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Geranium

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This article is about the botanical genus called Geranium. For the summer bedding plants often called "geranium", see Pelargonium. For other uses, see Geranium (disambiguation).
Not to be confused with germanium.

Geranium
Geranium dissectum
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Geraniales
Family: Geraniaceae
Genus: Geranium
L.
Species

See list.

Geranium is a genus of 422 species of flowering annual, biennial, and perennial plants that are commonly known as the cranesbills. They are found throughout the temperate regions of the world and the mountains of the tropics, but mostly in the eastern part of the Mediterranean region.

The long, 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. Propagation is by semiripe cuttings in summer, by seed, or by division in autumn or spring.

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.[1][2][3] The species Geranium viscosissimum (sticky geranium) is considered to be protocarnivorous.

Description

The genus name is derived from the Greek γέρανος (géranos) or γερανός (geranós) ‘crane’. The English name ‘cranesbill’ derives from the appearance of the fruit capsule of some of the species. Species in the genus Geranium have a distinctive mechanism for seed dispersal. This consists of a beak-like column which springs open when ripe and casts the seeds some distance. The fruit capsule consists of five cells, each containing one seed, joined to a column produced from the centre of the old flower. The common name ‘cranesbill’ comes from the shape of the unsprung column, which in some species is long and looks like the bill of a crane. However, many species in this genus do not have a long beak-like column.

Confusion with Pelargonium

Showing the "bill" and seed dispersal mechanism of Geranium pratense

Confusingly, "geranium" is also the common name of members of the genus Pelargonium, which are also in the Geraniaceae family 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. Other former members of the genus are now classified in Erodium, including the plants known as filarees in North America.

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

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).

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.[4] Other perennial species grown for their flowers and foliage include: G. 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.[5] Geranium 'Johnson's Blue' is a hybrid between G. himalayense (southwestern China), with G. pratense (European meadow cranesbill).[6]

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):-[7]

  • 'Ann Folkard'[8]
  • ’Blue Cloud’[9]
  • ’Danny Boy’[10]
  • 'Dilys'[11]
  • ’Gypsy’ (G. × lindavicum)[12]
  • 'Johnson's Blue'[13]
  • 'Mavis Simpson'[14]
  • 'Orion'[15]
  • Patricia = ‘Brempat’[16]
  • 'Rozanne'[17]
  • ’Russell Prichard’[18]
  • 'A. T. Johnson' (G. × oxonianum)[19]
  • 'Wargrave pink' (G. × oxonianum)[20]

See also

Wikispecies has information related to Geranium.
Wikimedia Commons has media related to Geranium.

References

  1. ^ 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.
  2. ^ Van Etten and Chang 2014. Frequency-dependent pollinator discrimination acts against female plants in the gynodioecious Geranium maculatum Annals of Botany 114:1769–1778
  3. ^ Elzinga, J.A., and Varga, S. 2017. Prolonged stigma and flower lifespan in females of the gynodioecious plant Geranium sylvaticum. Flora 226:72-81
  4. ^ Phillips, Ellen; Colston Burrell, C. (1993), Rodale's illustrated encyclopedia of perennials, Emmaus, Pa.: Rodale Press, pp. 373–76, ISBN 0-87596-570-9
  5. ^ Jelitto, Leo; Schacht, Wilhelm; Epp, Translated by Michael E.; John Philip Baumgardt, Technical Editor (1990), Hardy herbaceous perennials, vol. 1, Portland, Or.: Timber Press, pp. 260–64, ISBN 0-88192-159-9 {{citation}}: |first4= has generic name (help)
  6. ^ "Paghat's Garden". Paghat.com. Retrieved 2013-09-17.
  7. ^ "AGM Plants - Ornamental" (PDF). Royal Horticultural Society. July 2017. p. 39. Retrieved 27 February 2018.
  8. ^ "RHS Plant Selector Geranium 'Ann Folkard' AGM / RHS Gardening". Apps.rhs.org.uk. Retrieved 2013-09-17.
  9. ^ "RHS Plantfinder - Geranium 'Blue Cloud'". Retrieved 1 March 2018.
  10. ^ "RHS Plantfinder - Geranium 'Danny Boy'". Retrieved 2 March 2018.
  11. ^ "RHS Plant Selector Geranium 'Dilys' AGM / RHS Gardening". Apps.rhs.org.uk. Retrieved 2013-09-17.
  12. ^ "RHS Plantfinder - G. × lindavicum 'Gypsy'". Retrieved 1 March 2018.
  13. ^ "RHS Plant Selector Geranium 'Johnson's Blue' / RHS Gardening". Apps.rhs.org.uk. Retrieved 2013-09-17.
  14. ^ "RHS Plant Selector Geranium 'Mavis Simpson' AGM / RHS Gardening". Apps.rhs.org.uk. Retrieved 2013-09-17.
  15. ^ "RHS Plant Selector Geranium 'Orion' AGM / RHS Gardening". Apps.rhs.org.uk. Retrieved 2013-09-17.
  16. ^ "RHS Plantfinder - Geranium Pattricia = 'Brempat'". Retrieved 2 March 2018.
  17. ^ "RHS Plant Selector Geranium ROZANNE 'Gerwat' PBR AGM / RHS Gardening". Apps.rhs.org.uk. Retrieved 2013-09-17.
  18. ^ "RHS Plantfinder - Geranium × riversleainum 'Russell Prichard'". Retrieved 2 March 2018.
  19. ^ "RHS Plant Selector Geranium × oxonianum 'A.T. Johnson' AGM / RHS Gardening". Apps.rhs.org.uk. Retrieved 2013-09-17.
  20. ^ "RHS Plant Selector Results / RHS Gardening". Apps.rhs.org.uk. Retrieved 2013-09-17.

Bibliography

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