Geranium Guide

Difference Between Geraniums and Pelargoniums

 

The difference between geraniums and pelargoniums is often a subject of debate, but no worries, we are here to finally help clarify things. The terms geraniums and pelargoniums are often used interchangeably, but in reality they are quite different plants.  Turns out, the majority of plants that we commonly refer to as “geraniums” are in reality pelargoniums. Fortunately, the difference between geraniums and pelargoniums becomes quite clear once we take a look at some pictures and learn more about these two charming related plants.

difference between geraniums and pelargoniums
Geraniums have 10 fertile stamens.

What are Geraniums?

Geraniums are plants that belong to a genus of  flowering plants that include as many as 430 species.

The name geranium derives from the Greek word (géranos) meaning ‘crane’. Its English name, ‘cranesbill,’ derives from the fact that the fruit capsule of some species is long and resembles the bill of a crane.

Geraniums are also often referred to as “hardy geraniums” for their ability to withstand cold weather. This distinguishes them from pelargoniums. However, not all geraniums are considered truly cold hardy.

The flowers typically have five petals that come in the colors of white, pink, purple or blue. Every petal is often characterized by its distinctive veining. The leaves of geraniums are long, palmately cleft and broadly circular in form.

What are Pelargoniums?

Most plants that many people commonly call geraniums, including several varieties such as the zonals, ivy-leaved and scented-leaved are in reality pelargoniums. Pelargoniums are a genus of flowering plants that include as many as 280 species.

The name Pelargonium derives from the Greek term pelargós meaning stork because, when the flowers form a seed head, it resembles the long and slender beak of a stork. Hence, why pelargoniums were also referred to as storksbill by the early enthusiasts.

Pelargonium flower heads feature clusters with flowers that open from the center outwards. Their inflorescence somewhat resembles the ribs of umbrellas; hence why this type of flowering arrangement is referred to as “umbel,” from the Latin word  “umbella ” meaning “parasol, sunshade.”

The leaves of zonal pelargoniums are typically thick and fleshly and may range in shape from round to lobed. Sometimes the leaves present a typically darker horse-shoe pattern. The leaves of the ivy-leaved variety resemble ivy and have a waxy layer for better drought tolerance.

How the Confusion Began

Both geraniums and pelargonims belong to the family Geraniaceae which comprises 830 species including  five genera under the form of herbs or subshrubs. The most important genera include Geranium (430 species), Pelargonium (280 species) and Erodium (80 species).

However,  although geraniums and pelargoniums belong to the same family, they belong to a different genus. So if both plants belong to a different genus, why are they so often confused? If we take a step back in history to better understand this we can see how all the confusion started.

Carl Linnaeus, a Swedish botanist, physician, and zoologist known for naming species of living things, used to provide names to animals and plants composed of two parts. The first part identified the genus to which the species belongs; whereas, the second part provided the specific name that identified the species within the genus.  This two-term naming system is called “binomial nomenclature” also referred to as taxonomy. 

So for example, us humans are identified by the name of homo sapiens which was provided by Linnaeus in 1758. Homo specifies that we belong to the genus Homo, while sapiens specifies the species.

Back in time, Linnaeus categorized both geraniums and pelargoniums under one genus. It was only in 1789 that Charles L’Hertier, an 18th-century French botanist, decided to separate them into two different genera. 

The Difference Between Geraniums and Pelargoniums

Despite belonging to the same family (geraniaceae), geraniums and pelargoniums have several differences that set them apart.

Geraniums are herbaceous perennials of the Northern hemisphere that can be also found in Africa and South America. Pelargoniums, on the other hand, are subshrubs from the southern hemisphere and occur naturally almost entirely within South Africa.

While both geraniums and pelargoniums have for the most part 5 petals, morphologically, when looking at the flower symmetry of these plants, we can note some differences. Floral symmetry describes how a flower can be divided into two or more identical, mirror-image parts.

Geraniums have actimorphic flowers (star-shaped). These flowers have five very similar petals and can be divided into 3 or more identical sectors passing through their center with typically each sector containing one petal and one sepal and so on. Another term for this characteristic is radially symmetrical.

Pelargoniums have slightly zygomorphic flowers. These flowers are more asymmetrical, having two upper petals that are different from the three lower petals. The flowers can be divided by a single plane which passes through their center into two mirror-image halves, just as a person’s face. Another term for this characteristic is monosymmetry or bilateral symmetry.

Even seed dispersal is different between the two: geraniums tend to disperse their seeds when their beak-like column ripens and springs open, shooting the seeds out some distance; whereas pelargonium seeds are carried away with the wind.

As seen, there is quite a difference between geraniums and pelargoniums! However, since most gardeners and nurseries seem to have accepted this misnomer, we too have decided to use the term geranium, hence the reason for the name of this website: Geranium Guide.