If you were to hazard a guess at Scotland's ten most prolific playwrights, you would home in on a few likely candidates. They might reasonably include Rona Munro, David Greig, Jo Clifford and Peter Arnott, for example. Arnott has just had his 80th staged; Clifford has exceeded 100; the others are snapping at their heels.

One name unlikely to come up would be that of Elizabeth Newman. Why would it? She is not known as a writer but as the artistic director of Pitlochry Festival Theatre. Since moving from the Bolton Octagon five years ago, she has had plenty on her plate, having overseen the opening of the theatre's idyllic outdoor Amphitheatre as well as a handsome 172-seat twin-level studio. "I'm biased, but I think it is the most beautiful studio space in Scotland," she says. That is enough work for anyone, let alone the many productions she had directed and a few she has designed.

But hiding in plain sight is Elizabeth Newman the playwright. It is not only that she is responsible for the adaptation of The Secret Garden just about to open in the Amphitheatre under the direction of Ben Occhipinti. It is also that, without fanfare, sometimes even without credit, she has turned out dozens more. Only because I asked the question does she admit The Secret Garden is her 36th play.

Elizabeth Newman, artistic director of Pitlochry Festival Theatre

Her productions of A Streetcar Named Desire and Brief Encounter have just opened and already she is beavering away at adaptions of two Chekhov short stories. Yet despite such industriousness, she squirms at being thought of as a playwright.

"I'm not an auteur, I'm a midwife," she says of her role as a director. "I serve the play. Therefore, I have always veered away from talking about being the adapter. It’s something I spend a lot of time thinking about and doing – it’s a fundamental part of who I am – but I've always got the impression from people that they just want you to do one thing. I've always wanted to do more than one thing, so I thought, if I just don't talk about the other things, that'll be all right."

All but two of the 36 scripts have been adaptations. Her two original plays were collaborations with other writers. That accounts for some of her modesty. Another reason is pragmatism: she writes to give her actors something to perform.

"Sometimes it's for necessity," says Newman, who has adapted a lot of children's stories for the stage. "I am in service to somebody else. I'm trying to bring into physical life what they intended. I wouldn't describe myself as a playwright but a dramatist, in that my job is to make that dramatic story clear to an audience, whereas other people take novels and become the authorial voice. I am at best the co-author, whether it is Hans Christian Andersen or Dostoyevsky, I am still serving them."

Yet ask her what lies behind her version of The Secret Garden, the children's classic about the orphaned Mary Lennox who revitalises a mournful Yorkshire house, and she answers with a playwright's passion. "I remember reading it and finding it really moving," she says of Frances Hodgson Burnett novel, published in 1911, which she first read when she was eight or nine.

"My maternal grandfather was my favourite person and was a gardener. He could make anything grow. Often in our family, seeds are given as a gift. It's the sense of wanting something to carry on. When my grandmother was dying, she ordered lots of poppy seeds that were given to people at her funeral and then we had a scattering. Gardens are also connected to heaven, peaceful places and where you go if you're not here any more."

She continues: "As a child, I found it really sad that Mary was an orphan, whereas when I grew up, I was profoundly impacted by Mr Craven losing his wife and the grief that meant he wasn't able to actively love his child."

Having built the Amphitheatre in the Explorers Garden adjacent to the main building as a way of performing safely during the pandemic, she is delighted to see its continued use for family audiences this summer. "What's great is our audiences love all the different spaces," she says. "The Amphitheatre has been magical for us. It was born out of that horrible time, but people arrived into it and something almost shamanic happened. People felt connected to the drama but also the landscape. They are excited to go back in there and the amazing six-acre botanical garden."

That is especially the case with her script for The Secret Garden, which is being published by Nick Hern Books, the first of her plays to make it into print. "I wanted to adapt it for the Amphitheatre and for it to be about how you cocoon people and then reveal this garden," she says. "The fact that you're going to be walking through the garden to get to the Amphitheatre and you'll be nestled in there has the potential to be magical."

Having been outed as a playwright, Newman seems eager to hide away again. After our interview, she writes with further thoughts: "I am a theatre maker. No more. No less. Sometimes you’ll find me making the brews, sometimes you’ll find me putting the words on the page and sometimes you’ll find me putting out the deck chairs… Whatever needs to be done to keep the show on the road."

The Secret Garden is at Pitlochry Festival Theatre from 7 July until 19 August, https://pitlochryfestivaltheatre.com/

Elizabeth Newman on adapting The Secret Garden for Pitlochry: 'It has the potential to be magical'