Sunday, February 24, 2019

Plant Story--Wild Geraniums, A Treat to See

geranium, genus Pelargonium
geranium, genus Pelargonium
Geraniums were introduced to American gardens by Thomas Jefferson at Monticello and were a hit. I certainly grew up knowing geraniums and thinking them dull.

That made wild geraniums relatively easy to identify. There are native species all over North America, fun to spot on a hike.
geraniums, also called cranesbills, genus Geranium
geraniums, genus Geranium

The common and scientific names are confused. The geraniums Jefferson planted were native to South Africa. Originally included in the genus Geranium (in the plant family named after them, Geranicaceae), the South African plants were given their own genus, Pelargonium in 1789 just three years after Jefferson introduced them to the U.S. But the common name geranium stuck.

Geraniums in the genus Geranium (about 430 species) are native all over the world, but especially Europe. Geraniums in the genus Pelargonium (280 species) are native all over the world but are particularly numerous in South Africa and the Southern Hemisphere.
geraniums genus Geranium
geraniums or cranesbills, genus Geranium
Some plant books call all the species in the genus Geranium cranesbills, which would be clear if people were consistent, but they're not. For example, the USDA calls most of the 14 native Geranium species geraniums (carolina geranium, Geranium carolinianum, spotted geranium Geranium maculatum), giving cranesbill as a common name only twice (Bicknell's cranesbill, Geranium bicknellii, western purple cranesbill, Geranium atropurpureum). The name cranesbill has the problem that plants in the genus Erodium (closely related, link) are called cranesbills (among other names).

In the United States if it "looks like a geranium" it is likely Geranium or Pelargonium. For geraniums, you can tell plants in the genus Geranium from Pelargonium because those of Geranium have five very similar petals and are radially symmetrical, while the two upper petals of Pelargonium look different from the three lower ones and so the flowers are symmetrical only along single line. (Symmetry is a very useful flower characteristic: radially symmetrical is called actinomorphic, bilaterally symmetrical zygomorphic. Lots of details of flower interaction with pollinators begin with the symmetry of the flower.) Cultivated doubles are likely Pelargonium. In addition, if it is a winter-hardy perennial, it is a Geranium because Pelargonium plants are killed by frost.

Of the four other genera in the geranium family, you might encounter an Erodium, called storksbill, cranesbill or filaree as two or three of the 80 species of Erodium are weeds in the U.S. and one, Erodium texanum, is native to the U.S. southwest. The remaining genera are not found in the United States except for a rare native, California macrophylla, called Erodium macrophylla by the USDA.

geranium or cranesbill, genus Geranium
geranium or cranesbill, genus Geranium
Radial symmetry means the plant is symmetrical
along each of those lines
geranium, genus Pelargonium
geranium, genus Pelargonium
Only a single plane of symmetry, the one drawn

Watch for wild geraniums, genus Geranium. North America has fourteen native Geranium species with wide enough distributions that you might spot one anywhere (USDA link).

The cranesbill name is descriptive. Plants in the geranium family have distinctive seed pods which were seen as looking like a crane's bill. Storksbill, another version of that description, is another common name for geranium family plants.
geranium with crane's bill shaped seed pods
The crane's bill-shaped seed pods. 
The cranesbill seed pod has a dramatic function. When Geranium seeds are ripe, the seed pod breaks at the base and fires the seeds away from the parent plant (ballistic dispersal, photo). In Erodium cicatrium (a widespread weed and easy to observe) a long filaments from the pod (awn) stays attached as the seed flies through the air. Then, on the ground, the awn twists as it dries, driving the seed into the ground. (link nice picture half way down). Some species of Geranium just fling their seeds without an awn (photo) while others send them with the awn to drill into the ground. When you encounter a wild geranium, check out its seed pods.

The flowers attract numerous interesting pollinators. Note the lines on the flowers. Those are nectar guides, acting like arrows "this way to the nectar."

geraniums, genus Geranium
wild geraniums, Geranium
likely Geranium viscosimum, sticky purple geranium
western Wyoming
wild geranium genus Geranium
wild geranium flower with native bee
photo from 1992, Rocky Mountains
wild geranium genus Geranium
wild geranium genus Geranium
probably Geranium richardsonii, 
Rocky Mountain National Park 2016
A patch of wild geraniums in Wyoming

I called the native North American geraniums I've seen all "wild geranium" but of course, depending on where you are your wild geranium with be properly called spotted geranium (link) or piney woods geranium (link) or maybe Carolina geranium (link).

Notice wild geraniums, maybe work out their exact name, but best of all, enjoy seeing them.
geranium, genus Geranium

Comments and corrections welcome.

Miscellaneous sources
Aedo, C. 2001. Taxonomic revision of Geranium sect. Brasiliensis (Geraniaceae). Systematic Botany 28 (2): 205-215.
Crook, J. 2013. A short history of the geranium. link Accessed 2/22/19
Evangelista, D., S. Hotton and J. Dumais. 2011. The mechanics of explosive dispersal and self-burial in the seeds of the filaree, Erodium cicutarium (Geraniaceae). Journal of Experimental Biology. 214: 521-529.
Aldasoro, J., C. Navarro, P. Vargas, L. Sáez and C. Aedo. 2002. California, a new genus of Geraniaceae endemic to the southwest of North America. Anales Jard. Bot. Madrid. 59 (2): 209-216.
Stevens, P. F. (2001 onwards). Angiosperm Phylogeny Website. Version 14, July 2017 [and more or less continuously updated since]." Accessed 2/22/19.

Kathy Keeler, A Wandering Botanist

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