* Widely-grown and commonly misnamed "geraniums" should be called "Pelargoniums."
More on The Geranium Family (Geraniaceae) & the Genus Pelargonium
By Wayne Handlos, Ph.D.
The geranium family consists of several genera of plants commonly referred to as geraniums or cranesbills. The genus for which the family is named is Geranium. These are plants primarily of temperate areas and are now frequently referred to as “hardy geraniums.”
The genus which most of our members grow is called Pelargonium. These plants are primarily from Southern Africa – many are from the Mediterranean climate area of South Africa. This makes them at home in southern California where we also enjoy a Mediterranean climate. Erodium is another genus in the geranium family. A couple of species are grown in gardens and are available commercially. Two or three species of Erodium are common weeds in the fields of California.
Monsonia is yet another genus in the geranium family. This genus is rare in cultivation and in southern Africa species are commonly viewed as weeds. Sarcocaulon (sometimes included in the genus Monsonia) are succulent species in the geranium family. They are found in the deserts of southern Africa. These plants have become popular among the cactus and succulent growers.
Types of Pelargoniums: Zonal geraniums* ( Pelargonium x hortorum), Ivy geraniums* (Pelargonium peltatum),
Regal or Martha Washington geraniums* (Pelargonium x domesticum),
Angel geraniums*, Scented leaf geraniums* Unique geraniums*, Dwarfs and Miniatures.
ZONAL GERANIUMS* – (known scientifically as Pelargonium x hortorum) are the classical garden geraniums. These are plants with large clusters of brightly colored flowers borne on long stalks, usually held well above the foliage of the plants. The leaves are rounded and sometimes have a darker band of brown on the leaves. ‘Savannah Coral’, ‘Designer Dark Red’ There are several subcategories of zonal geraniums. These include the carnation flowered types, rosebud geraniums, cactus flowered geraniums, bird’s egg geraniums, phlox eyed, striped and speckled flowers, stellar geraniums, fancy leaf or variegated leaf geraniums, dwarfs and miniatures.
Carnation flowered geraniums* – The petals of these flowers have a toothed or fringed edge.
Rosebud geraniums* – This type of geranium has flowers which are very double, that is, they have many petals so the flowers look like small, double roses.
Cactus flowered geraniums* – In these flowers the petals are rolled and twisted. The flowers are like miniature cactus flowered dahlias.
Bird’s egg geraniums* – The petals of these geraniums have tiny spots or dots of color at their center. Several of the new cultivars of seedling geraniums show this characteristic. ‘Horizon’ cultivars, ‘Designer Dark Pink Sizzle’
Phlox eyed geraniums *– The flowers of these plants have a lighter colored center. This is a popular variation seen in many new cultivars of Pelargonium. ‘Horizon’ cultivars, ‘Designer Picotee Salmon’
Stellar geraniums*– In these plants both the leaves and petals are fringed, forked or deeply toothed or lobed. ‘Supernova’, ‘Louis West’, ‘Vancouver Centennial’
Striped or speckled flowers* – In these plants petals are variously striped and/or speckled with a different color or shade of color. In the past these have been referred to as paint box geraniums or New Life geraniums. Every petal has a different pattern and sometimes a whole petal or even the whole flower will be a single color. ‘Designer Peppermint Twist’
Fancy leaf geraniums* – This group is distinguished by the various colorations shown on the leaves. In the simplest types, the margin of the leaf is whitish, cream or yellowish in color. This is a simple form of variegation. In other cultivars a darker band of color is superimposed on the green and white variegation adding a reddish or brownish color to the leaves. These varieties are referred to as tricolors. Sometimes the center of the leaf is lighter or darker colored. These are called butterfly leaf geraniums. (Variegated leaf cultivars are also found in other types of geraniums too.) In some cultivars, the whole leaf is a lighter shade of green and these are commonly referred to as golden leaf geraniums. Many of the fancy leaf geraniums are sensitive to strong, direct sunlight and grow best in somewhat shady locations. The general recommendation is for morning sun and afternoon shade. ‘Persian Queen’, ‘Frank Headley’, ‘C.J. Mappin’, ‘A Happy Thought’, ‘Santa Maria’, ‘Indian Dunes’, ‘Pink Happy Thought’, ‘Crystal Palace Gem’
DWARFS and MINIATURES - These are zonal geraniums but they remain small when full grown. These are particularly popular as small house plants though they are rarely seen in stores. Small plants available commercially are frequently treated with growth regulators which chemically dwarf the plant. True miniatures are defined as mature plants less than five inches in height while dwarfs are those plants between five and eight inches tall. Plants over eight inches tall are considered regular sized zonals. ‘Winnie Read’, ‘Aztec’, ‘Memento’
IVY GERANIUMS* – Scientifically these are known as Pelargonium peltatum. This is a distinct species of Pelargonium which has a trailing habit of growth. They are useful in hanging baskets or as ground cover plants. These plants show a variety of leaf types including variegated types. Some have a peltate leaf (from the scientific name peltatum) where the petiole (leaf stalk) is attached within the leaf blade, while other types have the petiole attached to the margin (edge) of the leaf. Some have leaves which are more rounded while others have large triangular teeth or lobes. Some cultivars have striped flowers. This is due to the presence of a benign virus which can be transferred to any cultivar to create the bicolored flower. ‘Pacific Lavender’
REGAL OR MARTHA WASHINGTON GERANIUMS *– Scientifically this group is named Pelargonium x domesticum. This group of cultivars is characterized by large flowers which are frequently heavily veined and patterned. The leaves are fairly large, coarsely toothed and occasionally fragrantly scented. These plants require cool night temperatures to initiate flowering so they do particularly well in coastal California. In other areas of the U.S. the night temperatures are too warm and blooming is curtailed. The flower petals may be ruffled, fringed and variously speckled. In some cultivars the flowers have multiple colors making them particularly intriguing. ‘South American Bronze’, ‘Conchita’, ‘Rembrandt’, ‘Donatella Florence’, ‘Rhodomine’, ‘Blue Moon’, ‘Pompei’
ANGEL GERANIUMS* – This is a group of cultivars of diverse ancestry. Generally the plants are small with small flowers. The flowers may resemble small regal flowers. The plants frequently are lax in growth and do well in hanging baskets. The two upper petals are often more darkly colored than the three lower petals. The colors tend to be in the lavender and pink part of the spectrum. A few cultivars have fringed or ruffled petals. Occasionally the leaves may be lemon scented and a few cultivars have variegated leaves with a whitish or yellowish margin. Flowers tend to be produced seasonally so are probably produced in response to cool night temperatures like the regal geraniums. ‘Little Rascal’, ‘April Showers’, ‘Daniella Marie’, ‘Ruffles’
SCENTED GERANIUMS* – This is a group of species of Pelargonium and their various offspring and hybrids. Generally the leaves have a pleasant scent – lemon, rose and mint are the common types. But in addition there are some lesser known types with other scents – strawberry, peach, pineapple, apple, nutmeg, clove/cinnamon, coconut, ginger, cologne/after shave. In addition there are a number of types that are less than pleasantly scented and are generally called “pungent”. Some of these are just odd scents, while others are definitely unpleasant. These plants vary from small and dainty to large and coarse in growth habit. Most flower seasonally. Some have large attractive flowers while others are small and somewhat inconspicuous. They are generally tough and resilient. ‘Cody’s Nutmeg’, P. radens, ‘Torento/Ginger’, ‘Apple Cider’, P. citronellum
UNIQUE GERANIUMS* – This is another group of distinctive plants with medium sized flowers on vigorous plants with lobed or divided leaves which are scented. The flowers tend to be in the red, rose, pink spectrum. They are borne in terminal clusters of a few to many flowers. The flowers are commonly veined with a darker color. The bloom period is long on the Central Coast of California. Seeds are rarely produced so the plants must be propagated from cuttings. These plants are quite hardy and even if frozen to the ground, tend to sprout again from the roots. ‘Shrubland Rose’, ‘Ashby’, ‘White Unique’
SPECIES GERANIUMS*– Species geraniums are those plants that are found growing wild in their natural habitat. They may still be found there today or they may be types that have been brought into cultivation but are essentially unchanged from their wild ancestors. Most of these are plants that do not have scented leaves though there are several that have scented flowers (an unusual occurrence in the genus Pelargonium). P. acetosum, P. acraeum, P. echinatum, P.exstipulatum, P. grandiflorum, P. tetragonum
SPECIES HYBRIDS – In recent years a category called species hybrids has been used to describe some of the plants being introduced into cultivation. The name implies that new types of plants are produced by crossing two different species of Pelargonium. In truth, this category could be used to describe many of the plants in the categories listed above including the common zonal, ivy, regal, angel, unique and scented geraniums. For some of the plants that have been recently hybridized we may know the ancestral species. This is easy but in other cases we can only guess at the ancestors involved in a particular cultivar (whose origins are lost in the mists of time or that originated as spontaneous volunteers in a garden). Such plants are no less interesting and make some nice contributions to the spectrum of plants we can (and should) grow. ‘Rager’s Five Spot’, ‘Ruby Ears’, ‘Caliente Fire’, ‘Galleria Bright Sunrise’