Geranium Explained

Geranium is a genus of 422 species of annual, biennial, and perennial plants that are commonly known as geraniums or cranesbills. They are found throughout the temperate regions of the world and the mountains of the tropics, with the greatest diversity in the eastern part of the Mediterranean region.[1]

The palmately cleft leaves are broadly circular in form. The flowers have five petals and are coloured white, pink, purple, or blue, often with distinctive veining. Geraniums will grow in any soil as long as it is not waterlogged.[2] Propagation is by semiripe cuttings in summer, by seed, or by division in autumn or spring.[3]

Geraniums are eaten by the larvae of some Lepidoptera species including brown-tail, ghost moth, and mouse moth. At least several species of Geranium are gynodioecious.[4] [5] [6] The species Geranium viscosissimum (sticky geranium) is considered to be protocarnivorous.[7]

Name

The genus name is derived from Ancient Greek Greek, Ancient (to 1453);: γέρανος (géranos) 'crane'. The English name 'cranesbill' derives from the resemblance of the fruit capsule of some of the species to a crane's head and bill. The ovary portion forms the head and the prolonged stigma creates the appearance of a beak.[8] [9]

Description

The flowers are typically five-petaled and white to purple. The leaves are palmate divided into narrow, pointed segments.

The fruit capsule consists of five cells joined to a column produced from the centre of the flower. The cells form lobes which eventually separate, each containing one seed. When the fruit is ripe, the beak-like stigma springs open and casts the ovoid, streamlined seeds some distance, dispersing the seeds.[10]

Confusion with Pelargonium

Confusingly, "geranium" is also the common name of members of the genus Pelargonium, which are also in the family Geraniaceae and are widely grown as horticultural bedding plants. Linnaeus originally included all the species in one genus, Geranium, but they were later separated into two genera by Charles L’Héritier in 1789.[11] Other former members of the genus are now classified in Erodium, including the plants known as filarees in North America.[12]

The term "hardy geranium" is often applied to horticultural Geraniums to distinguish them from the Pelargoniums, which are not winter-hardy in temperate horticulture.[13] [14] However, not all Geranium species are winter-hardy (see below).[15]

The shape of the flowers offers one way of distinguishing between the two genera Geranium and Pelargonium. Geranium flowers have five very similar petals, and are thus radially symmetrical (actinomorphic), whereas Pelargonium (and also Erodium) flowers have two upper petals which are different from the three lower petals, so the flowers have a single plane of symmetry (zygomorphic).[16] [17]

Cultivation

A number of geranium species are cultivated for horticultural use and for pharmaceutical products. Some of the more commonly grown species include:

All the above species are perennials and generally winter-hardy plants, grown for their attractive flowers and foliage. They are long-lived and most have a mounding habit, with palmately lobed foliage. Some species have spreading rhizomes. They are normally grown in part shade to full sun, in well-draining but moisture retentive soils, rich in humus. Other perennial species grown for their flowers and foliage include: Geranium argenteum, G. eriostemon, G. farreri, G. nodosum, G. procurrens, G. pylzowianum, G. renardii, G. traversii, G. tuberosum, G. versicolor, G. wallichianum, and G. wlassovianum. Some of these are not winter-hardy in cold areas and are grown in specialized gardens like rock gardens. Geranium 'Johnson's Blue' is a hybrid between G. himalayense (southwestern China), with G. pratense (European meadow cranesbill).[18]

Cultivars

The following hybrid cultivars have gained the Royal Horticultural Society's Award of Garden Merit (other cultivars are dealt with under their species name - see above):-[19]

See also

Bibliography

External links

Notes and References

  1. Book: Allaby . Michael . The Dictionary of Science for Gardeners: 6000 Scientific Terms Explored and Explained . 26 August 2015 . Timber Press . 978-1-60469-483-3 . 5 April 2024 . en.
  2. Book: Tibballs, Geoff . 100 Plants That Won't Die in Your Garden . 2017-03-09 . Little, Brown Book Group . 978-1-4721-3800-2 . en.
  3. Book: Brickell, Christopher . American Horticultural Society Encyclopedia of Plants and Flowers . 2011-08-15 . Penguin . 978-0-7566-7508-0 . en.
  4. Hessing, M.B. 1989. Variation in self-fertility and floral characters of Geranium caespitosum (Geraniaceae) along an elevational gradient. Plant Systematics and Evolution 166:225-241.
  5. Van Etten and Chang 2014. Frequency-dependent pollinator discrimination acts against female plants in the gynodioecious Geranium maculatum Annals of Botany 114:1769–1778
  6. 10.1016/j.flora.2016.11.007. Prolonged stigma and flower lifespan in females of the gynodioecious plant Geranium sylvaticum. Flora. 226. 72–81. 2017. Elzinga. Jelmer A.. Varga. Sandra. 2017FMDFE.226...72E. 85558947.
  7. Spomer . George G. . 1999 . Evidence of Protocarnivorous Capabilities in Geranium viscosissimum and Potentilla arguta and Other Sticky Plants . International Journal of Plant Sciences . en . 160 . 1 . 98–101 . 10.1086/314109 . 1058-5893.
  8. Book: Taylor, Ronald J.. Sagebrush Country: A Wildflower Sanctuary. Mountain Press Pub. Co. 1994. 0-87842-280-3. rev.. Missoula, MT. 62. en. 25708726. 1992.
  9. Web site: Geranium homeanum . Australian Plants Society . 5 April 2024 . en-AU . 17 January 2024.
  10. Stamp . Nancy E. . Lucas . Jeffrey R. . 1983 . Ecological Correlates of Explosive Seed Dispersal . Oecologia . 59 . 2/3 . 272–278 . 10.1007/BF00378848 . 4217097 . 28310244 . 1983Oecol..59..272S . 0029-8549.
  11. Book: Lis-Balchin, Maria . Geranium and Pelargonium: History of Nomenclature, Usage and Cultivation . 2002-10-03 . CRC Press . 978-0-203-21653-8 . en.
  12. Book: Armitage, Allan M. . Herbaceous Perennial Plants: A Treatise on their Identification, Culture, and Garden Attributes . 2008-05-01 . Quarto Publishing Group USA . 978-1-61058-380-0 . en.
  13. Book: Parer . Robin . The Plant Lover's Guide to Hardy Geraniums . 20 April 2016 . Timber Press . 978-1-60469-418-5 . en.
  14. Web site: Geranium or Pelargonium? Let's Stop the Confusion . 2024-04-05 . Laidback Gardener . en-US.
  15. Web site: Geranium Climate: Sun and Temperature . geraniumpage.com.
  16. Web site: Chris . 2015-11-28 . Pelargonium incarnatum - Is it a Geranium? No it's a Pelargonium . 2024-04-05 . Phillipskop Mountain Reserve . en-GB.
  17. Web site: 2022-11-24 . Tom Karwin, On Gardening Visiting the Geranium family . 2024-04-05 . Santa Cruz Sentinel . en-US.
  18. Web site: Paghat's Garden . Paghat.com . 2013-09-17.
  19. Web site: AGM Plants - Ornamental . July 2017 . 39 . Royal Horticultural Society . 27 February 2018.
  20. Web site: RHS Plant Selector Geranium 'Ann Folkard' AGM / RHS Gardening . Apps.rhs.org.uk . 5 April 2020.
  21. Web site: RHS Plant Selector Geranium × oxonianum 'A.T. Johnson' AGM / RHS Gardening . Apps.rhs.org.uk . 5 April 2020.
  22. Web site: Geranium (Cinereum Group) 'Ballerina' . RHS . 11 July 2020.
  23. Web site: RHS Plantfinder - Geranium 'Blue Cloud' . 1 March 2018.
  24. Web site: Geranium Blue Sunrise='Blogold' (PBR) . RHS . 11 July 2020.
  25. Web site: Geranium 'Brookside' . RHS . 11 July 2020.
  26. Web site: RHS Plantfinder - Geranium 'Danny Boy' . 2 March 2018.
  27. Web site: RHS Plant Selector Geranium 'Dilys' AGM / RHS Gardening . Apps.rhs.org.uk . 2013-09-17.
  28. Web site: RHS Plantfinder - G. × lindavicum 'Gypsy' . 1 March 2018.
  29. Web site: Geranium 'Ivan' . RHS . 11 July 2020.
  30. Web site: RHS Plant Selector Geranium 'Mavis Simpson' AGM / RHS Gardening . Apps.rhs.org.uk . 2013-09-17.
  31. Web site: Geranium 'Nimbus' . RHS . 11 July 2020.
  32. Web site: RHS Plant Selector Geranium 'Orion' AGM / RHS Gardening . Apps.rhs.org.uk . 2013-09-17.
  33. Web site: RHS Plantfinder - Geranium Pattricia = 'Brempat' . 2 March 2018.
  34. Web site: Geranium Rothbury Gem = 'Gerfos' . RHS . 14 July 2020.
  35. Web site: RHS Plant Selector Geranium ROZANNE= 'Gerwat' PBR AGM / RHS Gardening . Apps.rhs.org.uk . 5 April 2020.
  36. Web site: RHS Plantfinder - Geranium × riversleainum 'Russell Prichard' . 2 March 2018.
  37. Web site: Geranium 'Sirak' . RHS . 14 July 2020.
  38. Web site: Geranium × oxonianum 'Wageningen' . RHS . 11 July 2020.
  39. Web site: RHS Plant Selector Results / RHS Gardening . Apps.rhs.org.uk . 5 April 2020.

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