Why do all the plants have Latin names?

Why Latin?

From ancient times until about a century ago, Latin was the universal language of scholarship. The main reasons for this were, first, the Romans left behind quite a scholarly library, it was all written in Latin, and the remaining European peoples didn't start adding substantially to that library until hundreds of years after the fall of the Roman Empire. Moreover, during that time, the Christian Church was the primary custodian of scholarly literature, and they spoke Latin. Consequently all scholars had to learn Latin, and indeed, most of the scholarly works of botany continued to be written in Latin down into the 19th century. Descriptions of new species were required to be written in Latin until 2012, so until quite recently Latin remained the predominant language of botany. This Latin tradition was finally upended by the British Empire and the USA, which have made English the first language over much of the world, as well as the universal language of international trade and commerce; this largesse has overflowed into science and the arts, such that English has now replaced Latin as the universal language, spoken as either first or second language by over two billion people, for most of whom it is not their native tongue.

The fact remains that for over 2,000 years, Latin was the primary language of botany, and during that time (and especially since about 1750), botanists have assembled a strict formal system of names such that every scientific name has its place on the tree of life, and those names when taken together describe how all living things are related to each other. Since it would be tedious to tie every name back to the root of the tree whenever speaking it, scientific names are usually limited to two words, showing the species and the first step back to the root, which is the genus. There are also six more steps: the family, order, class, phylum, kingdom, and division. The first word in a typical scientific name denotes the genus and is the "generic" name; the second word is the species and is called the "specific epithet"; if there is a third word, it denotes a subspecies or varietal name. These names are not only to map out the tree of life, but also because in order to discuss an organism in detail, we must be able to name it, and knowledge about the details of one organism can often be used to understand related organisms. (by the way, this scientific fascination with names has a certain relationship to magic, and is one place where science and magic come rather close to each other). So, we hold on to Latin for this one reason: to describe the tree of life.

Pronouncing Latin Names

First, and most importantly, it does not really matter. Botanical Latin is not spoken Latin and does not derive from any spoken Latin, e.g. liturgical Latin or reconstructed Roman Latin. I have been to international scientific meetings where prominent scientists from all over the globe come together, and they pronounce Latin names in such widely varying ways that I sometimes have to ask for the spelling in order to know what plant they are referring to. These differences don't bother them and should not bother you.

There are basically only two rules for correctly pronouncing botanical Latin names: pronounce the word roots as in the original language, and pronounce the word endings as in liturgical spoken Latin.

It can be difficult to find out how to pronounce the word roots. The most common root names are taken from Latin itself. Latin survives in the modern world through the Romance languages, including French, Italian and Spanish. If a word is similarly pronounced in those languages, that will show how to pronounce the Latin root. Pinus, for example, is pin in French and pino in both Italian and Spanish, all of which are pronounced "peen". Cedrus is taken from a Greek root, Κέδρος, and is pronounced with hard "C", as if it were "K". This is an example of a botanical name that is usually mispronounced by English speakers, though Greeks get it right. The epithet of Picea likiangensis is based on the city of Lijiang 丽江 in China, and should be pronounced as the Chinese pronounce it; the peculiar spelling reflects the form of phonetic spelling that Europeans used for Chinese words when the species was named in 1899. Sometimes roots are compound; in Ephedra antisyphylitica, for instance, "anti" is a Latin root that denotes "the opposite", and "syphylitica" refers to syphylis, so the name literally translates as "Ephedra that opposes syphylis" (but not very effectively, by the way). Sometimes this can get pretty complicated: in the epithet of Dacrydium araucarioides, "araucar" refers to the conifer genus Araucaria, the name of which is derived from the province of Arauco in Chile, a word that is a name in a local Indian language (good luck finding out how that is pronounced). The ending -ioides means "resembling", so the name literally translates as "Dacrydium that resembles an Araucaria".

The ending of likiangensis is -ensis. Latin is a language that conjugates its nouns, and this ending denotes possession, so that Picea likiangensis literally translates as "spruce of Lijiang". Latin nouns also fall into 3 declensions, so there are about 20 standard possible endings for names. In general any standard phonetic pronunciation is acceptable. If you want to do better, listen to some liturgical Latin. Note that when a word ends in "ii" the second "i" is a separate syllable, and when a word ends in 3 vowels, the second two form a separate syllable.