She did beautiful botanical illustrations of flowers from different seasons, and areas. My favorite books by her are Flower Fairies: of the Spring, of the Summer, of the Autumn, of the Trees, of the Garden, and of the Wayside. In these books each flower illustrated is accompanied by its own special faery guardian. Here are some examples of her magical illustrations, just click on the image to see it larger and get more information on the flower and the faery that represents it.

The above pictures come from the book, Flower Fairies of the Autumn. You can purchase this book and her other lovely books below:
 

A Treasury of Flower Fairies
by Cicely Mary Barker

Flower Fairies of the Garden : Poems and Pictures (Flower Fairies)
by Cicely Mary Barker

Flower Fairies of the Trees (Flower Fairies)
by Cicely Mary Barker

Flower Fairies of the Wayside : Poems and Pictures
by Cicely Mary Barker

Flower Fairies of the Spring (Flower Fairies)
by Cicely Mary Barker

Flower Fairies of the Summer
by Cicely Mary Barker

Flower Fairies of the Autumn : With the Nuts and Berries They Bring : Poems and Pictures
by Cicely Mary Barker

Flower Fairies of the Winter
by Cicely Mary Barker