Pelargonium

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Pelargonium
P. peltatum
Scientific classification
Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Rosids
Order: Geraniales
Family: Geraniaceae
Genus: Pelargonium
L'Hér.
Species

About 200:
Pelargonium asperum
Pelargonium australe
Pelargonium capitatum (L.) L'Hér. ex Aiton
Pelargonium cotyledonis
Pelargonium cucullatum
Pelargonium drummondii
Pelargonium graveolens
Pelargonium grossularioides
Pelargonium insularis
Pelargonium littorale
Pelargonium peltatum
Pelargonium quercifolium(L. f.) L'Hér. ex Aiton
Pelargonium radens
Pelargonium rodneyanum
Pelargonium scabrum
Pelargonium sidoides
Pelargonium triste
Pelargonium vitifolium
Pelargonium × domesticum L.H. Bailey (pro sp.)
Pelargonium × hortorum L.H. Bailey (pro sp.)
Pelargonium × nervosum Sweet
et al.

Pelargonium /ˌpɛlɑrˈɡniəm/[1] 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.

History[edit]

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),[2] as pink or red, when to him it looked either pink or blue, having no relationship to red at all.[3]

Structure[edit]

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.[4]

Distribution[edit]

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. [5]

Cultivation[edit]

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.[6][7] They are easy to propagate from cuttings.[8]

Species, cultivars and hybrids[edit]

Regal group: Karl Offenstein
Ivy-leaved group: Pelargonium peltatum

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.[5]

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
    • Dwarf zonals
    • Miniature zonals
  • Angels
  • 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
  • Regals
  • Uniques
  • Formosum
  • Frutetorum hybrids
  • Stellars

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.

Scented-leaf pelargoniums[edit]

Cultivars are derived from a great number of species, amongst others P. graveolens. These include: Species

'Attar of Roses'

Cultivars

  • '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

Hybrids

  • 'Ginger' - P. × torento
  • 'Lemon Balm' - a hybrid: P. × melissinum
  • 'Lime' - a hybrid: (P. × nervosum)
  • 'Prince of Orange' - a hybrid: P. × citrosum

[5]

List of AGM cultivars[edit]

'Lady Plymouth'
'Mabel Gray'

The following is a selection of pelargoniums which have gained the Royal Horticultural Society's Award of Garden Merit:

  • 'Attar of Roses' (rose scented leaves, pink flowers)[11]
  • 'Citriodorum' (lemon scented leaves, rose pink flowers)[12]
  • 'Dolly Varden' (variegated leaves, scarlet flowers)[13]
  • 'Frank Headley' (cream vareigated leaves, salmon pink flowers)[14]
  • 'Fringed Aztec' (regal group - white & purple fringed flowers)[15]
  • 'Gemstone' (scented leaves, pink flowers)[16]
  • 'Grace Thomas' (lemon scented leaves, pale pink flowers)[17]
  • 'Joy' (pink & white frilled flowers)[18]
  • 'Lady Plymouth' (P. graveolens variegata - small mauve flowers)[19]
  • 'Lara Candy Dancer' (scented leaves, pale mauve flowers)[20]
  • 'Lara Starshine' (aromatic leaves, lilac flowers)[21]
  • 'L'Élégante' (ivy-leaved, trailing, white and purple flowers)[22]
  • 'Mabel Grey' (lemon-scented leaves, mauve flowers)[23]
  • 'Mrs Quilter' (bronze leaves, salmon pink flowers)[24]
  • 'Radula' (lemon & rose scented leaves, pink & purple flowers)[25]
  • 'Royal Oak' (balsam scented leaves, mauve flowers)[26]
  • 'Spanish Angel' (lilac & magenta flowers)[27]
  • 'Sweet Mimosa' (balsam-scented leaves, pale pink flowers)[28]
  • 'Tip Top Duet' (pink & wine-red flowers)[29]
  • P. tomentosum (peppermint-scented leaves, small white flowers)[30]
  • 'Voodoo' (crimson & black flowers)[31]

Usage[edit]

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.[citation needed] 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.[32]

Ecology[edit]

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. × hortorum). The phenomenon was first described in 1920, and subsequently confirmed.[33][34][35][36] 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.[37][38] Quisqualic acid is thought to mimic L-glutamic acid, which is a neurotransmitter in the insect neuromuscular junction and mammalian central nervous system.[39]

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 × hortorum was unattractive to pollinators in comparison to other selected garden plants such as Lavandula (lavender) and Origanum.[40]

Diseases[edit]

Herbal medicine[edit]

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.[32] P. sidoides along with Echinacea is used for bronchitis.[41] 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.[42] It is also used to balance the hormonal system, menstrual flow, and clean the body of toxins.[43][unreliable medical source?]

Image gallery[edit]

Notes[edit]

  1. ^ Sunset Western Garden Book, 1995:606–607
  2. ^ Hunt, D. M.; K. S. Dulai; J. K. Bowmaker; J. D. Mollon (1995). "The chemistry of John Dalton's color blindness". Science 267 (984-988). 
  3. ^ Dalton, John (1798). "Extraordinary facts relating to the vision of colours: with observations.". Memoirs of the Literary and Philosophical Society of Manchester 5: 28–45. 
  4. ^ Appell, Scott D. (2001). The Potted Garden: New plants and New approaches for container gardens.. p. [page needed]. ISBN 1889538221. 
  5. ^ a b c Sayre, James K. (2003). "Scented Geraniums or Pelargoniums". Bottlebrushpress.com. 
  6. ^ "thepags.org.uk". thepags.org.uk. Retrieved 2013-09-12. 
  7. ^ RHS A-Z encyclopedia of garden plants. United Kingdom: Dorling Kindersley. 2008. p. 1136. ISBN 1405332964. 
  8. ^ "Gardening - Gardening Guides - Techniques - Taking pelargonium cuttings". BBC. 1970-01-01. Retrieved 2013-09-12. 
  9. ^ Sweet, Robert (1822). Geraniaceae: The natural order of gerania, illustrated by coloured figures and descriptions; comprising the numerous and beautiful mule-varieties cultivated in the gardens of Great Britain, with directions for their treatment. Volume I. J. Ridgway. 
  10. ^ "Global Biodiversity Information Facility: Geranium ignescens". Data.gbif.org. 2007-02-22. Retrieved 2013-09-12. 
  11. ^ "Pelargonium 'Attar of Roses'". Royal Horticultural Society. 
  12. ^ "Pelargonium 'Citriodorum'". Royal Horticultural Society. 
  13. ^ "Pelargonium 'Dolly Varden'". Royal Horticultural Society. 
  14. ^ "Pelargonium 'Frank Headley'". Royal Horticultural Society. 
  15. ^ "Pelargonium 'Fringed Aztec'". Royal Horticultural Society. 
  16. ^ "Pelargonium 'Gemstone'". Royal Horticultural Society. 
  17. ^ "Pelargonium 'Grace Thomas'". Royal Horticultural Society. 
  18. ^ "Pelargonium 'Joy'". Royal Horticultural Society. 
  19. ^ "Pelargonium 'Lady Plymouth'". Royal Horticultural Society. 
  20. ^ "Pelargonium 'Lara Candy Dancer'". Royal Horticultural Society. 
  21. ^ "Pelargonium 'Lara Starshine'". Royal Horticultural Society. 
  22. ^ "Pelargonium 'L'Élégante'". Royal Horticultural Society. 
  23. ^ "Pelargonium 'Mabel Grey'". Royal Horticultural Society. 
  24. ^ "Pelargonium 'Mrs Quilter'". Royal Horticultural Society. 
  25. ^ "Pelargonium 'Radula'". Royal Horticultural Society. 
  26. ^ "Pelargonium 'Royal Oak'". Royal Horticultural Society. 
  27. ^ "Pelargonium 'Spanish Angel'". Royal Horticultural Society. 
  28. ^ "Pelargonium 'Sweet Mimosa'". Royal Horticultural Society. 
  29. ^ "Pelargonium 'Tip Top Duet'". Royal Horticultural Society. 
  30. ^ "Pelargonium P. tomentosum". Royal Horticultural Society. 
  31. ^ "Pelargonium 'Voodoo'". Royal Horticultural Society. 
  32. ^ a b "Pelargoniums - An Herb Society of America Fact Sheet". The Herb Society of America. 2006. Retrieved 20 December 2012. 
  33. ^ Davis, J.J. 1920. The green Japanese beetle. New Jersey Department of Agriculture Circular. 30: 33.
  34. ^ Ballou, C. H. 1929. Effects of geranium on the Japanese beetle. Journal of Economic Entomology. 22: 289-293.
  35. ^ Potter, D. A. and Held, D. W. 1999. Absence of food-aversion learning by a polyphagous scarab, Popillia japonica, following intoxication by geranium, Pelargonium x hortorum. Entomologia Experimentalis et Applicata. 91: 83-88.
  36. ^ Held, D. W. and Potter, D. A. 2003. Characterizing toxicity of Pelargonium spp. and two other reputedly toxic plant species to Japanese beetles (Coleoptera: Scarabaeidae). Environmental Entomology. 32: 873-880.
  37. ^ Geraniums and Begonias: New Research on Old Garden Favorites (the March 2010 issue of Agricultural Research magazine.)
  38. ^ Ranger, C.M.; Winter, R. E.; Singh, A. P.; Reding, M. E.; Frantz, J. M.; Locke, J. C.; Krause, C. R. (2011). "Rare excitatory amino acid from flowers of zonal geranium responsible for paralyzing the Japanese beetle". Proceedings of the National Academy of Sciences 108 (4): 1217–1221. doi:10.1073/pnas.1013497108. 
  39. ^ Usherwood, P. N. R. 1994. Insect glutamate receptors. Advances in Insect Biochemistry and Physiology. 24: 309-341.
  40. ^ "Quantifying variation among garden plants in attractiveness to bees and other flower-visiting insects". Functional Ecology. 2013. Retrieved 17 October 2013. 
  41. ^ "Pelargonium sidoides (African geranium)". WholeHealth Chicago. 
  42. ^ "Apple Geranium". Natural Medicinal Herbs. 
  43. ^ "Geranium". Herbs Guide. 

References[edit]

External links[edit]