Drosera affinis. Sarracenia x swaniana. Pinguicula sp. "Tonala ANPA A." Nepenthes Sunset Songs. Dionaea 'Akai Ryu.'
Each of these different names has a punctuation style different from the rest. Why? Because each style represents a different classification in horticulture, a recognition of different kinds of traits an categories. Just as every word in the human language on its own conveys a unique meaning, so too do the rules behind how horticulturalists write out and represent the plants they have, the significance of each. Nowadays as there probably always has been there is an issue of individuals who do not care to punctuate plant names properly, or too unmotivated to add an extra letter, quote mark, or capitalization, but in doing so essential meaning for the names of the plants discussed is lost, especially when information is being passed on to new growers. How so? Some of the meanings to follow:
The standard for all Latin scientific names is well understood: Italicized where possible to distinguish from the rest of the writing, capitalized genus name first for grouping, and then lowercase species name for direct identity. Hybrids are also pretty easy: between genus and the species (or nothospecies, in their case) epithets, an "x" is added to represent a cross, or "hybrida" as the most technically pronounced term (most just use the short, easy pronunciation of "x" though).
From there, however, horticulture takes it further. In classifying, organizing, copyrighting, or simply identifying unique individuals or groups the various botanical societies and horticultural associations have developed rules and guidelines for varieties, cultivars, greges, nicknames, localities, and so on, all ruled over by the International Code for Botanical Nomenclature, or ICBN. This is where the further punctuation comes in, where the confusion enters, and where people start asking "why should we even care?"
Why? Because without it, information is lost, and more confusion enters. Call me pedantic perhaps, but hey, taxonomist, comes with the territory; nevertheless the rules stand for a reason.
With each punctuation, comes a different class: cultivars, probably the most familiar term nowadays, are short for "cultivated variety," and depending on the description, may be only a singular vegetatively propagated clone, or a unique lineage or group of plants with very particular defining characteristics. These are denoted by a non-Latinized (typically, and preferably) capitalized cultivar name, surrounded by single quote marks. As in the above photo, one example is P. moranensis 'Huahuapan.' Some cultivar names, though rare, are different merely by a letter or two ('Scarlet' vs. 'Scarlette'), making spelling a must when mentioning them too, otherwise one may be referencing the entirely wrong plant from what one wishes to talk about.
Another horticultural category is the grex. Depending on the strictness of definition used, greges may be any plants that fall within the category of a cross of plant species A x species B, or might be more specific to a particular clone of A x particular clone of B, or even different clones A x A or A x B (and as different as one individual clone might be from another, I'm preferential to the stricter version; more naming potential that way too). All offspring of the resulting cross are one grex, and from these cultivars might even be pulled. Officially registered grex names are only recognized by associations for orchids, but they are already used unofficially too by many Nepenthes growers (including myself), and have potential for use amongst genera like Sarracenia, Pinguicula, some Drosera, and perhaps others where hybrids are not always sterile and many clones of each species exist, creating huge variety in crosses.
Grex names are denoted with capitalized titles, typically non-Latinized but not always. But most importantly, these are capital names without any quotation marks at all. An example below:
The grex contains multiple plants, each recognizably different from the rest but grouped together by their parentage (cultivar 'Splendid Diana' (or hybrid x splendiana) x ventricosa "red"). By losing the single quotes, one can immediately recognize that it is not a cultivar, but is still a strictly horticultural variety (just one with much greater variation; each clone depending on the grower might or might not receive a letter or numerical or other denomination to identify). That each separate cross between different clones is a unique grex maintains recognizability of exact parentage as well.
Sometimes the line is blurred though, as in the example of Sarracenia 'Alucard'. 'Alucard' is a multi-clonal cultivar of the hybrid S. x moorei with the parentage of S. flava var. rubricorpora x 'Royal Ruby' (another x moorei cultivar). 'Alucard' is not itself a grex however; any particularly dark var. rubricorpora crossed with 'Royal Ruby' may produce offspring that fit the cultivar description, but it may also produce offspring with traits that do not fit. The cultivar-fitting and non individuals would all be in the same grex, as they came from one cross together, but only the plants that fit the 'Alucard' description can be bestowed the cultivar title. Other greges might also produce more 'Alucard' clones, as well as unfit siblings, but if produced from different parental clones of var. rubricorpora can't be classed as all the same grex either; each is unique to its own.
Double quotes are the most variable, and basically used for anything that is not officially recognized as a particular horticultural category. This may include references to localities (Drosera burmannii "Humpty Doo, Northern Territory Au") of which some locales are directly implemented into the names of new species (ie. N. sumagaya), unofficial Latinized varieties not yet described (such as the gracilis "var. nigropurpurea" in a picture earlier, or the rafflesiana "var. alata" plants often traded), nicknames or various descriptors ("Candy Stripe," "Pink Lid," "short teeth," and so on), or unregistered and therefore unofficial cultivars (such as S. "Daina's Delight," N. "Rebecca Soper," and others; dangerous, as according to the registration authorities anyone could take those names, slap them on a different plant, and register it and the namer of the original plant could do nothing about it). It is these unofficial designations, and the variety therein, that makes use and recognition of the styles and punctuation outlining the other terms so important.
A great example is Drosera burmannii 'Pilliga Red', a registered cultivar of a seed-propagated species. The name comes from the location where the original plants were collected, and other plants from that area may not look the same, but could be designated sill by location and perhaps a color ("Red, Pilliga"). Similarly, Sarracenia 'Hurricane Creek White' is a multi-clonal cultivar, but not all plants from "Hurricane Creek, Alabama" may fit the cultivar description. There are plants of P. moranensis "Huahuapan" distributed that are not the same as the cultivar moranensis 'Huahuapan', and confusing the two would be terrible for the recognition of the unique traits of the cultivar clone. As mentioned above S. 'Alucard' is a multi-clonal plant, some of the clones having been selected for further special traits like 'Alucard' "Prince of Darkness," which may yet be registered as a cultivar of its own but for now the unofficial extra title maintains a distinction from the rest of the cultivar clones.
Thus, when one describes a plant, for example, as Sarracenia Scarlet Belle, the meaning is lost. Those who are well-versed in the plant group in question likely won't have much issue, but folks who are new (and those are usually the ones asking what plant is what) don't get the extra meaning, or perhaps horticulturalists from other plant categories (like someone well versed in growing aroids or succulents or orchids) will see that name and assume a grex. After all, capital letters, no quotes, must be a grex term then! Thus a unique single clone is misconstrued. Should in the future someone find a particularly flamboyant example of Nepenthes sumagaya and decide to make it a cultivar, or a Drosera ultramafica from Mount Kinabalu with some distinct trait, they could easily name the cultivar from the location: 'Sumagaya' or 'Kinabalu'. It's not Latinized, the names are not registered in such capital form elsewhere in either genus, so it could be valid. Then, without the proper quotations and style, are we speaking of species, location, grex, or the cultivars themselves? To each category, the punctuation provides the significance, and immediate recognition. To new growers, an explanation of the terms then equips them to recognize immediately what others are talking about too, but only so long as the rules are followed.