Janet has been passionately growing pelargoniums since a child. She is member of the Geranium and Pelargonium Society.
The difference between geraniums and pelargoniums is often subjected to debate, but fortunately it's easy to clear things up by simply taking a closer look into both types of plants.
Despite the fact that the terms geraniums and pelargoniums are often used interchangeably, 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 the two becomes quite clear once we take a look at some pictures and learn more about these two charming, related plants.
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.
When the geranium seed head matures, the "beak" pops open ejecting the seeds out some distance so to grant better dispersal.
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.
Geranium leaves tend to be long, broadly roundish in form, and are described in botany as being "palmately cleft" meaning they have lobes radiating from one point with indentations extending about halfway to the base.
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.
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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.
When the seed heads mature, the seeds are dispersed by the wind. The seeds have a typical corkscrew shape which enhances their ability to penetrate into the ground.
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. Some leaves also are known for their velvety, soft texture.
The leaves of the ivy-leaved variety resemble ivy and have a waxy layer for better drought tolerance.
The leaves of the scented-leaved, as the name implies, boast a variety of appealing scents.
How All 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? In order to understand what happened, we need take a step back into history. This will allows us to finally 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. This misclassification took some time to correct.
It was only in 1789 that Charles L’Hertier, an 18th-century French botanist, decided to separate them into two different genera.
For some reason, despite the split, many still commonly refer to pelargoniums as geraniums. While this is incorrect, many garden centers and nurseries still use the term geranium when marketing their plants simply because the use pelargonium may have many potential buyers confused.
Differences 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, but can be also found in Africa and South America.
Pelargoniums are subshrubs from the Southern hemisphere that grow 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.
As mentioned, both plants adopt different seed dispersal techniques: 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, you may notice usage of the term geranium occasionally here and there.
In the articles presented here, both geranium and pelargonium terms may be used, but it's mostly for ease of search. Many people will use the term geranium in search engines, when in reality they're seeking information about pelargoniums.
The name Pelargonium Place will help clear things up, along with this article and the pictures displayed.
Flowers have five equal petals
Flowers have top 2 petals different from the lower 3
Flowers are blue, purple, pink and white, but never red or yellow.
Flowers can be red, pink, yellow, white, purple, but never blue.
Seeds are ejected
Seeds are spread by wind
Not cold hardy
This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.
© 2022 Janet