The plants commonly called “geraniums” at the nursery center are really pelargoniums, and are sometimes referred to as “zonal geraniums.” Could someone please shed some light on this confusion?
Douglas G. Larson, Bothell, WA
Dr. Allan Armitage, professor of horticulture at the University of Georgia in Athens, replies: The term geranium comes from the family (Geraniaceae) to which both Pelargonium and Geranium belong. They have similar flower structure, similar “cranesbill” fruit, and the foliage is remarkably similar in many species. But botanical differences also separate the two; most pelargoniums are in shades of red, pink, and white, while the predominate colors for geraniums are purple, blue, and white.
Another reason that pelargoniums may have been lumped under the same common name is that true geraniums (Geranium spp.)—native from Europe to Asia to North America—were likely in commerce in Europe before the annual pelargoniums were introduced from South Africa. Over time, the annual pelargonium became more popular than its look-alike cousin as a showy bedding plant, and became much more widely known as the “geranium.”
Pelargoniums are sometimes referred to as zonal geraniums because many of the cultivars have a dark purple zone on the leaves. Of course, many are not zoned (for example, the scented forms), but deep zonation has long been an objective of breeders of the annual bedding geranium (P. X hortorum). The zone is more apparent in cooler times, such as in spring and fall.
So, in a nutshell, the names are confusing and will continue to be.