At 17 she suffered a devastating spinal illness and was paralysed for the rest of her life. She began to keep diaries about flowers, the changing seasons, and birds and other creatures, all observed from her bedside window. This practice eventually led to the writing and publication of her first book, Daddy Longlegs, and His White Heath Flower, in 1885 under the pen-name Nellie Cornwall.

Later she came to devote much of her attention to Cornish folklore and legend. She collected and recorded many stories about the Piskey folk, fairies of Cornish myth and legend. She published most of her works in this category under her better-known pen-name of Enys Tregarthen.

After Tregarthen's death, the writer Elizabeth Yates edited her extensive unpublished materials for publication.

As Nellie Cornwall

• Joyces Little Maid (1900)
• The Maid of the Storm (1900)
• The Hill Of Fire (1901)
• The Little Don Of Oxford (1902)
• Little Gladwise: The Story Of A Waif (1909)
• Tamsin Rosewarne and her burdens (1910)
• Twice Rescued
• Halvard Halworsen
• Granny Tresawna's Story

As Enys Tregarthen

• The Doll Who Came Alive (1973) ISBN 0-381-99683-2
• Pixie Folklore & Legends (reprinted 1995) ISBN 0-517-14903-6
• Padstow's Faery Folk (Paperback)
• North Cornwall Fairies and Legends (1906)
• The house of the sleeping winds and Other Stories (1911)
• The White Ring (1949)