Many clients of my landscape design practice have difficulties with the botanical names of plants. Generally, I specify both botanical names as well as English names of the plants included in planting plans, but that is not always possible since many plants are only known by their scientific names. Literature about plants, plant labels in garden shops, and gardening sites on the internet, all use Latin names for plants to some degree. What follows is a brief guide to these names, their origins, meaning and purpose, helping you to make sense of the botanical naming system.
A few centuries ago, botanical names of plants were really Latin descriptions. As the number of identified plants grew, these descriptive sentences had to become longer to distinguish newly discovered plants from existing ones. The Swedish botanist Linnaeus (1707-1778) was the first to consistently use a much simpler system, binomial nomenclature, in which each plant was given a botanical name consisting of two words.
The first word of a botanical name is the genus, and is a bit like our surname, relating to a group. The second word is the specific epithet, referring to a particular species within that genus. It is similar to our first name in that it may occur in many different genera. For example, Coprosma acerosa is the botanical name for the sand coprosma, a ground-covering plant with tiny leaves and interlacing branches. Coprosma repens (taupata, mirror plant) on the other hand, is an evergreen shrub or tree growing to about 6 m tall.
Coprosma acerosa Coprosma repens
Pyrus communis is the name of the European pear, the precursor of most modern pear cultivars. Another species in the same genus is Pyrus salicifolia, the willow-leafed pear, which produces small pear-like fruit that are virtually inedible. The specific epithet salicifolia is used for a number of different unrelated plants such as Hebe salicifolia, Baccharis salicifolia (mule fat), and Hakea salicifolia.
Both the genus name and the specific epithet are normally written in italics, with the first word beginning with a capital letter.
You may find that the botanical name is followed by an abbreviation, for example Pyrus salicifolia Pall.. This particular abbreviation refers to Peter Simon von Pallas, a German zoologist and botanist who was the author, i.e. the first person to publish a valid, accepted name for the plant in question. Another, more common abbreviation is L., referring to Linnaeus who was the author for a large number of plant species.
Botanical names versus common names
Botanical names allow us to communicate about plants with other people all over the world. Common names are widely used also, but they have a number of disadvantages:
1. Common names are words in the language of the country or region where they developed as accepted terms for a particular plant. For example, Pyrus salicifolia 'Pendula' is known as weeping silver pear in English speaking countries, but as treurpeer in the Netherlands.
2. Many plants are known by more than one common name, or conversely, one common name may be used for completely different plant species. For example, the common name pepper tree may refer to Schinus molle, or to one of two unrelated New Zealand species Macropiper excelsum and Pseudowintera colorata.
3. Some plants have no common names. People develop words for plants they see or use, so plants that are rare or not particularly useful for some reason, may not be known by a common name.
4. Some common names seem to allude to a particular plant characteristic, but are in fact misleading. Solanum pseudocapsicum is commonly known as the winter cherry, but produces poisonous fruit.
5. Common names are not organised by any official code, whereas scientific names are goverened by a set of formalised rules called the International Code of Botanical Nomenclature.
In short: two plants with an identical botanical name belong to the same botanical group, but two plants with the same common name may belong to completely different and unrelated botanical groups.
A multiplication sign between the generic name and the specific epithet (e.g. Cestrum x cultum) indicates that you are dealing with a hybrid. That means the plant originated from a cross between different species within the same genus. An 'x' in preceding the botanical name means that the hybrid is the result of a cross between different genera. This is not very common since genera are usually too different genetically to be crossed, but there are a few in existence, such as x Heucherella tiarelloides which is considered to have originated from a cross between Heuchera and Tiarella.
Instead of simply a new name that includes a multiplication sign, hybrids may also be specified by a formula consisting of the names of the parent species separated by an 'x'.
The term cultivar refers to a group of plants that have been selected for a particular characteristic or combination of characteristics, are distinct from any other plant in cultivation, and are stable in those characteristics when propagated. For example, the weeping habit of Pyrus salicifolia 'Pendula' distinguishes this cultivar from its parent, Pyrus salicifolia. Similarly, the specific yellow and green colorations in the leaves of Elaeagnus pungens 'Maculata' give this plant a very different appearance from the green-leafed Elaeagnus pungens.
Elaeagnus pungens 'Maculata'
Cultivars are specified by a botanical name (of a species, or, in case of a hybrid cultivar, of a genus) followed by a non-italicised, capitalised cultivar epithet enclosed by single quotation marks.
Cultivar names by themselves are not very useful. The cultivar epithet 'Alba' has often been used to name a white-flowering cultivar of a particular species. It could refer to a cultivar of Daphne odora, Amaryllis belladonna, and many other species.
A variety is similar to a cultivar, but rather than resulting from selection in cultivation, varieties originate in the wild. Hence the term often refers to a group of plants of a particular species in a specific geographic area that is distinctly different from plants of that same species in other areas. Examples are Buxus microphylla var. koreana from Korea and Buxus microphylla var. japonica from Japan. They are sufficiently different from each other and from Buxus microphylla (small-leafed box) to warrant unique names.
Unlike synonyms in other contexts, botanical synonyms are not interchangeable with the botanical names for which they are synonyms. They are old, obsolete names, originally published for particular plants, but superseded by other scientific names. Synonyms may come about in one of two ways. Firstly, one and the same plant species (or genus) may have been named more than once independently, in which case the oldest name becomes the official scientific name. Secondly, plants may have originally been placed incorrectly within a certain botanical group, e.g. the wrong species or genus, and later moved to the correct group and given a new name accordingly. Because scientists nowadays have a much wider range of plant identification techniques available to them in addition to the traditional morphological methods, such changes are still occurring. Old names are retained as synonyms since texts written prior to the name change will still refer to these. If you wish to learn something about a plant that happens to have a synonym, and you cannot find any relevant information about this plant when searching for its currently accepted name, you could try searching for its synonym.
Botanical names translated
Botanical names of plants, in particular the specific epithets, are often descriptive in some way.
They may refer to the leaf or flower colour, such as:
alba = white
argentea = silver
aurea = gold, yellow
flava = yellow
glauca = blue
purpurea = purple
rubra = red
variegata = variegated (more than one colour)
virens, viridis = green
They may refer to the shape or growth habit, such as:
pendula = weeping
procumbens = creeping
prostrata = prostrate
scandens = climbing
They may refer to the country, region, or habitat of origin, such as:
canadensis = from Canada
chilensis = from Chile
japonica = from Japan
maritima = from near the sea
sibirica = from Siberia
sinensis = from China
They may refer to textures, such as:
barbata = hairy
glabra = shiny
hirsuta = hairy
hispida = bristly
lanata = woolly
spinosa = spiny
villosa = hairy
They may refer to a person, such as:
Banksia: named after Sir Joseph Banks (1743-1820), English naturalist and botanist
Rosa banksiae: named after Lady Banks, wife of Sir Joseph Banks
Camellia: named after Georg Joseph Camel (1661-1706), also known as Camellus, Jesuit missionary and botanist to the Philippines
Magnolia: named after Pierre Magnol (1638-1715), French botanist
These lists are by no means complete, but they show that the Latin words that make up botanical names were originally chosen for a reason.
If you are interested in learning more about plant names, then I can recommend a great little reference book by A.T. Johnson and H.A. Smith, entitled "Plant names simplified - their pronunciation, derivation and meaning". This is like a dictionary with plant names organised by genus, followed by specific epithets associated with that genus. Entries include the phonetic spelling for each word and its translation(s). The authors explain where the names are derived from, or whom the plants were named after. Some genera entries are followed by a very brief overview of the types of plants included. The book has been revised, updated and reprinted many times.