I recently learned that the pineapple guava tree, formerly known as Feijoa sellowiana, is now going by Acca sellowiana.
This sort of re-naming, while confusing, isn't uncommon: Stipa tenuissima is now Nassella, Diosma pulchrum is now Coleonema, Atriplex spinosa is now Grayia, Laurentia fluviatilis is synonymous with Isotoma fluviatilis is synonymous with Pratia pedunculata, and so on. Which begs the question, if these supposedly sacrosanct botanical names can be so fluid, why do they matter?
It helps to understand the difference between botanical, or "scientific," names and common, or "vernacular," ones. While common names such as "pineapple guava," "breath of heaven," and "blue star creeper" roll easily off the tongue (and offer ample opportunity for seductive descriptions in mail-order catalogs) they are imprecise, usually relying on associations not obvious to everyone. What is a "lily of the valley" to you? An herbaceous perennial, or an evergreen shrub? For some real entertainment, peruse Wikipedia's list of plants by common name: not only can you see why ordering a "white birch" could get you into trouble, but you'll also see that a brown daisy, yellow daisy, black-eyed Susan, and brown-eyed Susan are all the same plant, depending somewhat arbitrarily on where in the U.S. you live.
Botanical names, on the other hand, are determined systematically rather than arbitrarily, and are consistent throughout the world. Every species has one, and only one, botanical name; and that name describes not only its unique characteristics but also its relation to other species. This system was developed by the premier 18th-century naturalist Carl Linnaeus, who classified all living things hierarchically by their common characteristics rather than, say, geographic origin. In botany, we are usually most concerned with the genus and species names; less frequently with the larger family or the smaller subspecies and/or varietal names. So our old favorite the black-eyed Susan can most accurately be described as Rudbeckia hirta — that's genus Rudbeckia, species hirta, which tells us it's related to yet different from Rudbeckia fulgida and Rudbeckia laciniata. (Now we only need to decide whether we mean the variety R. hirta var. angustifolia, or R. hirta var. pulcherrima.)
Seems pretty straightforward, right? Well, not quite. In a future post, I'll talk a bit about the "Deep Green" project spearheaded by Brent Mishler at Berkeley, which aims to trace plants' evolutionary paths and reclassify them in a cladistic, not Linnaean, manner — meaning that the venerable Zea mays would be renamed Mays Zea Gramineae Monocots Angiosperms Eukaryota Life. Not quite as poetic, perhaps, but technically more accurate… and definitely more precise than "corn."