Growing Knowledge

A Plant Lover's Guide to Dahlias by Andy Vernon 2014. Timber Press, Hardcover 256 p. This beautifully illustrated book is a great acquisition for the Dahlia lover, the wannabe Dahlia lover, or any lover of beautiful flowers. The author is British, and the book was written in association with the Kew Royal Botanic Gardens. However, he does visit some Dahlia gardens in the U.S.A., including the Swan Island Dahlia farm in Canby, Oregon. There is not an abundance of books on Dahlias. Hence this one, with the author's perky and easy writing style, brings us a comprehensive book on how to grow and enjoy Dahlias.

It is packed not only with gorgeous pictures from the world of Dahlias, but also with knowledge to grow these fantastic flowers. The book informs on using dahlias in garden design, in containers, growing and propagation information as well as ways to display them as a cut flower. He includes several pages of brief descriptions of flowering annuals and perennials that can be companions of Dahlias. He describes the various types and sizes of Dahlias, a somewhat confusing array of information, but a necessary and useful guide to have when ordering Dahlias from catalogues.

Early on, he also describes a few of the wild species Dahlias, such as, Dahlia dissecta, D. imperailis, D. merchii, D. shearffii, and D. tenuicaulis. These species all have a single layer of petals, but have a delicacy not always found in the hybrid cultivars. He makes a case for the adventurous gardener to grow them as well as the hybrids. He then profiles over 200 hybrid varieties, organized by color, with information on type, height, and spread. Gorgeous color photographs bring the plants to life.

Being a Dahlia fancier, I had to count the number featured with the number that I have or have had in my own garden. Alas, I only had about 19 of the featured Dahlias and there were so many new beauties that I now want to acquire. I didn't need this book to know that, as the Swan Island Dahlia catalogue each winter challenges me with an awesome array of choices. Although the author does not grow lots of Dahlias, he found lots of folks to share theirs with him and his camera.

Andy Vernon explained some things to me that I didn't know about Dahlias. The reason there are so many sizes, forms and colors is due to polyploid chromosomes and the many possible resulting hybrids developed by breeders and hobbyists. Humans are diploid (2n) in chromosome pairing, but Dahlias have four times as many, being octoploid (8n). This apparently gives them lots of genetic possibilities that we are still learning about. In addition, many new cultivars are likely to be developed by plant breeders hybridizing new Dahlias from the 36 species of Dahlias found in the wild.

This makes it pretty easy for even an amateur to come up with a new Dahlia. Breeders are doing that regularly. There are over 20,000 named Dahlias, so if you planted a hundred every year it would take you 200 years to see them all and by then there would likely be another few thousands introduced. Dahlias are mutation prone, and I have seen Dahlias revert to one of their parents or something totally different from what I originally assumed I had planted. A Dahlia may have two differing flowers occurring from one tuber, apparently because of a spontaneous mutation.

• The book winds down with sections on:
• how to store tubers effectively and efficiently.
• dealing with pests, diseases, and disorders.
• information on how to hybridize Dahlias.
• avoiding the spread of viruses with unclean cutting tools.

If you are interested in Dahlias for landscaping or as a cut flower garden addition, or just want to know a lot about Dahlias, this book is a good place to start.