Synonyms for Genus Names

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In English, the name of a thing is a synonym if that thing also has another name, i.e., two names referring to the same thing are synonyms.  Each name refers to the other and can be freely substituted.

In the world of botanical names, each name is required to be unique and refer to a single thing.  If you are the first to discover a plant, you will give the plant an appropriate name.  Subsequently, others may think that they have discovered a new plant, and each of them will give their new plant a suitable name.  What happens, after the dust clears and it is discovered that all of these plants are in fact, the same plant?  According to the International Society on Botanical Nomenclature, the first given name should take precedence, the other names are rejected, and thereafter referred to as synonyms.  So a synonym, in plant names, is not like a synonym in our common language. In this context, a synonym is an illegitimate name, a name which has been rejected, and one which is not to be used, henceforth.  "After the dust clears" is my term for the considerable number of years which may have passed before the determination of the "preferred name".  In the meanwhile, the use of the synonym may continue unabated for decades until the information filters all the way down to the backyard gardener like you and me.

Perhaps, you purchased a new plant reference guide, and suddenly discover that some of the plants you know by one name should really be called by another name.  That takes time.  Until recently, the garden reference work on my desk had been printed in 1960.  At the same time, you may do a search on a plant name in books or on the world wide web, and find no references at all to your keyword because you are unknowingly searching on a synonym.  

The pages presented here list 10,608 synonyms for genus names, followed by the preferred genus name, family to which it belongs, and type of plant.  Whenever your search on a genus comes up blank, try here to see if there is a preferred name which will greatly increase the odds on your finding useful information.  The source of this information is 'The Plant Names Project (1999). International Plant Names Index.  Published on the Internet: (accessed 15 December 1999)'

IPNI is the product of a collaboration between The Royal Botanic Gardens, Kew, The Harvard University Herbaria,  and the Australian National Herbarium

Is this the final authority?  The first and foremost problem of all plant name indexes lies in their being outdated  before the material even reaches the printing press.  As time passes, they become less and less accurate.  At the same time, there are many disagreements about plant names, and the authors of the indexes have to make a choice in favor of one name or the other.  Who knows which name will later become the synonym?  Here are a few examples:

The RHS "Shorter Dictionary of Gardening", 1998 implies that Dolichos is a synonym of Lablab, while IPNI indicates that these are separate genera.

The RHS implies that Coleus is a synonym of Solenostemon, while IPNI says that Coleus is actually a synonym for Plectranthus, and that Solenostemon is a separate genus.

Hortus III implies that Fallopia is a synonym for Reynoutria, while IPNI says that Reynoutria is a synonym for Fallopia.

According to the International Code of Botanical Nomenclature (International Association for Plant Taxonomy, Utrecht, 1992) the names of plant families must end in -aceae. However, eight plant families are exceptions in that each has two alternative names, both of which are correct under the Botanical Code. One is a standard name, ending in -aceae, the other is an exception, sanctioned by long usage. These and their alternatives are the following:

Standard family name/Traditional family name









Poaceae Gramineae
Fabaceae Leguminosae
Apiaceae Umbelliferae
Asteraceae Compositae

What do these differences of opinion mean to the backyard gardener, and who does one believe when using a plant name? This is what I recommend.  First, consider that the most recent published authority is always correct.......................for the moment.  You cannot simply adopt one Genus name, and force all other towards your point of view.  There are often legitimate arguments in favor of one name or the other. On-line materials such as IPNI will be updated more often than printed materials, and is the joint effort of competing authorities, therefore the accuracy of this data will be continuously maintained (but not necessarily correct.)  Second, where differences in opinion in plant naming become apparent, even at our level, come back to the IPNI site and use their preferred name. Finally, I suggest that you replace your desk reference at least every five years.  Get in the habit of recognizing and avoiding the use of synonyms, unless it is absolutely necessary that you be correct, in which case you are doomed to a life of confusion.

p.s.  My definition of synonym is not universally recognized.  Either all names for a given plant can be used name is to be preferred above all others in the sake of accurate communication.  What do you prefer?  The IPNI site makes the disclaimer that it is not a naming authority and that its function is merely to list all of the given names.

Disclaimer #1: "All or some species names have been transferred to the genus listed, and sometimes split into two or several genera. Please check that this also applies to your particular species."  In other words, some of the data presented is always correct, and some of the data will never be correct, and the remainder could be leaning in either direction.

Disclaimer #2: "The use of the term "preferred name" is shorthand for the phrase: "commonly accepted name, but not necessarily the correct name."

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