The International Code of Nomenclature for Cultivated Plants (ICNCP), also known as the Cultivated Plant Code, is a guide to the rules and regulations for naming cultigens, i.e. plants whose origin or selection is primarily due to intentional human activity. Relevant to the Canna, the cultigens under the purview of the ICNCP are cultivars and Groups (cultivar groups), and this encyclopedia is based on that approach.
A cultivar is any new plant that comes about in cultivation (rather than in the wild). This is regardless of whether the new plant was ‘planned’ – the result of a plant breeder deliberately hybridising (crossing) two plants of the same genus – or whether it is an accident – the result of plants doing it themselves!
The cultivar name is written <Genus><species><‘CultivarName’>, for example, Canna iridiflora ‘Ehamanii’. Etiquette demands that a capital letter is used for the cultivar name and that it is in quotation marks.
Unfortunately, the species background of nearly all canna cultivars is extremely complicated and most are lost in time, or the names and background of the parents are simply unknown. In those cases the species section of the cultivar name is omitted. Eg. Canna ‘Madame Crozy’.
A hybrid is a new plant that is the result of a cross between two botanically distinct species. The name x Genus species. Most crosses occur at species level. For example; Canna x Annei , which is as a result of crossing Canna indica var.warszewiczii with Canna glauca.
The word cultivar originated from the need to distinguish between wild plants and those with characteristics that arose in cultivation. The word cultivar is a portmanteau of cultivated and variety, and describes plants raised in cultivation which differ sufficiently from their wild ancestors or, if taken into cultivation from the wild, are worthy enough of distinction from wild populations for horticultural purposes to merit special names.
Plants that can be considered as cultivars include:
- deliberate hybrids
- accidental hybrids in cultivation
- selection from existing cultivated stock
- selection from variants within a wild population and maintained as a recognisable entity solely by continued propagation
Hybrids, which are created sexually, can be either maintained asexually or by seed. F1 hybrids, which require to be re-created for each new generation, qualify as cultivars if the cross produces stable, repeatable forms.
A Group is united by some common trait; for example there may be a Group of yellow-flowering cultivars, a Group of cultivars with variegated leaves, a Group of cultivars resistant to a particular disease, etc. A cultivar may belong to more than one Group (for example, it may be yellow-flowering, with variegated leaves and resistant to the disease at one and the same time).
The ICNCP defines a standard form of nomenclature for cultivar groups. A group epithet, each word capitalised, is followed by the word Group and is un-italicised. Eg. Canna ‘Endeavour’ (Aquatic Group).
Obsolete naming conventions
Various attempts at grouping cannas have been advocated over the centuries, and other genus have done likewise. The need to have a universal naming mechanism has resulted in the ICNCP. The canna naming conventions made obsolete include:
- x floriferous
- x hortensis
- x iridifoises
- x orchoides
- x generalis
A recent innovation has been the realisation that the above nanospecies names are obsolete, and instead naming all canna cultivars as x generalis. Now, x generalis has a strict definition specified by its originator, Liberty Hyde Bailey. The misuse is rather futile as its only effect is identifying that the plant is a cultivar, whereas the ICNCP etiquette of identifying a cultivar by using a a capital letter and surrounding it with quotation marks already does that.