Unreleased cross of P. kermesina & P. caerulea
Passiflora Cultivars and Hybrids
Often used interchangeably what is the correct use of these words? A hybrid is not always a cultivar and a cultivar is not always a hybrid.
Cultivar is a ‘portmanteau’ word, that is, two words joined together and shortened. It means ‘cultivated variety’. Simply, something that has been selected and cultivated by humans. A cultivar can have wild origins, e.g. a selection of a species such as Passiflora loefgrenii ‘Iporanga’, a plant collected from Iporanga in Brazil, or can be selected from a seed packet you have bought, seed from market bought fruit, or fruit or plants in your greenhouse or garden that have occurred naturally. e.g. Passiflora ‘Constance Eliott’, a white selection of Passiflora caerulea that occurs randomly from seed. Cultivars can also be created by human-induced hybridisation (i.e., breeding). Just as an example, the holly cultivar Ilex ‘Sparkleberry’ is a controlled hybrid between I. serrata and I. verticillata the U.S. National Arboretum released.
A hybrid is a plant created by cross pollination between two different plants to produce fruit with viable seed which is then germinated. The parents can be different species, different selections of the same species, a species and an existing hybrid or two different hybrids. Passiflora ‘Snow Queen’ is an example of a hybrid. Hybrids can also occur naturally in the wild, with some Passiflora such as Tacsonia and Dysosmia more prone to this than others.
A hybrid may by convention be named in one of two different ways: as a cultivar or as a ‘nothospecies’.
Cultivars must be registered through an International Cultivar Registration Authority (ICRA) and are regulated by the International Code of Nomenclature for Cultivated Plants (ICNCP). Typically, cultivars would fall into the category of manmade crosses or selections. Parents by convention are listed with the female plant first, and the cultivar name must conform to the following format. Passiflora in italics, then the hybrid name in single inverted commas and the name or names capitalised but no italics. e.g.
Nothospecies, on the other hand, must be published in a peer-reviewed scientific journal and follow the strict rules in the International Code of Nomenclature for algae, fungi, and plants (ICN). Often, nothospecies are natural hybrids that have occurred in the wild. The naming convention is quite different, again the species is in italics, followed by the multiplication sign x in lower case (no italics) then the chosen name, again in italics.e.g.
Other examples include Passiflora x exoniensis and Passiflora x violacea. These can occasionally be subdivided when the same parents have given rise to different distinct offspring. e.g. P. x violacea ‘Eynesford Gem’. This can also be shortened to P. ‘Eynesford Gem’
There has been understandable confusion as to whether Passiflora x belotii can or indeed should be written as Passiflora ‘Belotii’. The answer: it should not. Thanks to Dr. Harlan Svoboda for clarifying as to why.
Dr. Svoboda comments, “the ‘x’ must be used in this instance because the entity is a nothospecies (not a cultivar) and was named under the provisions of the International Code of Nomenclature. This means that even though it is a hybrid it is written with a single epithet name and then the ‘x’ to indicate it is a nothotaxon. See Article H.3 of the Code (excerpt below). This name was not published as a cultivar, which would follow the International Code of Nomenclature for Cultivated Plants and would require the cultivar name (not an epithet) to be written in single quotation marks. The latter would be the case for something like Passiflora ‘Lady Margaret’ which is a registered cultivar name for a particular hybrid and not a nothospecies.”
In 30 years of growing I have to date named only about a dozen hybrids, the best of which have been selected to be commercially available. See Riverside® Passiflora.