THE OTHER ZONAL PELARGONIUMS – 11 –
FORMOSA, FOMOSUM AND FINGERED ZONAL PELARGONIUMS
By Wayne Handlos, Ph.D.
1. P. ‘Formosa’ - flower & leaf 2. P. ‘Red Witch’ flower & leaf 3. ‘St. Elmo’s Fire flower & leaf
4. Sweet’sP. formosum (1822) 5. Another P. formosum 6. ‘Elnaryd’s Twister’ (medusa-type)
What a disparate set of names for this group of zonalPelargoniums! The Formosum type of plants have a deeply
divided leaf (palmately lobed in botanist-language) which Holmes Miller likened to fingers and coined the name
"fingered flowered geraniums". The petals are narrow and the flowers relatively small. When first discovered, it was
questioned whether these plants were even in the genus Pelargonium. Over the years, crosses between the Formosa-
type Pelargonium, stellars and ordinary zonal Pelargoniums have established the close relationship of ‘Formosa’ to
the rest of the zonal Pelargoniums. Both Faye Brawner (Geraniums: The Complete Encyclopedia) and Annette
Andersson (www.geraniumsonline.com) have given accounts of the various cultivars which have been produced
over the years. Andersson’s article is available in Swedish at www.blakulla.eu/ and in Russian at www.pelargonium-
The distinctive Formosa/fingered leaf has been shown to be controlled by recessive genes. In recent
The distinctive Formosa/fingered leaf has been shown to be controlled by recessive genes. In recent years, an even
more extreme form of fingered leaf has been obtained where the leaf is reduced to a single "finger" or lobe. Catia De
Tomi who first obtained a plant like this, has proposed the name "medusa" for this category of plants with a tangled
mass of leaves.
All formosum cultivars stem from breeding work begun with the first fingered plant found at a hotel in Michoacan,
Mexico in the 1950’s. It was believed that sailors from Taiwan (Formosa) brought the first plant to Mexico but further
investigations have not found these plants anywhere else in the world. In hindsight these plants probably originated
from a chance mutation of some unknown zonal Pelargonium plant that an observant gardener grew in a hotel planter
box. The original plant is still available as ‘Formosa’ or ‘Formosum’ and is a relatively short, branching plant with
double, light salmon colored flowers with narrow petals. ‘Urchin’, ‘Red Witch’, ‘Playmate’ and ‘St. Elmo’s Fire’ are
variations on this theme with various shades of red and salmon flowers on shorter, well-branched plants.
As the original plant was thought to be from Formosa (Taiwan) that name was given to the cultivar. When this plant
was thought to be a distinct species the name was latinized to "formosum" to be in agreement with the generic name
Pelargonium. As early as 1959, Wm. Schmidt cautioned against the use of this name for the fingered Pelargonium.
In Latin "formosum" means "beautiful" not "from Formosa". Schmidt was also correct to say that Sweet had used
the name P. formosum for another, totally different plant. In truth the name has been used multiple times to refer to
different plants (by Balbis in 1826 for P. scabrum, by Desfontaine in 1809 for P. formosissimum, by Sweet in 1822 for
a P. cucullatum hybrid of uncertain origin, by Cels in 1824 for an unknown plant and by Poiret in 1812 for Geranium
formosum based on Desfontaine’s plant. Talk about confusing! By the rules, the fingered-leaved plants should be
called Pelargonium x hortorum cv. ‘Formosa’ or ‘Formosum’ depending on which name was correctly published first.
I haven’t tracked that one down yet. Under no circumstances should the fingered plants be called Pelargonium formosum.
The International Codes of Nomenclature notwithstanding, writers continue to use this name incorrectly. Some form of P.
formosum (probably Sweet’s plant) was popular in Europe in the early decades of the 1800’s and was commonly found in
flower shows there.
While some hybridizing work has been done with these plants, the modest form of the flowers probably has kept them from
becoming very popular. Holmes Miller’s breeding records (GATW, 1971, v. 19, # 1) indicate that ‘Formosa’ crossed with
dwarf zonals produces offspring that all have normal, rounded, zonal-type leaves. Self-pollinating these hybrids give some
offspring that have the fingered leaf-type indicating that the fingered leaf is a recessive character/gene. Faye Brawner and
others have indicated anecdotally that three-way crosses involving normal zonals, formosums and stellars can be made
indicating a close relationship among these plants. The cultivars are apparently diploids.
The Formosa/Formosum/Fingered floweredPelargoniums should be grown as any other zonal Pelargonium is grown:
well-drained soil, modest nutrients and bright light. Direct, hot sunlight may cause burning. Insect and disease problems
are minimal. The cultivars in this group are really novelties because of the unusual leaf form. The small stature of most of
them appeals to the collector of dwarfs and miniatures.