Tales from the riverbank: Nature poet Alice Oswald on her own turf

'Dart', Alice Oswald's book-length poem about the West Country waterway, netted her poetry's most coveted award, the TS Eliot Prize. Her latest finds her wandering on the banks of the Severn by night. Stephen Knight goes to Devon to meet this intense and intuitive nature poet on her own turf

Within a few hours of leaving suburban London, I am in south Devon, in the modest cottage where the poet lives with her husband (the playwright Peter Oswald) and their three children. It's another world. A skipping-rope uncoiled in the doorway, trays of seedlings on the window-sill and, outside, the second day of spring: a hazy blue sky, wood pigeons, garden allotments clustered on a slope where the Oswald children are playing with friends, and the hills beyond. "I really think there are spirits in a place that you have to accommodate," Oswald says later. It is a surprisingly tranquil setting for a writer whose work is both complex and forthright, dazzling and tense with linguistic energy.

I first saw Alice Oswald at a TS Eliot Prize reading in January, 1997. At 30, the youngest on the shortlist, Oswald dispensed with chatty introductions to deliver the evening's extraordinary performance; "mesmeric in its power and intensity", to quote one report. When I met her last year – having just watched her hypnotise an audience of European academics – Oswald explained that the tension of that reading 11 years earlier was the result of having her hungry, four-month-old son backstage. True up to a point, no doubt, but Alice Oswald is charismatic, like anyone with an intense focus on their art. Diffident, clear-eyed and intelligent, she is prone to insecurity, and her reserve could be mistaken for aloofness. At the end of our interview, when she signed my copy of her latest book, I found a small, involuted signature like a tendril. Her poetry is bold but her manner is not.

The success of her work might have fuddled a lesser writer. Three of her four collections have been Poetry Book Society Choices; her second book, Dart, won theTS Eliot Prize; her third, Woods etc., won the Geoffrey Faber Memorial Prize in 2007. Her fans include Carol Ann Duffy and Jeanette Winterson. Last year, she was one of only five poets in a list, compiled by a newspaper's book critics, of the 50 greatest British writers since 1945; she was the youngest writer included. Yet Oswald is far from complacent about her two just-published books, Weeds and Wild Flowers (£14.99) and A Sleepwalk on the Severn (£7, both Faber).

She describes them both as taking "massive liberties". Perhaps this caution is to be expected from a poet who has a readership but is reluctant to repeat herself. It might have been tempting to produce variations on Dart, the book-length poem about the Devon river and the people on its margins which incorporated material gathered from interviews. Dart is a counterblast to the linguistically conservative vignette trimmed with images and closing with a wee epiphany, which has dominated British poetry for the past half-century. Oswald doesn't put pen to paper until the poem has formed in her mind – "I like the body to take part in writing a poem" – and she believes in "a whole poem which I just can't quite hear. It's a question of trying to take down by dictation what's already there. I'm not making something, I'm trying to hear it." In that spirit, why not read aloud the following lines:

you can hear water

cooped up in moss and moving

slowly uphill through lean-to trees

where every day the sun gets twisted and shut

with the weak sound of the wind

rubbing one indolent twig upon another

Sound is fundamental to Oswald's poetry, though never, she hopes, at the cost of sense. Negative reviews trouble her, especially if they question her meaning. "I hate not managing to speak clearly," she says, as agitated as she gets during our al fresco conversation. "I really hate it. I get a feeling of claustrophobia – like I'm locked in my own head – if what I've said hasn't reached someone." Nevertheless, Oswald would rather risk unintelligibility while being true to her inspiration. Last year, she published a selection of the 16th-century poet Thomas Wyatt's verse. Her introduction, impatient with the mangling his rhythms have suffered over the years, is a primer for readers both of the Tudor poet and of Oswald herself. "People are so used to reading novels now, they just read a poem straight through to get the meaning. And that's something totally different from the slow way you read something if it's a tune; which to me a poem has to be."

While Wyatt has influenced her thinking on versification, the writer to whom she feels most indebted is Homer. Still grateful to the teacher at a secondary school where she was the only pupil studying Greek, Oswald went on to take a degree in Classics at Oxford, avoiding the more obvious route for the aspiring writer of an English degree. Ted Hughes, a poet with whom she is routinely compared, was a relatively late discovery. The influence of Homer is present in the polyphony of Dart. She believes poems are much better if they are not written by one person. I suggest that there is, too, something of the exuberance of young children present in a work written by the mother of two small boys. "I was amazed by the excitement of these fresh, young minds in the house," she says, recognising "a much greater freedom in Dart, a willingness for other people to contribute. It felt like I'd opened my mind out."

The book which followed, Woods etc. (2005), includes poems written before, during and after her work on Dart. A recalcitrant, knotty volume, it works through that loss of singularity which has made lyric poetry harder for Oswald to write. With earplugs in, she works for a minimum of four hours when the children are at school or her husband is on duty. In contrast, her first book was written at night and in the early hours, after her days working as a gardener, a job she took up after university. It offered her a completely different way of appreciating the natural world. Tiredness destroys the logic of ordinary language, and she feels a nostalgia for her first book, The Thing in the Gap-Stone Stile (1996), which is "not so burdened by the need to make sense": "When a man went to fight a stone, / he clenched his knuckle-stones, he lifted his foot-stones, / he upheld himself like the last megalith."

That watery, moonlit, brilliant debut and the manner of its composition recall her beginning as a writer. Her first poem, prompted by a feeling of relief after a wakeful night in a frightening bedroom, was composed when she was eight. She has written poetry ever since, and reads the work of others "to be healed".

Both of Alice Oswald's new books are shot through with eeriness, fear entwined with a humour for which she is seldom credited. Commissioned by Gloucestershire County Council for performance by choral speakers this summer, A Sleepwalk on the Severn has Beckettian flashes Oswald hopes are not too overt. It is most definitely not a play, as the preface points out in its first sentence. (She does, however, admit that her latest writing tends towards drama, that she enjoys reading plays the way others read books of poems, and that, with her husband and a trumpeter friend, she has formed a group called The Attention Seekers to perform locally. She has considered writing poems to be read with trumpet accompaniment, which sounds eccentric. But why not?)

Her other book, the beautifully produced Weeds and Wild Flowers, is a joint production with Jessica Greenman, whose etchings are Gothic versions of Cicely Mary Barker's Flower Fairies illustrations, without the fairies. Oswald responded to the darkness of Greenman's work, and some of the poems occupy that nightmarish territory we reserve for our children: "I know I know / your noisy nose-blow/ and the grimly to-fro / fetching of scissors / by your long fingers / and your sly certainty / that there is still no remedy / for mortality / except mortality." The book already has the feel of a classic.

Before I leave, we walk to a spot overlooking the river Dart. I ask if she can imagine moving to the city. Perhaps, she tells me, when she is old. Of all the things she said in our interview – which at one point drifted into talk of magic – it's the one I find most unlikely, though, such is Alice Oswald's need to challenge boundaries and to match unmatchable forms, there is really no telling. I was pleased to discover, reviewing the tape on the train home, that it had picked up the birdsong which punctuated our conversation.