Saxifraga Explained

Saxifraga is the largest genus in the family Saxifragaceae, containing about 473 species of holarctic perennial plants, known as saxifrages[1] or rockfoils.[2] The Latin word saxifraga means literally "stone-breaker", from Latin Latin: [[:wikt:saxum|saxum]] ("rock" or "stone") + Latin: [[:wikt:frangere|frangere]] ("to break"). It is usually thought to indicate a medicinal use for treatment of urinary calculi (known as kidney or bladder stones), rather than breaking rocks apart.[1] [3]

Description

Most saxifrages are small perennial, biennial (e.g. S. adscendens) or annual (e.g. S. tridactylites) herbaceous plants whose basal or cauline leaves grow close to the ground, often in a rosette. The leaves typically have a more or less incised margin; they may be succulent, needle-like and/or hairy, reducing evaporation.

The inflorescence or single flower clusters rise above the main plant body on naked stalks. The small actinomorphic hermaphrodite flowers have five petals and sepals and are usually white, but red to yellow in some species. Stamens, usually 10, rarely 8, insert at the junction of the floral tube and ovary wall, with filaments subulate or clavate. As in other primitive eudicots, some of the 5 or 10 stamens may appear petal-like. and it lives in tundral ecosystems.

Taxonomy

A genus of about 473 species. The former monotypic genus Saxifragella has been submersed within Saxifraga, the largest genus in Saxifragaceae, as Saxifraga bicuspidata. Also the genus Saxifragopsis (strawberry saxifrage) was previously included in Saxifraga.[4]

Subdivision

Based on morphological criteria, up to 15 sections were recognised. Subsequent molecular phylogenetic studies reduced this to 13 sections with 9 subsections. The former sections Micranthes and Merkianae are more closely related to the Boykinia and Heuchera clades. Modern floras separate these groups as the genus Micranthes.[5]

The thirteen sections (with subsections) are:

Selected species

See main article: List of ''Saxifraga'' species.

Formerly placed here

Plants formerly placed in Saxifraga are mainly but not exclusively Saxifragaceae. They include:

Other "saxifragous" plants

Several plant genera have names referring to saxifrages, although they might not be close relatives of Saxifraga. They include:

Some plants refer to Saxifraga in their generic names or specific epithets, either because they are also "rock-breaking" or because they resemble members of the saxifrage genus:

Ecology

Saxifrages are typical inhabitants of Arctic–alpine ecosystems, and are hardly ever found outside the temperate parts of the Northern Hemisphere; most members of this genus are found in subarctic climates. A good number of species grow in glacial habitats, such as S. biflora which can be found some above sea level in the Alps, or the East Greenland saxifrage (S. nathorstii). The genus is also abundant in the Eastern and Western Himalayan alpine shrub and meadows. Though the archetypal saxifrage is a small plant huddling between rocks high up on a mountain, many species do not occur in such a habitat and are larger (though still rather delicate) plants found on wet meadows.

Various Saxifraga species are used as food plants by the caterpillars of some butterflies and moths, such as the Phoebus Apollo (Parnassius phoebus).[9]

Charles Darwin – erroneously believing Saxifraga to be allied to the sundew family (Droseraceae) – suspected the sticky-leaved round-leaved saxifrage (S. rotundifolia), rue-leaved saxifrage (S. tridactylites) and Pyrenean saxifrage (S. umbrosa) to be protocarnivorous plants, and conducted some experiments whose results supported his observations,[10] but the matter has apparently not been studied since his time.

Cultivation

Numerous species and cultivars of saxifrage are cultivated as ornamental garden plants, valued particularly as groundcover or as cushion plants in rock gardens and alpine gardens. Many require alkaline or neutral soil to thrive.[11]

S. × urbium (London pride), a hybrid between Pyrenean saxifrage (S. umbrosa) and St. Patrick's cabbage (S. spathularis), is commonly grown as an ornamental plant.[1] Another horticultural hybrid is Robertsoniana saxifrage (S. × geum), derived from kidney saxifrage (S. hirsuta) and Pyrenean saxifrage. Some wild species are also used in gardening. Cambridge University Botanic Garden hosts the United Kingdom's national collection of saxifrages.[1]

Award of Garden Merit

The following species and cultivars have gained the Royal Horticultural Society's Award of Garden Merit:-[12]

Uses

The leaves of some saxifrage species, such as creeping saxifrage (S. stolonifera) and S. pensylvanica,[43] are edible. The former is a food in Korea[44] and Japan. The flowers of purple saxifrage (S. oppositifolia) are eaten in Nunavut, Canada and the leaves and stems brewed as a tea.[45]

Species are also used in traditional medicine, such as creeping saxifrage in East Asia[46] and round-leaved saxifrage (S. rotundifolia) in Europe.[47]

Two species—purple saxifrage and creeping saxifrage—are popular floral emblems. They are official flowers for:

Bibliography

Books
Articles
Websites
Floras

Notes and References

  1. Web site: Saxifraga . National Plant Collections . . October 3, 2011.
  2. Roger Spencer, ed. Horticultural Flora of South-Eastern Australia. UNSW Press, 2002. p. 81.
  3. Book: D. A. Webb . R. J. Gornall . amp . 1989 . Saxifrages of Europe . Christopher Helm . 0-7470-3407-9 . 19.
  4. Web site: . February 9, 2005 . . Saxifraga L. . January 20, 2009.
  5. http://www.efloras.org/florataxon.aspx?flora_id=2&taxon_id=10800 Flora of China
  6. Umberto Quattrocchi. CRC World Dictionary of Plant Names: Common Names, Scientific Names, Eponyms. Synonyms, and Etymology. CRC Press, 1999. p.2395-2396.
  7. Knaben . G. . Saxifraga osloensis n. sp., a tetraploid species of the Tridactylites section . Nytt Magasin for Botanikk . 1934 . 117–138.
  8. Reader's Digest Nature Lover's Library Wild Flowers of Britain, page 192, published 1988
  9. Book: Ivo Novák . 1980 . A Field Guide in Colour to Butterflies and Moths . . 0-7064-1293-1.
  10. Book: Charles Darwin . Charles Darwin . 1875 . Drosophyllum – Roridula – Byblis – glandular hairs of other plants – concluding remarks on the Droseraceae . Insectivorous Plants . 1st . 332–367 . J. Murray . London .
  11. Book: RHS A-Z encyclopedia of garden plants . 2008 . Dorling Kindersley . United Kingdom . 978-1405332965 . 1136.
  12. Web site: AGM Plants - Ornamental . July 2017 . 95 . Royal Horticultural Society . 1 November 2018.
  13. Web site: RHS Plantfinder - Saxifraga 'Angelina Johnson' . 1 November 2018.
  14. Web site: RHS Plantfinder - Saxifraga 'Blackberry and Apple Pie' . 1 November 2018.
  15. Web site: RHS Plant Selector - Saxifraga callosa . 5 March 2021.
  16. Web site: RHS Plantfinder - Saxifraga 'Conwy Snow' . 1 November 2018.
  17. Web site: RHS Plantfinder - Saxifraga 'Coolock Kate' . 1 November 2018.
  18. Web site: RHS Plantfinder - Saxifraga 'Cumulus' . 1 November 2018.
  19. Web site: RHS Plant Selector - Saxifraga fortunei . 5 March 2021.
  20. Web site: RHS Plantfinder - Saxifraga 'Gregor Mendel' (× fortunei) . 1 November 2018.
  21. Web site: RHS Plantfinder - Saxifraga 'Lagraveana' . 1 November 2018.
  22. Web site: RHS Plant Selector - Saxifraga 'Lutea' . 2 June 2013.
  23. Web site: RHS Plant Selector - Saxifraga 'Minor' . 5 March 2021.
  24. Web site: RHS Plantfinder - Saxifraga 'Moe' . 1 November 2018.
  25. Web site: RHS Plantfinder - Saxifraga 'Monarch' . 1 November 2018.
  26. Web site: RHS Plantfinder - Saxifraga 'Mount Nachi' . 1 November 2018.
  27. Web site: RHS Plantfinder - Saxifraga 'Peach Melba' . 1 November 2018.
  28. Web site: RHS Plantfinder - Saxifraga (Silver Farreri Group) 'Reginald Farrer' . 1 November 2018.
  29. Web site: RHS Plantfinder - Saxifraga 'Rokujo' (fortunei) . 1 November 2018.
  30. Web site: RHS Plant Selector - Saxifraga 'Rosea' . 5 March 2021.
  31. Web site: RHS Plantfinder - Saxifraga 'Shiranami' . 1 November 2018.
  32. Web site: RHS Plantfinder - Saxifraga (Southside Seedling Group) 'Slack's Ruby Southside' . 1 November 2018.
  33. Web site: RHS Plantfinder - Saxifraga (Silver Farreri Group) 'Snowflake' . 1 November 2018.
  34. Web site: RHS Plantfinder - (Southside seedling Group) 'Southside Star' . 1 November 2018.
  35. Web site: RHS Plant Selector - Saxifraga stolonifera . 5 March 2021.
  36. Web site: RHS Plantfinder - Saxifraga 'Sue Drew' . 1 November 2018.
  37. Web site: RHS Plantfinder - Saxifraga ='Toujya' . 1 November 2018.
  38. Web site: RHS Plant Selector - Saxifraga 'Theoden' . 5 March 2021.
  39. Web site: RHS Plant Selector - Saxifraga 'Tumbling Waters' . 5 March 2021.
  40. Web site: RHS Plant Selector - Saxifraga × urbium . 8 March 2021.
  41. Web site: RHS Plantfinder - Saxifraga 'Venetia' (paniculata) . 1 November 2018.
  42. Web site: RHS Plantfinder - Saxifraga 'Whitehill' . 1 November 2018.
  43. Book: Niering . William A. . The Audubon Society Field Guide to North American Wildflowers, Eastern Region . Olmstead . Nancy C. . Knopf . 1985 . 0-394-50432-1 . 780 . William Niering. 1979.
  44. Chon . Sang-Uk . Heo . Buk-Gu . Park . Yong-Seo . Cho . Ja-Yong . Gorinstein . Shela . 2008 . Characteristics of the leaf parts of some traditional Korean salad plants used for food . Journal of the Science of Food and Agriculture . en . 88 . 11 . 1963–1968 . 10.1002/jsfa.3304 . 2008JSFA...88.1963C . 1097-0010.
  45. http://www.assembly.nu.ca/about-legislative-assembly/official-flower-nunavut Official Flower of Nunavut
  46. Book: Ji-xian Guo, Ki Sung Chung, Paul Pui-hay But, Takeatsu Kimura . International Collation Of Traditional And Folk Medicine, Vol 2: Northeast Asia Part 2 . World Scientific Publishing Company . 1996 . 65.
  47. Book: Ethnobotany and Biocultural Diversities in the Balkans . Springer . 2014 . Pieroni . Andrea . New York . Quave . Cassandra L..
  48. Web site: 2011 . The Official Flower of Nunavut: Purple Saxifrage . July 31, 2011 . Legislative Assembly of Nunavut.
  49. http://www.plantlife.org.uk/uk/plantlife-discovering-plants-county-flowers.html County flowers in Britain
  50. Web site: City flower, bird and tree . 17 June 2021 . City of Tsukuba . Japanese.

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