Pelargoniums: An Herb Society of America Guide

Taxonomy

Illustration of Pelargonium graveolens from L'Héritier's Geraniologia (1787-1788)

Confusion has surrounded Pelargonium nomenclature since the dawn of taxonomic classification and continues to this day. The common name geranium is associated with hardy North American and European plants from the genus Geranium as well as tender South African plants from the genus Pelargonium due to a very early misclassification of the genus. The plants were originally classed in the genus Geranium by Linnaeus in 1753 (15), along with plants that are now known to be in the genera Geranium and Erodium, both members of the family Geraniaceae. Although the French botanist Charles L'Héritier first classified pelargoniums as a separate genus in the late 1700s, this nomenclature was not widely accepted until many years later (15), long after the common name geranium had become irrevocably associated with pelargoniums.

Pelargonium nomenclature confusion doesn’t end here. To complicate matters further, the parentage of many Pelargonium cultivars is uncertain (90), and there are many identical plants that may appear under several different names in the trade (6, 90). Conversely, some plants bearing the name of historic cultivars are actually different plants (15). Genetic testing has shed new light on Pelargonium classification, and will probably continue to do so. For example, most plants sold in the U.S. and Europe as P. graveolens, are now believed to actually be a group of hybrid cultivars due to differences in chromosome numbers and pollen fertility (88).

The genus Pelargonium is divided into 14 sections, which are used to organize the various species. The majority of the scented-leafed species belong to sections Pelargonium and 
Reniformia, with some scented-leaf species occurring in Cortusina, Jenkinsonia, Ligularia, Peristera (63) and Ciconium (5).

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