I recommend all interested should read the
International Code of Nomenclature for Cultivated Plants Eighth Edition (current)
Chapter II: Definitions
Article 2: The Cultivar
2.3. A cultivar is an assemblage of plants that (a) has been selected for a
particular character or combination of characters, (b) is distinct, uniform, and stable
in these characters, and (c) when propagated by appropriate means, retains those
characters (but see Art. 9.1 Note 1).
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9.1.Note 1. No assemblage of plants can be regarded as a cultivar or Group until its category,
name, and circumscription has been published. For a grex its name, category, and parentage
must be published. For the generic name of an intergeneric graft chimaera its name and
parentage must be published.
Articles 2.5 through 2.23 further define what is and what is not a cultivar. Contrary to popular believe a cultivar is not confined to a specific clone.
Examples:
2.12 An assemblage of individual plants grown from seed derived from
uncontrolled pollination may form a cultivar when it meets the criteria laid down in
Art. 2.3 and when it can be distinguished consistently by one or more characters even
though the individual plants of the assemblage many not necessarily be genetically
unfiorm.
Ex. 8. Ballota nigra 'Archer's Variety',
Delphinium 'Astolat',
Geum 'Lady Stratheden',
Lavatera
'Ice Cool',
Milium effusum 'Aureum',
Verbena hastata 'Rosea', and
Viola 'Penny Black' are cultivars
which are propagated from seed.
Ex. 9. When seed is sown of the yellow-fruited cultivar
Viburnum opulus 'Xanthocarpum', a
proportion of the resulting seedlings is indistinguishable from the parent plant; such progeny is to be
treated as being part of the same cultivar.
Ex. 10. The seed-raised
Betula pendula 'Penla',
Hlppophae rhamnoides 'Ram',
Larix kaempferi
'Palsgard Velling', and
Rosa Carolina 'Indabes' were selected from plants from known geographical
(Example: Sarracenia 'Hurricane Creek White')
2.13 An assemblage of plants grown from seed collected from a particular
provenance on more than one occasion and clearly distinguishable by one or more
characters (a topovariant) may form a cultivar.
Ex. 11. If considered distinguishable, plants such as
Picea abies of Dutch provenance Gortel-1,
Syringa vulgaris of a white-flowered Swedish seed source called Veberod, or
Eucalyptus
camaldulensis selected from especially fast-growing populations, could be treated as cultivars.
(Example:
Sarracenia 'Hurricane Creek White')
As far as progeny from selfed seeds:
2.20. In considering whether two or more plants belong to the same or different
cultivars,
their origins are irrelevant. Cultivars that cannot be distinguished from
others by any of the means currently adopted for cultivar determination in the group
concerned are treated as one cultivar.
Ex. 17. Some cultivars derived from branch sports of
Pittosporum 'Garnettii' are indistinguishable
and therefore belong to a single cultivar, even though these sports have occurred at different times in
different locations.
Pittosporum 'Margaret Turnbull', which originated in New Zealand, appears to be
identical with P. 'John Flanagan' from Ireland. The International Cultivar Registration Authority for
Pittosporum designated
P. 'Margaret Turnbull' as the accepted name, with
P. 'John Flanagan' as a
later synonym.
Ex. 18.
Dianthus 'William Sim' produces distinguishable mutants that by further mutation give rise
to a range of variants, some of which are indistinguishable from
D. 'William Sim'.
2.21. If a change in the method of propagation of a cultivar leads to a change in the
set of characters by which it is distinguished, the plants so produced are not regarded
as belonging to the same cultivar.
Ex. 19. The double-flowered
Campanula trachelium 'Bernice' is usually vegetatively propagated. If
grown from seed, it may produce a wide range of plants varying in height, degree of doubling, and
colour. Such seed-raised plants are not to be considered the same as, nor be named as,
Campanula
trachelium 'Bernice' unless the individual plants cannot be distinguished from this cultivar.
Ex. 20. Cereus hildmannianus 'Monstrosus' is a teratological form of a cactus that is generally
increased from cuttings. However, on sowing seed, a proportion of seedlings show the same
monstrose condition. Whichever way propagation is carried out, the same name is to be applied to the
monstrose plants that form the cultivar. The non-monstrose plants are treated as indistinguishable
parts of the species.
Ex. 21.
Hosta 'Halcyon' is vegetatively propagated, yet when increased by micropropagation a
number of mutants may be generated; one of these has been isolated and multiplied to form the
cultivar
H. 'June'.
Article 3: The Group
3.1 The formal category which may comprise cultivars, individual plants or
combinations thereof on the basis of defined character-based similarity is the Group.
The Rules for forming Group names are laid out in Art. 22 of this Code.
3.2 Criteria for forming and maintaing a Group vary according to the required
purposes of particular users. All members of a Group must share the character(s) by
which that Group is defined.