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Pelargonium // 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, but 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 πελαργός, pelargós (stork), because the seed head looks like a stork's beak. The chemist, John Dalton, first realized that he was color blind when he heard others describe the color of the flowers of the pink (Pelargonium zonale), as pink or red, when to him it looked either pink or blue, having no relationship to red at all.
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. 
Despite not being frost-hardy, pelargoniums are extremely easy to grow and to propagate. As they are evergreen perennials, they can be kept in flower throughout the winter months in a sufficiently favoured spot (or indoors). There are even one or two fully hardy species from Turkey. Their main requirement is a warm, sunny, sheltered location. Many varieties will tolerate drought conditions for short periods. They are commonly seen in bedding schemes in parks and gardens, but can also be grown indoors as houseplants if given enough light. More compact erect and trailing varieties are ideal for window boxes and hanging baskets, in association with other half-hardy plants like lobelias, petunias and begonias. Thousands of pelargonium cultivars are available from garden centres or specialist suppliers during the spring and summer months. They are regular participants in flower shows and competitive events, with numerous societies devoted exclusively to their cultivation. They are easy to propagate from cuttings.
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;
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
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 used to supplement or adulterate expensive rose oils. The edible leaves and flowers are also used as a flavouring in desserts, cakes, jellies and teas. 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.
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 acid called 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.
A study by the Laboratory of Apiculture & Social Insects group at the University of Sussex on the attractiveness of common garden plants to pollinators found that a cultivar of Pelargonium x hortorum was unattractive to pollinators in comparison to other selected garden plants such as Lavandula (lavender) and Origanum.
|This section needs more medical references for verification or relies too heavily on primary sources. (March 2013)|
In herbal medicine, Pelargonium has been used for intestinal problems, wounds and respiratory ailments, but Pelargonium species have also been used for 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 for bronchitis. P. odoratissimum is used for its astringent, tonic and antiseptic effects. It is used internally for debility, gastroenteritis, and hemorrhage and externally for skin complaints, injuries, and neuralgia and throat infections.[medical citation needed] The essential oil is used in aromatherapy. It is also used to balance the hormonal system, menstrual flow, and clean the body of toxins.[unreliable medical source?]
Pelargonium graveolens scented leaf
Pelargonium quercifolium 'Fair Ellen' (scented leaf)
P. × hortorum zonal
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