Periodically on the garden blogs, questions will arise about whether common names or scientific names are "better" for some purpose or another. (The biggest recent such post I've seen was at Garden Rant.) I've seen people at Garden Web asking about whether or not they "need to know" the botanical names for everything, and I've been snapped at for using the botanical names at GW and at work both. And I thought maybe a post about all this might be in order. So.
I use the botanical names pretty much exclusively here at PATSP, because I think they're more useful, and also, as the sidebar says, because those are the plants' names. I don't ordinarily focus on the common names unless one is particularly stupid (as with "Timbuktu tree") or well-known (African violet), or unless I find myself saying the plant's name over and over and I need a synonym. (Food plants are exceptions.1) I also generally think in terms of the botanical names, to the point where I've had customers ask me for a common name for something and I've been unable to come up with one.2
This is not out of pretentiousness, or at least I don't think it's about pretentiousness. You have to understand, if I want to look up a plant on-line, or in a book, or order plants wholesale, the botanical names are what I have to know: common names are too localized and nonspecific, and I need to make sure we're talking about the same plant, you know? This may or may not be the case for you, but for me it's only natural to use the scientific name, and I don't consider it difficult or impressive. This is a chair, that is a table, over there is an Aglaonema.
I do appreciate that for a lot of people, the vernacular is a lot easier to pick up. Some people just don't acquire new words well, especially not new words that are weird. Still, you probably know fahrvergnügen, or sudoku, or et cetera, right?3 Dieffenbachia is not any worse than Haagen-Dazs or schadenfreude.
Plus you probably already know a lot of botanical names, even if you've never tried to learn them. Gardenia, Petunia, Aloe, Begonia, Ginkgo, Hibiscus, Philodendron, Hosta, Ficus, etc., are all official names, just off the top of my head.
Common names also tend to cause confusion. I've heard Dieffenbachia spp. and Kalanchoe pinnata called "mother-in-law plant," and Sansevieria trifasciata called "mother-in-law tongue." This might lead you to think that they're similar, but the three are not really alike at all. African violets (Saintpaulia) are not much like regular violets (Viola), either. Zebra plant (Aphelandra squarrosa) is not like zebra plant (Haworthia fasciata), zebra plant (Calathea bella), zebra plant (Calathea zebrina), zebra plant (Sanchezia nobilis var. glaucaphylla), zebra plant (Aechmea chantinii), zebra plant (Cryptanthus zonatus), zebra grass (Miscanthus sinensis), or the zebra orchid (Caladenia cairnsiana). You get my point.
This is not to say that there aren't issues with the botanical names being similar or confusing (it was a proud day for me when I realized that I finally knew the difference between Verbena, Viburnum, and Verbascum, for example), but at least the botanical names are actually all distinct, similar though they may be. You won't run into a situation like with the "zebras" above, where you have seven completely different plants with the exact same name. You also won't have the problem of the same plant going by totally different names depending on who you're talking to. As I mentioned in the Chlorophytum comosum profile, what in English is "airplane plant" or "spider plant" becomes "mala madre" in Spanish.
There is one pro-common-name argument that I'm sympathetic to, that some of the common names are pretty, or poetic-sounding, or have some kind of interesting historical background to them. I enjoy learning about that kind of stuff myself, and agree that it would be a shame to lose those names entirely. At the same time, though, the people who subscribe to this idea rarely stop to acknowledge that the same is frequently true of the botanical names as well. Dizygotheca elegantissima is just about the most perfectly appropriate name for any plant in any language: the name just sounds like the plant looks (to me, anyway).4 Soleirolia soleirolii (so-lay-ROW-lee-uh so-lay-ROW-lee-eye) is as musical as any English name you want to put it up against,5 and is vastly superior to "baby's tears"6 or "mind-your-own-business." Admittedly, history and stirring human trivia is not the strong point of a lot of botanical names, but there's certainly got to be some kind of story behind names like Chamaedorea elegans ("small, elegant gift"), Caryota mitis ("unarmed nut"), or Rhapis excelsa ("exalted needle").
Botanical names don't come without some special dangers of their own, of course. They can, for example, make possible a very special brand of douchebaggery, wherein a jerk will correct your pronunciation or ID or whatever just because s/he7 wants to look smart. Correcting pronunciation is particularly choady behavior, because it's unfair: not only do most of us see these names written out before we hear them spoken, so our first stab at a pronunciation is just a guess, but there's not exactly a "correct" pronunciation for most of these anyway. From L. H. Bailey:
There is no standard agreement on rules for the pronounciation of botanical binomials. Even in the best practice, there may be variations in pronunciation of a given word; this is unavoidable, and no more to be regretted than similar variations in pronouncing many English words. The particular sound to be given the vowels (within the categories "long" and "short") rests with the individual. Many persons pronounce generic and specific names simply as if the words were English, but for the most part the accent, at least, follows usage in Latin.8Things have probably changed somewhat since 1933: I'm sure if nothing else, someone somewhere has probably written up official pronunciation standards, but I think Bailey really has the saner approach for the low-stakes garden center / hobbyist area. What's important is that everybody knows what plant is being discussed, and whether it's HOOK-er-uh / HYEW-ker-uh / HOY-ker-uh or whatever is really awfully beside the point. Pronounce it the way you think it should be pronounced; if other people say it differently, adopt their pronunciation if it makes more sense, and don't if it doesn't. Things will work out. Don't be intimidated.
In any case, there's no excuse for people who work in the plant business not to know the names -- both names -- of the plants they're selling, and to include that information on the tags. Which was pretty much the consensus opinion on Garden Rant, by the end of it all. The people who are selling the plants need to know what they're selling, and what the customers are asking for. This is, or at least ought to be, pretty basic customer service: it's not that much to expect.9 As a customer, of course, you can know or not know anything you want, but if you only have time or motivation to learn one name, the botanical name is the one that's going to be worth more to you in the long run, I think. A lot depends on who you plan on discussing the plants with, and whether you anticipate becoming a collector: if you don't really care beyond having something in your yard that looks pretty and doesn't need a lot of work from you, learn either. If you're going to want to talk about them on-line with people from all over the world, or ask your local garden center for help with them, or do Google searches on them, the effort you put into the botanical names will pay off, I can just about promise. But, you know, don't feel obligated.
1 Food plants seem like an acceptable exception to me because most of the time when you encounter them, they're already separated from the plant and reduced to just the edible parts. Still technically alive, sure, but no longer the entire plant with roots and soil and leaves and the whole shebang. Somehow this makes it okay, as far as I'm concerned, to forget about the botanical name unless you really want to know it for some reason. But I only feel that way about food plants.
2 Anthurium andraeanum seems to be particularly bad that way. I've heard the names "flamingo flower" and "tail flower" used for them in books and stuff, but nobody I know uses those names for them: at work, everybody calls them Anthuriums, all the time, so when I have to use "flamingo flower" or something I always get kind of self-conscious about it. Somehow it ends up feeling like I'm making the name up on the spot, even though I'm not.
3 If you don't: fahrvergnügen is a word from a 1989 Volkswagen ad campaign, which means "driving enjoyment" in German. Sudoku is the Japanese name for the puzzles where you have to put all the digits 1-9 in a grid so that no row, column, or smaller grid within the grid contains the same digit more than once. Et cetera is a Latin phrase meaning "and the rest," which is presently in the process of being butchered into the Englishized "eksetera." At least as far as pronunciation goes. I'm usually pretty tolerant of other people changing pronunciations and spellings, but "eksetera" and "aks" and "ekspresso" all drive me up a wall. Something about the "ks" sound.
4 Which makes it all the more tragic that it's no longer correct: it's technically a Schefflera now, so the name is the much less musical Schefflera elegantissima.
5 I forget whose original point this was; someone mentioned it in the comments here a long time ago, and I agree, so it stuck with me. I just can't remember who said it originally, for which I apologize.
6 (Not that crying babies aren't lovely.)
7 (It's usually a he.)
8 How Plants Get Their Names, Dover Publications, Inc., Mineola, NY, 1963, p. 115. This edition is an unabridged reprint of a work initially published in 1933, which is why it sounds all literate and crap.
9 Though it does get to be a lot to expect in situations like mine, where I'm expected to know not only the names for the 250-300 species of plant we have in the greenhouse, but then also another 50-100 annuals, maybe 150-250 perennials, and unknown numbers of shrubs and trees. I'm learning as fast as I can, but I still need to look at the tags, or ask people, on the more outdoorsy stuff.