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Zonal Geranium

Plant of the Week

Zonal Geranium
Latin: Pelargonium x hortorum

Picture of two potted Zonal Geraniums with bright red flowers.

Geraniums are a common part of the garden scene in Arkansas with a long history of cultivation and thousands of selections to choose from.

Zonal geraniums have been grown in Europe since 1632 when John Tradescant, the gardener for Charles I of England, took the plants back to Europe from their native South Africa.

A gardener working for Napoleon’s Empress Josephine, is credited with producing the first hybrids in the late 1700s. But it wasn’t until the early 19th Century, during the great horticultural craze for new plants, that the modern day geranium in all of its varied forms came into being through hybridization. During that era -- if the modern day university system had existed – there would have been a Department of Geraniology to study this exciting new group of plants.

The geranium is, in nature, a hardy shrub with fat, succulent stems that evolved in the dry, frost-free highlands of South Africa, where temperatures are moderate during the growing season. The old practice of knocking soil from the roots and hanging the plants under the house for the winter is an acknowledgment of the geranium’s ability to survive periods of drought and neglect. The zonal geranium of today, so called because of the band or maroon that forms a circle on the leaf, is available in a wide array of colors ranging from white to pink, red and orange. Red is the most common color.

For as tough as geraniums are in the garden, they are rather difficult to produce on large scale as is done for the greenhouse industry. Before WWII, most greenhouse growers maintained a few geranium stock plants to use for producing cuttings the following spring. In the years after the war, it was realized that geraniums could be grown in Southern California with cuttings shipped nationwide, thus eliminating the need for growers to maintain their own plants.

This method worked well for a few years, until a wet year in the early 1950s in the geranium growing area resulted in an outbreak of a bacterial disease. Plants infected with geranium blight were sent throughout the country, and within a few years almost all geranium plants were showing symptoms of this serious disease that quickly killed infected plants.

Growers, working with plant pathologists, quickly developed a way of indexing their plants to see if they were free of the bacterium. Once a group of plants was shown to be disease free, they were used as the stock plants for propagation. The same procedure is still used today but most geraniums today are grown in Mexico with unrooted cuttings shipped to stateside growers.

Geraniums love bright sunlight, but they don’t like it too hot. When the temperature is above 95 degrees Fahrenheit, they stop flowering. If the temperature persists too long, they may even turn yellow.

In Arkansas, they are usually at the best in the spring and early summer and fall – July and August are just too hot for them to flower consistently. Because geraniums have been highly hybridized, they require frequent fertilization to keep them in active growth and producing lots of flowers. Once the flower head begins to fade, they must be removed to keep the plant tidy and to keep future blooms coming.

By: Gerald Klingaman, retired
Extension Horticulturist - Ornamentals
Extension News - February 26, 1999

 

The University of Arkansas Division of Agriculture does not maintain lists of retail outlets where these plants can be purchased. Please check your local nursery or other retail outlets to ask about the availability of these plants for your growing area.