Geraniums are among the most popular flowers grown. There are many different species of geraniums, including Martha Washington, ivy, scented-leaved, mosquito and, of course, the standard bedding geranium. Bedding geraniums are available as Zonal and seed geraniums and can be used as annual bedding plants, in hanging baskets, in window boxes and as houseplants. There are distinct differences between Zonal and seed geraniums and the two varieties can be distinguished by a few key visual attributes.
Note the zone of darker pigment on this Zonal geranium.
Pelargonium x hortorum is the Latin name for common geraniums. Both Zonal and seed geraniums bear this name, and are therefore very similar. The main difference is in how they are propagated. There are a few visual differences between Zonal and seed geraniums. Zonal geraniums get their name from a band or "zone" of anthocyanin (red plant pigment) in the middle of the leaf that is darker than the surrounding green foliage. Zonal geraniums are often double flowered and have larger flower heads.
Zonal Geranium Propagation
Zonal geraniums are often grown in 4-inch pots.
Zonal geraniums are propagated by cuttings, or taking a leaf clipping and rooting it in a potting medium. Years ago, wholesale growers would have stock plants that would be grown outdoors in summer then brought in the greenhouse in the fall before a killing frost. Cuttings would be taken and rooted during the winter, then forced in the spring. Today, due to the high cost of greenhouse maintenance, specialty growers focus on rooting cuttings and shipping out to wholesale growers in early spring for finishing.
The flowers of seed geraniums are often single, but there are more per umbel.
For years, geraniums were primarily grown by cuttings. In the 1970s, researchers at Pennsylvania State University developed the first true F1 hybrid seed geraniums. Seed geraniums are generally smaller plants, with smaller but more numerous flowers. Seed geraniums tend to branch out more successfully, making them a great choice for seed pack production. Seed geraniums come in many colors including: red, pink, white, orange, salmon, bi-color and many colors in-between. Seed geraniums are often less expensive than Zonal geraniums.
Propagating Seed Geraniums
As the name indicates, seed geraniums are propagated by seed. Geranium seed comes raw, refined or primed. Primed seed is the raw seed coated to increase germination. The seed coat on geranium seed is very hard, and is often scarified, or scratched to break the seed coat. Germination takes seven to 14 days at 75 to 78 degrees Fahrenheit. This process begins three months prior to the last frost. Seedlings are transplanted into 4-inch pots and pinched back to produce tighter branching.