elargonium is a genus of flowering plants which includes about 200 species of perennials, succulents, and shrubs, commonly known as geraniums (in the United States also storksbills). Confusingly, Geranium is the correct botanical name of a separate genus of related plants often called cranesbills or hardy geraniums. Both genera belong to the family Geraniaceae. Linnaeus originally included all the species in one genus, Geranium,
they were later separated into two genera by Charles L’Héritier in 1789.
Pelargonium species are evergreen perennials indigenous to Southern Africa, and are drought and heat tolerant, but can tolerate only minor frosts. They are extremely popular garden plants, grown as bedding plants in temperate regions.
The first species of Pelargonium known to be cultivated was P. triste, a native of South Africa. It was probably brought to the Botanical Garden in Leiden before 1600 on ships which stopped at the Cape of Good Hope. In 1631, the English gardener John Tradescant the elder bought seeds from Rene Morin in Paris and introduced the plant to England. The name Pelargonium was introduced by Johannes Burman in 1738, from the Greek
pelargós (stork), because the seed head looks like a stork's beak.
Pelargonium leaves are usually alternate, and palmately lobed or pinnate, often on long stalks, and sometimes with light or dark patterns. The erect stems bear five-petaled flowers in umbel-like clusters called pseudoumbels. The flower has a single symmetry plane (zygomorphic), which distinguishes it from the Geranium flower, which has radial symmetry (actinomorphic). The leaves of Pelargonium peltatum, Ivy-leaved Geranium,
have a thick
cuticle better adapting them for drought tolerance.
Pelargonium species are native to southern Africa and Australia, and the north of New Zealand. Others are native to southern Madagascar, eastern Africa, Yemen, Asia Minor and two very isolated islands in the south Atlantic Ocean (Saint Helena and Tristan da Cunha). Most of the Pelargonium plants cultivated in Europe and North America have their origins in South Africa.
Species, cultivars and hybrids
There is considerable confusion as to which Pelargonium are true species, and which are cultivars or hybrids. The nomenclature has changed considerably since the first plants were introduced to Europe in the 17th century.
Horticultural Pelargonium cultivars (as opposed to wild species) are classified into several major groups, with zonals subdivided further. Thousands of ornamental cultivars have been developed from about 20 of the species.
The major groups are;
* Zonals, which cover:
-Fancy leaf: Gold Leaf, Silver Leaf, Butterfly Leaf & Tri-Colour
-Fancy flowered: Carnation Flowered, Tulip Flowered, Cactus Flowered, Rosebud Flowered
* Ivy-leaved (the cultivars that trail and are used in hanging baskets or window boxes)
* Ivy x zonals: a hybrid cross of ivy leaf and zonals
* Frutetorum hybrids
Ivy-leaved (trailing) cultivars are mainly derived from P. peltatum. They have hanging stems and hardened leaves, and are used in hanging baskets.
Regal (Royal, French) varieties or P. × domesticum are mainly derived from P. cucullatum and P. grandiflorum. They have woody stems, wrinkled leaves and pointed lobes, and are mainly grown in greenhouses.
Zonal varieties, also known as P. × hortorum, are mainly derived from P. zonale and P. inquinans. They have round leaves with a coloured spot (or 'zone') in the centre (hence 'zonal'). One of the most common ornamental pot plants, with over 500 cultivars.
Cultivars are derived from a great number of species, amongst others P. graveolens. These include: Species
* Almond - Pelargonium quercifolium
* Apple - Pelargonium odoratissimum
* Coconut - Pelargonium grossalarioides (Pelargonium parriflorum)
* Lemon - Pelargonium crispum
* Nutmeg - Pelargonium fragrans (Pelargonium x fragrans)
* Old Spice - Pelargonium fragrans 'Logees'
* Peppermint - Pelargonium tomentosum
* Rose - Pelargonium graveolens (Pelargonium roseum)
* Rose - Pelargonium capitatum
* Rose - Pelargonium radens
* Lemon Scented - Pelargonium citronellum
* Southernwood - Pelargonium abrotanifolium
* Strawberry - Pelargonium scarboroviae (Pelargonium x scarboroviae)
* Pelargonium ionidiflorum
* Fiery-flowered stork's bill Pelargonium ignescens Scarlet Unique Scented Geranium
'Attar of Roses' - a cultivar of P. capitatum
'Crowfoot Rose' - a cultivar of P. radens
'Dr. Livingston' - a cultivar of P. radens
'Grey Lady Plymouth' - a cultivar of P. graveolens
'Prince Rupert' - a cultivar of P. crispum
'Ginger' - P. x torento
'Lemon Balm' - a hybrid: P. x melissinum
'Lime' - a hybrid: (P. x nervosum)
'Prince of Orange' - a hybrid: P. x citrosum
List of AGM cultivars
The following selection of pelargoniums have gained the Royal Horticultural Society's Award of Garden Merit:
* 'Attar of Roses' (rose scented leaves, pink flowers)
* 'Citriodorum' (lemon scented leaves, rose pink flowers)
* 'Dolly Varden' (variegated leaves, scarlet flowers)
* 'Frank Headley' (cream vareigated leaves, salmon pink flowers)
* 'Fringed Aztec' (regal group - white & purple fringed flowers)
* 'Gemstone' (scented leaves, pink flowers)
* 'Grace Thomas' (lemon scented leaves, pale pink flowers)
* 'Joy' (pink & white frilled flowers)
* 'Lady Plymouth' (P. graveolens variegata - small mauve flowers)
* 'Lara Candy Dancer' (scented leaves, pale mauve flowers)
* 'Lara Starshine' (aromatic leaves, lilac flowers)
* 'L'Élégante' (ivy-leaved, trailing, white and purple flowers)
* 'Mabel Grey' (lemon-scented leaves, mauve flowers)
* 'Mrs Quilter' (bronze leaves, salmon pink flowers)
* 'Radula' (lemon & rose scented leaves, pink & purple flowers)
* 'Royal Oak' (balsam scented leaves, mauve flowers)
* 'Spanish Angel' (lilac & magenta flowers)
* 'Sweet Mimosa' (balsam-scented leaves, pale pink flowers)
* 'Tip Top Duet' (pink & wine-red flowers)
* P. tomentosum (peppermint-scented leaves, small white flowers)
* 'Voodoo' (crimson & black flowers)
Other than being grown for their beauty, species such as P. graveolens are important in the perfume industry and are cultivated and distilled for their scents. Although scented pelargoniums exist which have smells of citrus, mint, pine, spices or various fruits, the varieties with rose scents are most commercially important. Pelargonium distillates and absolutes, commonly known as "scented geranium oil" are sometimes
supplement or adulterate expensive rose oils. The edible leaves and flowers are also used as a flavouring in desserts, cakes, jellies and teas. Studies have shown Pelargonium sidoides is effective for cough. Scented-leafed pelargoniums can be used to flavor jellies, cakes, butters, ice cream, iced tea and other dishes, The rose-, lemon- and peppermint-scents are most commonly used. Also used are those with hints of peach, cinnamon and orange. Commonly used lemon-scented culinary species include P. crispum and
P. citronellum. Rose-scenteds include P. graveolens and members of the P. ‘Graveolens’ cultivar group. Other species and cultivars with culinary use include the lime-scented P. ‘Lime,’ the lemon balm-scented P. ‘Lemon Balm,’ the strawberry-lemon-scented P. ‘Lady Scarborough’ and the peppermint-scented P. tomentosum.
Pelargonium species are used as food plants by the larvae of some Lepidoptera species, including angle shades.
The Japanese beetle, an important agricultural insect pest, becomes rapidly paralyzed after consuming flower petals of the garden hybrids known as "zonal geraniums" (P. x hortorum). The phenomenon was first described in 1920, and subsequently confirmed. Research conducted by Dr. Christopher Ranger with the USDA Agricultural Research Service and other collaborating scientists have demonstrated the excitatory amino
quisqualic acid present within the flower petals is responsible for causing paralysis of the Japanese beetle. Quisqualic acid is thought to mimic L-glutamic acid, which is a neurotransmitter in the insect neuromuscular junction and mammalian central nervous system.
* Pelargonium flower break virus
* Pelargonium line pattern virus
The primary uses have been for intestinal problems, wounds and respiratory ailments, but Pelargonium species have also been used to treat fevers, kidney complaints and other conditions. Geranium (Pelargonium) oil is considered a relaxant in aromatherapy, and in recent years, respiratory/cold remedies made from P. sidoides and P. reniforme have been sold in Europe and the United States. P. sidoides along with Echinacea is
used to treat
bronchitis. P. odoratissimum is used for its astringent, tonic and antiseptic effects. It is used internally for debility, gastro-enteritis, and hemorrhage and externally for skin complaints, injuries, and neuralgia and throat infections. The essential oil is used in aromatherapy. It is also used to balance the hormonal system, menstrual flow, and clean the body of toxins.