Geranium or Pelargonium: Old Names Die Hard!

Name the mystery plant! Photo: www.crocus.co.uk

Quick! What is the name of the plant in the photo above? I’ll bet 9 gardeners out of 10 said “geranium,” but they’re sorta, kinda wrong. It’s actually a pelargonium: a zonal pelargonium (Pelargonium × hortorum), to be exact. But we’ve been calling it by the wrong name for a long time now.

The confusion dates back over 250 years. In 1753, Linnaeus, busily classifying the plants of the world according to his new system of binomial botanical names, figured that the new-fangled semi-succulents with attractive flowers and odoriferous leaves just arriving from South Africa were very close relatives of the better-known geraniums (Geranium spp.) and lumped them into the same genus, under the name Geranium. Other taxonomists had already named the South African plants Pelargonium, but either Linnaeus was unaware of that or chose to ignore it. 

It took 35 years before someone corrected the error. Charles L’Héritier officially separated them into two different genera in 1789, putting the (mostly) Northern Hemisphere plants into the genus Geranium and the (mostly) Southern Hemisphere ones back into the genus Pelargonium. And that separation has held true over the centuries. 

That means your garden variety “zonal geranium” is actually a pelargonium—(Pelargonium × hortorum)—, which you should call a zonal pelargonium. This is also true of all the other South African imports, plants you may have been calling ivy geraniums, scented geraniums or regal geraniums, but which should by rights be called ivy pelargoniums (P. peltatum), scented pelargoniums (P. graveolens and others) and regal pelargoniums (P. ×  domesticum). 

That wasn’t so much of an issue back when gardeners grew mostly pelargoniums (the frost-tender South African types). If you used the word “geranium,” everyone understood you. But for the last 50 years or so, true geraniums (Geranium spp.) have become widely popular in temperate climate gardens. I mean, who doesn’t grow either Geranium Rozanne® or G. ‘Johnson’s Blue’? To distinguish them from the tender (half-hardy) pelargoniums, few of which can survive the winter in temperate climates, we took to calling the latter “hardy geraniums.”

To Beak or Not to Beak?

Of course, the two plant genera, Pelargonium and Geranium are closely related. Both belong to the same plant family, the Geraniaceae, and both have the same long, narrow, beak-shaped seed capsule that springs open when ripe and casts the seeds far and wide. In fact, the botanical names both refer to this same phenomenon.

Pelargonium is derived from the Greek word for stork, because the seed capsule is said to resemble a stork’s bill, while Geranium means crane, because it’s supposed to look like a crane’s bill. Honestly, you’d have to be a fairly serious ornithologist to be able to tell a stork’s beak from a crane’s beak … especially if you removed the rest of the bird! The seed capsules, therefore, are essentially identical.

Other than that, though, they’re very different. Certainly, you can’t grow them the same way and you can’t cross them together. 

Time to Change

It’s time to stop pussyfooting around. Why not call a Geranium a geranium and a Pelargonium a pelargonium?

This should be easy. It’s not as if I’m springing something new on you: after all, the names were changed over 250 years ago!

Plus, most gardeners already know the difference and are familiar with the term “pelargonium,” even if they don’t always use it. For example, if I use the term “zonal pelargonium” in a lecture, there are no confused faces: everyone gets it right away. 

And this correction had become all the more necessary in that an increasing number of varieties in both genera are now being grown.

When someone tells me about a new “geranium” they are growing, I’m always confused at first and I’m sure you are too. Are they referring to a geranium (hardy) or a pelargonium (tender)? A plant to grow permanently in the outdoor garden (geranium) or to bring indoors in winter (pelargonium)? And confusion is never a good thing.

For those who don’t quite get the difference, here’s a quick summary:

Pelargoniums (Pelargonium spp.)

• Tender plants (not cold resistant), mostly from South Africa;
• Grown as annuals or brought indoors for the winter;
• Most have sturdy stems, often upright, that survive from one year to the next;
• Originally, all pelargoniums had asymmetric flowers, with two upper petals quite distinct from the three lower petals, but that characteristic has been bred out of many modern pelargoniums. The average zonal pelargonium (Pelargonium × hortorum) of today, for example, now has symmetrical flowers, with all five petals being identical.

Geraniums (Geranium spp.):

• Cold hardy (there are a very few exceptions) and mostly native to the Northern Hemisphere;
• Grown outdoors year-round, almost never indoors;
• Herbaceous perennials (they usually die to the ground or to creeping rhizomes in the winter, then sprout again in the spring).
• Always have symmetric flowers: 5 petals of approximately equal size and shape.

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So, there you go. You may say po-TAE-to and I may say po-TAH-to, but let’s all say geranium when we mean Geranium and pelargonium when we mean Pelargonium.

Article adapted from one published on August 23, 2015.