A note on cultivars and their names

Cultivars (cultivated varieties) are extremely important in horticulture. By naming a single genetic individual (clone) the cultivar concept is valuable in two quite different ways. Firstly, it allows us to distinguish horticulturally significant points within the diversity of a species. They might be distinct in a way rarely seen in wild plants – variegation, double flowers etc; they might bring together characters found in quite distinct populations growing hundreds of kilometres apart, in entirely new combinations; or they might be individuals of a type that could quite easily be re-found in wild populations, simply horticulturally valuable points on the continuum of variation, perhaps taller or more dwarf, larger flowered or more richly coloured individuals. They may have been selected from a batch of wild origin seeds or be the result of within-species pollination in the garden. Such cultivars do not stand apart from the ‘true’ species, they belong to it.

Secondly, the cultivar allows us to name garden hybrids in a way compatible with the nomenclature of wild plants. Botanists often describe nothospecies occurring in wild populations (e.g. Abies × umbellata) but relatively few arising in horticulture (e.g. Magnolia × brooklynensis for all hybrids involving M. acuminata and M. liliiflora): cultivar names can be given to especially distinctive clones within such hybrid species, for example M. × brooklynensis ‘Yellow Bird’. In cases where a hybrid has particularly complex or uncertain parentage, cultivars are correctly listed under the generic name only, hence Magnolia ‘Aphrodite’ or Acer ‘Candy Stripe’. We prefer to describe cultivars under the species or nothospecies to which they belong, allowing easy comparison of varieties which often have a great deal in common, but in cases of complex or uncertain parentage cultivars are listed under the generic name only. In significant genera with very many cultivars, such as Magnolia and Malus, we list all cultivars in alphabetical cultivar pages (Magnolia Cultivars A etc), where we also cross-reference cultivars belonging to species and nothospecies.

Cultivar names are subject to precise, conservative rules much like those for scientific species names, designed to minimize ambiguity and duplication, and to maximize stability (Brickell et al. 2016). Importantly, there is a rule of priority: the first validly published name is the correct one (with certain caveats). In recent decades sections of the nursery trade have increasingly used trade designations – little-regulated marketing names for plants which normally also have a valid cultivar name. Some are registered trademarks, some not; many apply to cultivars subject to plant patents or other legal protections, others do not. They are not written in quotes and are distinguished by a different typeface, and often, as here, appear in block capitals, viz: Magnolia SHIRAZZ™ is a trade designation of the cultivar Magnolia ‘Vulden’. More than one trade designation may be given to a single cultivar, sometimes in different parts of the world. More confusing still, protected varieties are often given formal cultivar names which appear meaningless, do not always make pronounceable words and in practice force growers and gardeners to use the trade designation, with any legal restrictions it may carry. For example, Magnolia grandiflora BABY GRAND® is a trade designation of M. grandiflora ‘STRgra’. All this poses a problem for us in listing cultivars.

Before the advent of trade designations, few would have argued against using the accepted cultivar name for the primary listing, even if a synonym is quite widely familiar. To list Magnolia virginiana ‘Mattie Mae Smith’, while treating its selling name MARDI GRAS as if it were a synonym seems uncontroversial. Conversely, to give Magnolia ‘Micjur05’ as a primary listing rather than M. FAIRY MAGNOLIA WHITE might appear contrary or pedantic. But where to draw the line? There are many cases where an odd-looking, unfamiliar cultivar name is perfectly useable in everyday speech (M. ‘Vulden’ is easy for English speakers to say, and reflects its parentage, denudata × ‘Vulcan’; plenty of familiar cultivar names in other genera originated in the same way). And where there are multiple trade designations, which one should be used, especially when addressing an international audience? This last issue may become more prominent as plant breeders’ rights and patents expire on cultivars whose familiar trade designations are also trademarks. A nursery might then be free to propagate and sell it without a licence, but would either have to use the unwieldy cultivar name or devise a new trade designation.

In Trees and Shrubs Online we always use the accepted cultivar name, however ‘silly’ the name, as the primary listing. In certain genera, e.g. Magnolia, we always give a secondary listing under the trade designation, with a link to the primary listing. We are not happy about this situation, but would be equally unhappy with any of the alternatives. This is not a problem of our making, nor one created by the individual plant breeders whose work does so much to enhance our gardens; rather it is one made by the commercial system in which they have to operate. When referring to such plants most growers, amateur or professional, will use the trade designation in ordinary speech and on labels, and it is entirely admissible to do so: these are valid names, just not formal cultivar names.

This note is adapted from the generic introduction to Magnolia, written by Dr Julian Sutton.