Taxonomy
Alba, a white-flowered cultivar of the Judas tree, Cercis siliquastrum. © Jean Tosti
Cercis siliquastrum is 1 of only 2 European native representatives of the Caesalpinioideae, the other being the carob tree, Ceratonia siliqua.
The Caesalpinioideae is sometimes treated as a family but is now more usually a subfamily of the Fabaceae (Leguminosae).
Molecular work shows this subfamily to be paraphyletic - the tribe Cercideae, which contains Bauhinia and Cercis, is basal and sister to the rest of the family. It is distinguished by its palmate venation, the leaf halves showing independent nyctitropic movement.
Species
The genus Cercis comprises 7 species:
- 3 American
- 3 Asian
- 1 native European - C. siliquastrum
Cultivars
C. siliquastrum is represented in cultivation by several selections. The most widely grown is the rich magenta flowered ‘Bodnant’, selected from plants grown at the north Wales garden of that name.
‘Alba’ was awarded the Royal Horticulture Society’s Award of Merit from a plant grown by the Wellcome Foundation at Langley Court in Kent. It is rarely seen and was described by a recent guide as ‘curiously ineffective’.
A variegated form with green and ivory zoned leaves is also rare in cultivation.