The English Rock Garden, the magnum opus of the great gardening writer, horticulturist and plant collector Reginald Farrer, is an indispensable A to Z guide to alpine flowers. When he finally reaches V, Farrer writes: ‘Viola brings this alphabet to the last great dragon in its path.’ But rather than offering fire-breathing terror, he presents a family of flowers containing both beauties and ‘dull and dowdy species’.