(Editor's Note: This article was originally published on March 5, 2008)
From classical latin to medieval low Latin comes botanical Latin. Scholars and academics have discussed the forms of Latin and suitability of many, many Latin words and phrases for centuries. In the mid 18th century, Latin had already evolved from the classical Latin of Roman scholars to the Medieval Latin of academia, politics and ecclesiastical use. It was even further refined to a form that suited the descriptions required in the study of botany. The ancient language of early Greece played an important role in shaping many of the words as botanists searched for adjectives and words that resulted in greater precision and accuracy. William T. stearn describes Botanical Latin ".... as a modern Romance language of special technical application, derived from Renaissance Latin with much plundering of ancient Greek...."  Today, we still discuss the correct pronunciation and usage of Latin as it continues to be the subject of debate. In addition to the influences of the Greek and Roman languages on botanical Latin; other less known but certainly noteworthy influences have included the languages of Germany, Holland, the Middle East and the Orient.
Latin should have been on my course list in high school and would have been had I known I was destined for a career in horticulture! For a thorough understanding of how Latin is used throughout botanical nomenclature, and the language of science in general-one needs to have an understanding of the structure of the Latin language and its appropriate rules of grammar. It is a language filled with prefixes and suffixes, declensions, gender, number and case agreements, stems and roots. It is because of these grammatical policies that we have rubrum and rubra! For many of us, the mysteries of Latin will likely remain so. There are however many excellent reference books available for gardeners curious to know more. Several by William T. Stearn (described as the modern day Linnaeus) are available and I have used these in my research.
The binomial system became the standard in the mid 18th century and changed the way scientists, naturalists and students of botany and zoology would name and classify plants, fungi and animals. This methodology was adapted and popularized by the Swedish physician and botanist, Carolus Linnaeus in the mid-1730s and published in several important works including Systema naturae (1735) and Philisopha botanica (1751). The binomial system adapted to botany, replaced the complex naming format that was in place at that time which included lenghtly descriptions in Latin and borrowed words from the Greek language. Essentially, the binomial system involves the use of two principle words to denote the name of an organism. The first word is the genus for example Achillea. The second word is the specific epithet for example millefolium. The correct form to write these words is to italicize both words but only capitalize the first word-Achillea millefolium. Sometimes the words are underlined rather than italicized-Achillea millefolium. This is acceptable too-but don't underline and italicize at the same time.
Geographical place names, habitat and famous people both real and mythological are just some of the many variables which influence the binomial naming of plants. Plants indigenous to certain geographical regions of eastern North America or the orient may be named with specific epithets such as canadensis, pennsylvanica, japonica or chinensis. Habitat is an important influence on plant names. Consider arvensis as in Mentha arvensis, Veronica arvensis or Sonchus arvensis--Stearn notes that arvensis refers to "Growing in or pertaining to cultivated fields."  Some familiar specific epithets include fortunei, x jackmanii and davidii and are so named after notable figures in the horticultural world. The genera Abelia, Forsythia and Zinnia pay tribute to notable botanists while Narcissus comes from classical Greek mythology.
Perhaps the greatest contribution to plant names comes from the vast collective of characteristics of plants themselves. The morphology of plants including its flower parts, fruits, seeds, reproductive organs, roots and stems, shape of leaves, margins and form are describe in a myriad of ways. Colour, shape, texture, margins hairy, smooth, upright, creeping and twining are all expressed in words whose origins may be Greek, Roman, Germanic and so on. In fact during the 19th century, naturalists and botanists who were successors of Linnaeus focused extensively on the descriptive terms of plants based on their shape, organs and attributes. Take for example the ornamental grass Calamagrostis acutiflora. This can be broken down as follows: Calam (reed-like), agrostis (a kind of grass), and acu (sharp) and flora (flower). Once you start to learn some of the more common words and stems you will observe how they repeat themselves. Without knowing too much Latin one can deduce that words like floriferous, floribunda, and floridus relate to the flower. Folium, foliage and foliaceus are referring to the leaves of a plant, for example Trifolium pratense (trifolium=having three leaves.)
Today, the International Code of Botanical Nomenclature (ICBN) determines the guidelines for new plant names. The ICBN (governed by the International Botanical Congress and the International Association for Plant Taxonomy) has determined that the formal start point of our current system of botanical nomenclature (system of naming things within a larger group) coincides with the publication of Linnaeus' Species plantarum on May 1, 1753.  Today's plant naming is a little different than in Linnaeus' day because of the thousands of cultivars that are available and continue to be developed. Cultivars are generally vernacular or fancy names rather than Latin and are not italicized but are enclosed in single quotation marks for example 'Goldstrum'. The naming of cultivars is also regulated and under the direction of the International Code of Nomenclature of Cultivated Plants. Additionally, the naming of new species does not have to have its origins in Latin (as was deemed mandatory by Linnaeus in his time), although the International Code does recommend botanists "....to use Latin terminations in so far as possible...." 
Communication in horticulture often relies on using the botanical names for plants to ensure accuracy. Imagine a discussion about Moon Flowers without the accuracy afforded by using botanical names. Do you mean Ipomea or Datura? Each plant species has its individual binomial that is unique to that genus and specific epithet. Botanical Latin transcends language barriers and is truly a universal language for horticulturist, botanists, naturalists and of course gardeners. While understanding the taxonomy of plants and the history of their nomenclature may not be imperative to rewarding gardening; it does provide one with an historical connection to some of the great pioneers in the field of botany and horticulture and the complexities of ancient languages.
 Stearn, William T. Botanical Latin 4th Edition. Portland: Timber Press, Inc. 2007
 "Carolus Linnaeus," Microsoft Encarta Online Encyclopedia 2007 accessed from the World Wide Web January 9, 2008
 Stearn, William T. Stearn's Dictionary of Plant Names for Gardeners. Portland: Timber Press, Inc. 2002
 ibid 
 ibid 
 Wikipedia article on International Code of Botanical Nomenclature, accessed from the World Wide Web January 9, 2008
photo credit: http://www.boekendingen.nl/wp-nieuws/?p=854