Her name is synonymous with illustrated stories of anthropomorphic animals: a rabbit who steals lettuces, French beans and radishes from a curmudgeonly Scots gardener, a hedgehog laundress and a well-dressed frog who has an accident with a stickleback out fishing. Somewhere in the world, it has been estimated, someone buys a copy of one of what Beatrix Potter called her “little books” every 15 seconds.

In the 120 years since Frederick Warne first published The Tale of Peter Rabbit, Beatrix – author, artist and publishing phenomenon – has become a staple of children’s bedtime reading around the world: her stories have spawned film adaptations, cuddly toys, even wallpaper. But as a new exhibition at the Victoria and Albert Museum shows, any suggestion that hers is a world of whimsy is misguided.

Beatrix Potter: Drawn to Nature – which features more than 240 personal objects including letters, sketches and scientific drawings – reveals that the author had an abiding passion for nature from a young age. A sketchbook in the first section of the exhibition includes watercolours of different caterpillars drawn by Beatrix when she was nine, while another section reimagines the nursery shared by her and her brother, Bertram, at the family home in Bolton Gardens, South Kensington, where the siblings arranged a collection of butterflies, beetles, birds’ eggs, shells and fossils.

Significantly, Beatrix, who was born on July 28 1866, always said that her earliest memories were not of London, where she lived until the age of 47, but of waking as a baby in her crib, to the sound of birdsong coming from a nest in a hollow elm tree at her grandparents’ house in Hertfordshire (Camfield Place, afterwards home of the romantic novelist Barbara Cartland). This first alertness to nature never left her. Later, she learnt to climb the hollow tree trunk to spy on nesting owls and starlings. She never loved London, where she felt the rows of houses shut her in like “great frowning hills”.

As well as caterpillars, her first sketchbook includes drawings of rabbits. Like human beings, they walk on two legs, wear spectacles, struggle with an inside-out umbrella, and skim over ice or snow on sleds and sleighs. Although this sounds like quintessential Beatrix Potter, these images are quite different from many of her other early drawings and paintings. Until the sea change in her early-thirties that gave birth to The Tale of Peter Rabbit, her interest in nature was more scientific than fantastical.