Jennifer Schultz Nelson
Extension Educator, Horticulture
At first mention of the word geranium, I imagine most of us picture a red-flowered annual. Technically speaking though, what we commonly refer to as a geranium is a member of the genus Pelargonium. There is a genus Geranium, which is related to Pelargonium, but they look very different.
The genus Geranium contains over 400 species of annual, perennial, and biennial plants, originating in many temperate regions of the world. Most of the types commonly cultivated are natives of the Mediterranean.
Commonly Geranium is found sold as 'Hardy Geranium' to distinguish it from the Pelargoniums. Another common name is 'cranesbill', in reference to the seed heads, which are said to resemble the bill of a crane. The name Geranium itself comes from the Greek word "geranos", which means crane.
The true Geraniums typically have showy foliage, but also have attractive 5-petaled flowers in shades of pink, blue, lavender and white. Some cultivars are double-flowered, where each flower has at least two layers of petals. A double-flowered cultivar I've planted and really enjoy is 'Birch's Double' which has violet-blue double flowers.
The genus Pelargonium includes about 200 different species of flowering annuals and perennials, some of which grow to the size of small shrubs in their preferred environments. Linnaeus, the scientist who established the system we use today of naming plants with Latin names had originally included Pelargoniums in the same genus as Geraniums. Perhaps this is the origin of the confusion in the name 'geranium'. In the late 1700's the Pelargoniums were placed in their own genus.
The first cultivated Pelargonium was Pelargonium triste, from South Africa. It is thought the plant was brought to Europe sometime before 1600 by ships that had stopped at the Cape of Good Hope in South Africa. The name Pelargonium has an origin very similar to that of true Geraniums. The name Pelargonium comes from the Greek word "pelargos" meaning stork, in reference to the plant's seeds looking like a stork's bill.
Most Pelargoniums are grown for their beautiful flowers and foliage. Using about twenty different species, breeders have generated thousands of cultivars. The leaves may have light and dark patterns on them, and the flowers come in an astounding range of shapes and colors, from star and funnel shapes, single- or double-flowered, white, pinks, reds, oranges, and purples.
Pelargonium cultivars are typically divided into four broad categories: zonal, ivy-leaved, Regal, French or Martha Washington, and scented leaf.
Zonal pelargoniums are what we think of as a 'typical' geranium. The ones you find for 99 cents at the local nursery fall into this category, but you'll find some pricier fancy cultivars in this group as well. They are typically very heat and drought tolerant.
Ivy-leaved pelargoniums are just that–their leaves are shaped much like an ivy leaf. They have a trailing growth habit and look great in hanging baskets and window boxes. This group handles heat and drought less well than the zonal group–they need afternoon shade when temperatures climb above 85 degrees, and perform best with moderate soil moisture that does not fluctuate.
Regal pelargoniums are also called French or Martha Washington geraniums. These are very large-flowered, and tend to have spectacular color combinations on the flowers. The ones that usually catch my eye are a dark pink or purple edged in white or pastel shades. These are best kept indoors, as the heat of summer inhibits flowering for this group.
Scented leaf pelargoniums are grown more for their foliage and scent than their flowers, which tend to be small and nondescript. They are available in a wide range of scents, including lemon, peppermint, nutmeg, chocolate, and rose.
The leaves may be used to scent potpourris and flavor foods, but the only one with real economic value for its scent is Pelargonium graveolens, which has a rose scent. True rose oil is incredibly expensive and difficult to extract, while the oils of P. graveolens are far more economical and easy to produce, and only the most highly trained noses can tell the difference. Perfume makers extract the oils from this plant and use it in addition to or in place of oils extracted from roses.
The 'Holy Grail' of Pelargonium breeding had been a true yellow-flowered cultivar. In 2006, a German company announced the release of the cultivar 'Guernsey Flair', a true yellow Pelargonium reported to be an easy-to-grow and vigorous plant with lots of lemon-yellow blooms. There was only one catch: the only place to buy the plants was through the British version of the home shopping channel QVC. In their debut on QVC in March 2006 the 17,500 plants available sold out in a matter of minutes. In 2007 they were available on a limited basis from at least one other British company. Keep your eye out–they're bound to make it to U.S. catalogs someday.
No matter which genus you choose to grow–Pelargonium or Geranium, good drainage is key to success. In soil that does not drain well, plants in both genera will very likely develop root rots or other diseases related to too much water. Reduce the chances of developing these problems by improving soil drainage and allowing plants to dry slightly between waterings, but not to the point of wilting.
Pelargoniums may not be winter hardy, but they are a great plant to overwinter indoors and practice your plant propagation skills with. The key to success at overwintering indoors is to give the plant as much light as you can, and watch out for overwatering. Too much water will kill a Pelargonium very quickly indoors. Some people take cuttings rather than save the entire plant. Pelargoniums will root readily from cuttings placed in vermiculite.
Another option is to dig up your plants, remove most of the soil, and hang them upside down in a cool basement or garage that does not freeze. If the plants appear to be drying out too much, soak the roots in water overnight occasionally over the winter. In the spring, replant them, water well and cut them back by about two thirds. Fertilize with a balanced fertilizer when new growth appears.