Plant Names

What’s in a Plant Name?

Most plants we use in the landscape have both a common name and a scientific or latin name.

Common names:

Helenium autumnale is Common Sneezeweed in North America but not in Australia where another plant goes by that common name

The common name is just that - the name of the plant in common usage. This can sometimes be used to identify a plant but it is often not a unique identifier. For example there are are several plants that are called “Black-Eyed-Susan” if you specify Black-eyed-susan on a project plant list you might get what you want - then again you might not. 

Common names are further complicated, in that, the same plant may be referenced by several common names and different common names may be used in different parts of the country or world. Sneezeweed for example refers to various North
American species in the genus Helenium, but in Australia Centipeda cunninghamii is called common sneezeweed. The common garden annual Celosia argentea is used as a food crop in Africa and has many common names including Celosia, Lagos spinach, soko, quail grass, cocks comb, and mfungu to name a few. 

While it is useful to know the common name of a plant, plant professionals will always back up the use of a common name with the scientific name.

Scientific names (Latin names):

Sedum spurium is now called Phedimus spurius in some references. Although the name might change officially most suppliers and many references still list the plant as a sedum and may not even know what you are after if you call it by the name Phedimus

Scientific names are, at least in theory, unique identifiers for a plant that will be understood no matter where you are, and should result in your obtaining the desired specimen when you specify a plant using this name. 

In the past once you learned the scientific name of a plant it would seldom change. That is no longer true. Plants used to be classified and grouped based on their appearance, so plants with similar flower structures for example would be considered to be related and be grouped in the same family, and if they were similar enough, the same genus or species. Once classified there was little reason or logic in changing the name so things were pretty stable in the plant nomenclature world for several hundred years.  

You are fortunate, or maybe not in this case, to live in the age of genetic mapping. This has resulted in the re-examination of the relationships of one plant to another using genes rather than morphological characteristics. In the long run this will be a good thing, but in the short term what it means is that the name you learn this year may not be the name in the future. Changes in Family relationships are starting to settle down now and probably will not change too much more in the future but Genus and Species... expect a lot of changes as additional research is conducted. 

Chrysanthemum x morifolium Ramat. was Chrysanthemum morifolium when I was an undergrad. When I was in graduate school the name changed to Dendranthema grandiflorum but now as you can see it has changed back.

Parts of a scientific name of a plant:

The scientific names of plants follow a naming convention developed by the Swedish botanist Karl von Linne - or Carolus Linnaeus. The system is known as binomial nomenclature where each plant is given a two part name, Genus and species. 

The genus is always capitalized and the species is always lowercase. 

When written, the scientific name should either be in italics or underlined. 

In the scientific or botanical literature the species name is followed by the surname of the authority (the person who named the plant). Since Linnaeus named many plants, many scientific names are followed by an L. For example Salvia officinalis L. is the scientific name for culinary or kitchen sage. 

Pelargonium x hortorum is the common garden or zonal geranium. The (x) in the scientific name indicates that it is a hybrid.

An x in the scientific name between genus and species indicates that the plant is a hybrid. For example Pelargonium x hortorum L.H. Bailey (pro sp.) [inquinans x zonale] indicates that the ‘zonal geranium’ is a hybrid between P. inquinans and P. zonale made by L.H. Bailey. 

Note that in the preceding sentence the genus Pelargonium was shortened to just the first letter. This is commonly done when referring to multiple species of a genus where the genus will be listed the first time and just the first letter will be used thereafter. 

The genus and species can also be followed by a subspecies designation (subsp.) or a botanical variety designation (var.). 

In some cases where a species can not be identified (sp.) will be used to designate a single unknown species and (spp.) is used to designate multiple unknown species. So Eupatorium sp. indicates that the plant is an unknown Eupatorium species and Eupatorium spp. means that you are referring to 2 or more species in the genus Eupatorium.

An x in front of the genus indicates that the plant is a hybrid between 2 genera. This is relatively rare since few intergeneric hybrids are viable. One example we are studying this semester is x Heucherella an intergeneric cross between Heuchera and Tiarella. Sometimes people leave out the x’s, particularly with intergeneric crosses like Heucherella.

Cultivar names and trade names:

Many of the plants we use in ornamental horticulture are specific cultivars. A cultivar is a “CULTIvated VARiety”. 

A cultivar will have unique characteristics that distinguish the plant from others in the species. 

Hemerocallis ‘Stella de Oro’ is a commonly used daylilly cultivar.

Common distinguishing characteristics for cultivars are flower color, plant form, flowering time and leaf characteristics. 

For example one of the most commonly used daylilies in the landscape is Hemerocallis ‘Stella de Oro’

The standard naming convention in the trade is the genus and sometimes the species, if known, followed by the cultivar name in single parentheses. 

‘Stella de Oro’ has golden yellow flowers, is a compact plant, and a repeat bloomer, all of which make it a better landscape plant choice than an unselected random Hemerocallis seedling.

In the trade plants are often specified using just the Genus and a cultivar name. For example if you wanted to plant yellow tulips you might specify Tulip ‘Golden Apeldoorn’ which is a fairly common Darwin Hybrid tulip.

The plant called Bacopa in the trade is actually in the genus Sutera not the genus Bacopa.

Names used in the industry are not always correct. For example the trailing basket plant called Bacopa is not really in the genus Bacopa, but is actually in the genus Sutera. It was likely mis-identified or mis-labeled when it was first imported and the incorrect name stuck.

What do the names mean and how are they chosen?

The scientific name is generally Latin or Greek or something meant to sound like Latin or Greek. 

Acanthus spinosis has spiny thistle-like leaves, hence the species name.

The species name is sometimes derived from the name of the authority who named it, one of their relatives, friends, etc. For example Gaura lindheimeri is named for Ferdinand Lindheimer a botanist who lived and worked in Texas in the 1800’s.

The species name often comes from a characteristic of the plant. For example Acanthus spinosis (Spiny Bears Breeches) is a plant in the genus Acanthus with spiny leaves. 

The species name may also be derived from the native range of the plant or the place where it was discovered, for example Echinacea tennesseensis. 

Pot marigold, Calendula officinalis was used in Europe as a food crop and medicinal herb. It is still used today as a medicinal herb.

Another common specific epithet is officinalis which generally refers to the official medicinal form of the species usually named by Linnaeus, for example Calendula officinalis.

Plant name resources:

Although books can be useful to confirm plant names, with the rate of change in Botanical nomenclature a reliable web based resource is frequently more up to date. 

For this class we will use several sources for scientific names. The USDA plants database will be the primary authoritative source for this class. This is a pretty good source and is also useful to confirm native, or adapted status of a plant along with information on invasiveness. The USDA database is however, not always up to date with name changes. 

A second source which is often more up to date for our landscape plants and also contains some cultivar information is Missouri Botanical Garden “plantflinder”. 

A third resource we will use is the RHS PlantFinder. This is also usually up to date. 

In addition you can also use the Kew gardens website. 

By using multiple resources and comparing and confirming names we can, with a little luck, be using the current name for a plant. In some cases for the purposes of this class both the current and former name may be acceptable depending on what name is more commonly being used in the trade.

Sedum reflexum ‘Blue spruce’ and Sedum spurium ‘Dragons blood’

Plant name exercise:

Answer the following using the assignment in the Canvas week 1 module

Using the three online resources below look up Sedum rupestre. What is the proper name for this plant according to each source? What name would you use to specify this plant for a green roof plant list?

USDA Plants database

Missouri Botanical Garden Plant finder

RHS PlantFinder

© Penn State Horticulture  2021