How To Name Plants Correctly – Botanical Names vs Common Names

Knowledge of plant names is the foundation of gardening and they help gardeners select plants and determine how to grow them. Many gardeners obtain or share knowledge by communicating with other plant enthusiasts from around the world. A good grasp of plant names and how to use them, will save you significant time, effort, and money.

The proper use of plant names becomes more complicated when we consider varieties, cultivars, hybrids, and regional differences between common names.

A rose by any other name might not smell as sweet…because it’s an entirely different plant!

Why Are Plant Names Important?

You are on social media and someone posts a picture of a hen and chick and asks if the plant is hardy in zone 5. Some people say yes and others say no. Clearly, everyone can’t be right. The reason some of this advice is wrong is that a common name was used instead of a proper scientific name.

The above image shows two plants that go by the common name “hens and chicks’. The left is Echeveria elegans and the right is Sempervivum tectorum. They share some similarities but look different, have different flowering habits and life cycles. The one on the left is not hardy in zone 5, while the one on the right is. As long as people use the common term hens and chicks, it is difficult to get the correct cultural information.

Binomial Naming Conventions

Plants can either have a common name and a botanical name, multiple common names and a botanical name, or a botanical name but no common name (or at least not one that is widely used). Sometimes, different plants share the same common name, but the botanical name is unique to only one species. Botanical names are also called scientific names or binomial names.

The common name is simply the name that caught on in a certain area over time. In contrast, the scientific name corresponds to a precise, universal system – the International Code of Botanical Nomenclature, developed by 18^th century botanist Carl Linnaeus. The binomial name consists of two italicized words, the first corresponds to the plant’s genus and the second to the species. A genus is a grouping of species with similar characteristics, whereas a species is made up of individuals that share the same traits, and can sexually reproduce with each other to make viable (i.e. fertile) offspring.

For example, Cercis canadensis is the botanical name for the Eastern redbud, also known as the American redbud.

Only the genus name is capitalized when using the binomial system. Words in the common name are generally not capitalized unless it is a proper noun, but sometimes capitals are used as a stylistic choice.

How are Hybrids Named?

Primary hybrids are a cross between two different species (interspecific hybrids). Plant hybrids occur in nature, but are also produced by intentional crossbreeding for desirable traits.

There are two ways to name hybrid plants using the binomial naming system. Firstly, if the hybrid is well-known enough to have been given a specific name, then the name will be the genus, followed by ‘x’, and the hybrid name. For example, Acer x freemanii is the binomial name of the Freeman maple, a naturally occurring cross between Acer saccharinum and Acer rubrum. The ‘x’ tells you that ‘freemanii‘ is a primary hybrid and not a species. This hybrid could also be called Acer rubrum x saccharinum.

Hybrids can also occur at the genus level and are then called intergeneric hybrids. These hybrids are usually intentional, sterile and must be propagated vegetatively. Leyland cypress, x Cupressus leylandii (or Cupressus x leylandii), is a cross between Cupressus nootkatensis and Hesperocyparis macrocarpa.

It is common to name an intergeneric hybrid after a combination of the two genera names, such as with Sorbaronia shrubs, which are hybrids between Sorbus and Aronia, and formally called x Sorbaronia. A hybrid between Aronia melanocarpa (black chokeberry) and Sorbus aucuparia (mountain ash) is called x Sorbaronia mitschurinii or just Sorbaronia mitschurinii. Common cultivars of this hybrid include ‘Viking’ and ‘Nero’

Naming Varieties and Cultivars

It’s common for gardeners to use the terms “variety” and “cultivar” interchangeably but these terms mean different things and they have different naming conventions.

The main difference between a cultivar and a variety is that a variety will produce seedlings with the same traits as the parents, whereas cultivars do not retain their traits unless they are propagated vegetatively (cuttings, grafting, and or tissue culture). Most plants sold in the horticultural trade are cultivars.

To give an example, Cercis canadensis var. alba is the name given to a variety of Eastern redbud with white flowers. Subsequent generations will likely also have white flowers, provided both parents had white flowers. Note that the name follows an abbreviation for variety, i.e. “var.”, and the variety name is in italics.

Cultivars, on the other hand, are named with the cultivar name after the botanical name in single quotations, such as with Cercis canadensis ‘Appalachian Red’. The cultivar name is not italicized. The common name would be Appalachian Red Eastern redbud and all such trees are likely clones from one original plant.

Lastly, it is also possible to produce cultivars from varieties. In that case, the botanical name would be the variety name followed by the cultivar name in single quotations, such as Cercis canadensis var. alba ‘Royal White’.

Knowing the correct name of the plant provides you with important information about how to propagate it to maintain it’s genetic purity. Varieties can be propagated either from seed or vegetatively. Cultivars can only be reproduced vegetatively.

Changes to Scientific Names

Plant names are not carved in stone. As new information becomes available, scientists re-evaluate the status of plants and occasionally rename them. In recent years, genetic testing has made this a frequent event. This was the case for the New England aster, Symphyotrichum novae-angliae, which was changed from Asteraceae novae-angliae, after it was discovered that it’s not related to the aster family despite the similar flower shape. Adding to the confusion is the plants’ tendency to produce hybrids or develop new traits through mutations. This brings further complications to naming plants.

Why Use the Correct Plant Name?

You may have noticed that gardeners who have several years of experience or formal training, tend to refer to plants by their botanical names. Newer gardeners, or gardeners who take a less technical approach, often refer to plants by their common names.

Common names sound interesting and may be easier to remember. It can be quite fun to compare different regional common names and dive into their origins. However, common names are completely unregulated so there’s a good chance that another person will assume you are referring to a completely different plant. That problem is eliminated when you us a proper name. Using a plant’s scientific name also increases the odds that the plant you are buying is the one you really want.

A good example of a confusing common name is the “outhouse plant”  or “outhouse flower”. Before the days of indoor plumbing, tall flowers were grown around outhouses to disguise their look and smell from visitors. Rudbeckia laciniata ‘Hortensia’, a tall perennial with double yellow daisy flowers is the plant that most have in mind when referring to the outhouse plant, though it has other common names. Yet, in online gardening groups, outhouse plant is used to refer to any tall plant that resembles a yellow daisy. Rudbeckia laciniata is the original species, the North American native cutleaf coneflower, that boasts large single yellow daisy flowers and a prominent grey-green center. It too is called the outhouse plant.

Hollyhocks (Alcea rosea), a tall biennial, is also called outhouse plant because it was commonly planted around outhouses. It would be a major shock to order “outhouse flower” expecting clumps of fluffy yellow Rudebckia laciniata ‘Hortensia’ only to receive the straight and stately Alcea rosea!

You might also find the name Rudbeckia laciniata ‘Golden Glow’. This is an incorrectly used name for Rudbeckia laciniata ‘Hortensia’.

The Proper Way to Name Your Propagated Plants

Plants can be produced using seeds or through vegetative processes and the method used determines the correct name of the new plant.

From Seed:

Species grown from seed will retain the name of the parent. A variety name can also be used if you are certain that only one variety could have pollinated the mother plant. For example, the name Cersis canadensis var alba can be used for seedlings if there are no red colored redbuds in the area that could have provided pollen. If red and white redbuds grow together, then seedlings should be called just Cersis canadensis.

Seedlings from cultivars should not be named with the cultivar name. A seedling from Rudbeckia laciniata ‘Hortensia’, should be called Rudbeckia laciniata.

Vegetative Production:

All vegetative techniques maintain the genetics of the parent plant and therefore such plants will take on the exact same name as the parent. Vegetative techniques include division, cuttings, layering and grafting.

Dealing With No-name Plants

If you have plants without a name and you identify them through pictures or social media, never assign a cultivar name to them. Use only the botanical name. Too many gardeners fail to do this and it causes a lot of confusion in the hobby.

For example, Phlox paniculata ‘David’ is a common white phlox. Many gardeners who have an un-named white summer phlox call it David, but there are numerous other such white phlox including seedlings of David, and none of these should be called David because they are genetically different.

Written by: Marika Li