theatre, 64 Rose Valley Rd., Rose Valley. Tickets: $10 to $30. Information: 610-565-4211 or www.hedgerowtheatre.org.