Viewing the enormous diversity of flower form and size available in modern dahlias, it is difficult to realise that all are derived from a handful of very different species native to Mexico.
Registration
The RHS is the International Cultivar Registration Authority for Dahlia cultivars.
Registration of Dahlia cultivar names (42 KB pdf)
Registration of Dahlia cultivar names (Word document)
The RHS Dahlia Committee
The Committee is a source of expertise for the RHS, for advice on all matters regarding dahlias. It is a joint Committee composed of representatives from the RHS and the National Dahlia Society. The Committee is responsible for judging all individual exhibits of dahlias shown at the London flower shows, and at other shows where the Committee may meet. It is also responsible for selecting cultivars for Award of Garden Merit assessment (from trials) and for judging the Dahlia trial at Wisley.
RHS Exhibition Awards
RHS Exhibition Awards may be recommended to individual dahlia exhibits. Three awards for plants are available, the highest being the First Class Certificate (FCC), followed by the Award of Merit (AM) and the Certificate of Preliminary Commendation (PC). Anyone can put plants forward for such Awards on specified dates when the Committee meets. Contact the Committee Secretary for further details.
RHS trials
The long-term trial of Dahlia cultivars is a magnificent feature of the Trials Field at Wisley in late summer and early autumn. The Trial is judged by the RHS Dahlia Committee, primarily to recommend cultivars for the Award of Garden Merit. The judges also give two annual National Dahlia Society awards, the John Brown Medal and the Stredwick Memorial Medal. Anyone can put plants forward for trial on specified dates when the Committee meets. Contact the Committee Secretary for further details.
Award of Garden Merit
List of Award of Garden Merit Dahlia
Links
Further reading
Aylett, R. 1997. Dahlia 'Bishop of Llandaff'. The Garden. 122(9): 641. The story of one of the most popular dahlia cultivars for general garden use.
Elliot, B. 1998. A priceless legacy. The Garden. 123(10): 716-719. A biography of Reginald Cory and the story of his dahlia trials at Dyffryn.
Grant, M. 1999. Dahlias at Wisley. The Dahlia Annual 1999:44-45. The dahlia trial at Wisley and the work of the Joint Dahlia Committee.