Taraxacum

"Dandelion" redirects here. It may refer to any of the genus Taraxacum or specifically to Taraxacum officinale. For similar plants, see False dandelion. For other uses, see Dandelion (disambiguation)
Dandelion
A dandelion flower head composed of numerous small florets (top). The seed head is shown below it.
Scientific classification
Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Asterids
Order: Asterales
Family: Asteraceae
Subfamily: Cichorioideae
Tribe: Cichorieae
Subtribe: Crepidinae
Genus: Taraxacum
F. H. Wigg.
Type species
Taraxacum officinale [1]
F. H. Wigg.

Taraxacum (/təˈræksəkᵿm/) is a large genus of flowering plants in the family Asteraceae which consists of species commonly known as dandelion. They are native to Eurasia and North America, but the two commonplace species worldwide, T. officinale and T. erythrospermum, were imports from Europe that now propagate as wildflowers.[2] Both species are edible in their entirety.[3] The common name dandelion (/ˈdændᵻlaɪ.ən/ DAN-di-ly-ən, from French dent-de-lion, meaning "lion's tooth") is given to members of the genus. Like other members of the Asteraceae family, they have very small flowers collected together into a composite flower head. Each single flower in a head is called a floret. Many Taraxacum species produce seeds asexually by apomixis, where the seeds are produced without pollination, resulting in offspring that are genetically identical to the parent plant.[4]

Description

The species of Taraxacum are tap-rooted, perennial, herbaceous plants, native to temperate areas of the Northern Hemisphere. The genus contains many species which usually (or in the case of triploids, obligately) reproduce by apomixis, resulting in many local populations and endemism. In the British Isles alone, 234 microspecies are recognised in 9 loosely defined sections, of which 40 are "probably endemic".[5]

In general, the leaves are 5–25 cm long or longer, simple, lobed, and form a basal rosette above the central taproot. The flower heads are yellow to orange coloured, and are open in the daytime, but closed at night. The heads are borne singly on a hollow stem (scape) that is usually leafless and rises 1–10 cm or more[2] above the leaves. Stems and leaves exude a white, milky latex when broken. A rosette may produce several flowering stems at a time. The flower heads are 2–5 cm in diameter and consist entirely of ray florets. The flower heads mature into spherical seed heads called blowballs[6] or clocks (in both British and American English)[7][8][9][10] containing many single-seeded fruits called achenes. Each achene is attached to a pappus of fine hairs, which enable wind-aided dispersal over long distances.

The flower head is surrounded by bracts (sometimes mistakenly called sepals) in two series. The inner bracts are erect until the seeds mature, then flex downward to allow the seeds to disperse. The outer bracts are often reflexed downward, but remain appressed in plants of the sections Palustria and Spectabilia. Some species drop the parachute from the achenes; the hair-like parachutes are called pappus, and they are modified sepals. Between the pappus and the achene is a stalk called a beak, which elongates as the fruit matures. The beak breaks off from the achene quite easily, separating the seed from the parachute.

Seed dispersal

Segment of pappus fiber showing barbs

A number of species of Taraxacum are seed-dispersed ruderals that rapidly colonize disturbed soil, especially the common dandelion (T. officinale), which has been introduced over much of the temperate world. After flowering is finished, the dandelion flower head dries out for a day or two. The dried petals and stamens drop off, the bracts reflex (curve backwards), and the parachute ball opens into a full sphere.

False dandelions

Hawksbeard flower heads and ripe seeds are sometimes confused with dandelions.

Many similar plants in the Asteraceae family with yellow flowers are sometimes known as false dandelions. Dandelions are very similar to catsears (Hypochaeris). Both plants carry similar flowers, which form into windborne seeds. However, dandelion flowers are borne singly on unbranched, hairless and leafless, hollow stems, while catsear flowering stems are branched, solid, and carry bracts. Both plants have a basal rosette of leaves and a central taproot. However, the leaves of dandelions are smooth or glabrous, whereas those of catsears are coarsely hairy.

Early-flowering dandelions may be distinguished from coltsfoot (Tussilago farfara) by their basal rosette of leaves, their lack of disc florets, and the absence of scales on the flowering stem.[11]

Other plants with superficially similar flowers include hawkweeds (Hieracium) and hawksbeards (Crepis). These are readily distinguished by branched flowering stems, which are usually hairy and bear leaves.

Classification

The genus is taxonomically complex, with some botanists dividing the group into about 34 macrospecies, and about 2000 microspecies;[12] about 235 apomictic and polyploid microspecies have been recorded in Great Britain and Ireland.[13] Some botanists take a much narrower view and only accept a total of about 60 species.[12]

Selected species

T. albidum

T. albidum
T. californicum

T. californicum
T. japonicum

T. japonicum
T. laevigatum

T. laevigatum
T. officinale

T. officinale
T. platycarpum

T. platycarpum

Cultivars

History

Dandelions are thought to have evolved about 30 million years ago in Eurasia.[18] They have been used by humans for food and as an herb for much of recorded history.[19]

Names

Leaf resemblance to lion tooth

The Latin name Taraxacum originates in medieval Persian writings on pharmacy. The Persian scientist Al-Razi around 900 AD wrote "the tarashaquq is like chicory". The Persian scientist and philosopher Ibn Sīnā around 1000 AD wrote a book chapter on Taraxacum. Gerard of Cremona, in translating Arabic to Latin around 1170, spelled it tarasacon.[20]

The English name, dandelion, is a corruption of the French dent de lion[21] meaning "lion's tooth", referring to the coarsely toothed leaves. The plant is also known as blowball, cankerwort, doon-head-clock, witch's gowan, milk witch, lion's-tooth, yellow-gowan, Irish daisy, monks-head, priest's-crown, and puff-ball;[22] other common names include faceclock, pee-a-bed, wet-a-bed,[23] swine's snout,[24] white endive, and wild endive.[25]

The English folk name "piss-a-bed" (and indeed the equivalent contemporary French pissenlit) refers to the strong diuretic effect of the plant's roots.[26] In various northeastern Italian dialects, the plant is known as pisacan ("dog pisses"), because they are found at the side of pavements.[27]

In Swedish, it is called maskros (worm rose) after the small insects (thrips) usually present in the flowers.[28] In Finnish and Estonian, the names (voikukka, võilill) translate as butter flower, due to the color of the flower. In Lithuanian, it is known as "Pienė", meaning "milky", because of the white liquid that is produced when the stems are cut. The Welsh (dant-y-llew), German (Löwenzahn), Norwegian (løvetann) and Spanish (diente de león) names mean the same as the French and the English names.

Properties

Edibility

Dandelions are found on all continents and have been gathered for food since prehistory, but the varieties cultivated for consumption are mainly native to Eurasia. A perennial plant, its leaves will grow back if the taproot is left intact. To make leaves more palatable, they are often blanched to remove bitterness,[19] or sauteed in the same way as spinach.[29] Dandelion leaves and buds have been a part of traditional Kashmiri, Slovenian, Sephardic, Chinese, and Korean cuisines. In Crete, the leaves of a variety called 'Mari' (Μαρί), 'Mariaki' (Μαριάκι), or 'Koproradiko' (Κοπροράδικο) are eaten by locals, either raw or boiled, in salads. T. megalorhizon, a species endemic to Crete, is eaten in the same way; it is found only at high altitudes (1000 to 1600 m) and in fallow sites, and is called pentaramia (πενταράμια) or agrioradiko (αγριοράδικο).[30]

The flower petals, along with other ingredients, usually including citrus, are used to make dandelion wine. The ground, roasted roots can be used as a caffeine-free dandelion coffee.[31] Dandelion was also traditionally used to make the traditional British soft drink dandelion and burdock, and is one of the ingredients of root beer. Also, dandelions were once delicacies eaten by the Victorian gentry, mostly in salads and sandwiches.

Dandelion leaves contain abundant vitamins and minerals, especially vitamins A, C, and K, and are good sources of calcium, potassium, iron, and manganese.[32]

Medicinal uses

Historically, dandelion was prized for a variety of medicinal properties, and it contains a number of pharmacologically active compounds.[33] Dandelion is used as a herbal remedy in Europe, North America, and China.[33] It has been used in herbal medicine to treat infections, bile and liver problems,[33] and as a diuretic.[33]

Food for wildlife

Taraxacum seeds are an important food source for certain birds.[34]

Dandelions are also important plants for Northern Hemisphere bees, providing an important source of nectar and pollen early in the season.[35] Dandelions are used as food plants by the larvae of some species of Lepidoptera (butterflies and moths). They are also used as a source of nectar by the pearl-bordered fritillary (Boloria euphrosyne), one of the earliest emerging butterflies in the spring.

Benefits to gardeners

The dandelion plant is a beneficial weed, with a wide range of uses, and is even a good companion plant for gardening. Its taproot will bring up nutrients for shallower-rooting plants, and add minerals and nitrogen to soil. It is also known to attract pollinating insects and release ethylene gas which helps fruit to ripen.[36]

Cultural importance

Four dandelion flowers are the emblem of White Sulphur Springs, West Virginia.[37] The citizens celebrate spring with an annual Dandelion Festival.

The dandelion is the official flower of the University of Rochester and "Dandelion Yellow" is one of the school's official colors. "The Dandelion Yellow" is an official University of Rochester song.[38]

Dangers

Dandelion pollen may cause allergic reactions when eaten, or adverse skin reactions in sensitive individuals. Contact dermatitis after handling has also been reported, probably from the latex in the stems and leaves.[39] Due to its high potassium level, dandelion can also increase the risk of hyperkalemia when taken with potassium-sparing diuretics.[40]

As a noxious weed

The species T. officinale is listed as a noxious weed in some jurisdictions,[41] and is considered to be a nuisance in residential and recreational lawns in North America.[42] It is also an important weed in agriculture and causes significant economic damage because of its infestation in many crops worldwide.[41]

As source of natural rubber

Dandelions secrete latex when the tissues are cut or broken, yet in the wild type, the latex content is low and varies greatly. Using modern cultivation methods and optimization techniques, scientists in the Fraunhofer Institute for Molecular Biology and Applied Ecology (IME) in Germany developed a cultivar that is suitable for commercial production of natural rubber. The latex produced exhibits the same quality as the natural rubber from rubber trees.[43] In collaboration with Continental Tires, IME is building a pilot facility. As of May 2014, the first prototype test tires made with blends from dandelion-rubber are scheduled to be tested on public roads over the next few years.[44]

See also

References

  1. ↑ Adrian John Richards (1985). "Sectional nomenclature in Taraxacum (Asteraceae)". Taxon. 34 (4): 633–644. JSTOR 1222201.
  2. 1 2 Luc Brouillet. "Taraxacum F. H. Wiggers, Prim. Fl. Holsat. 56. 1780". Flora of North America.
  3. ↑ "Wild About Dandelions". Mother Earth News.
  4. ↑ J. Doll & T. Trower. "Dandelion". WeedScience. University of Wisconsin. Archived from the original on 22 October 2008.
  5. ↑ Stace, C.A. (2010). New flora of the British isles (Third ed.). Cambridge, U.K.: Cambridge University Press. p. 712. ISBN 9780521707725.
  6. ↑ "blowball". McGraw-Hill Dictionary of Scientific & Technical Terms, 6E. The McGraw-Hill Companies, Inc. 2003. Retrieved 26 January 2013.
  7. ↑ "Blowball" entry, Collins Dictionary
  8. ↑ "Blowball", InfoPlease Dictionary
  9. ↑ "dandelion clock - Definition from Longman English Dictionary Online". Jonas: Mosby's Dictionary of Complementary and Alternative Medicine. (c) 2005, Elsevier. Ldoceonline.com. Retrieved 2010-07-03.
  10. ↑ "Clock" entry, American Heritage Dictionary
  11. ↑ Blamey, M.; Fitter, R.; Fitter, A (2003). Wild flowers of Britain and Ireland: The Complete Guide to the British and Irish Flora. London: A & C Black. p. 274. ISBN 978-1408179505.
  12. 1 2 A. J. Richards (1970). "Eutriploid facultative agamospermy in Taraxacum". New Phytologist. 69 (3): 761–774. doi:10.1111/j.1469-8137.1970.tb02461.x. JSTOR 2430530.
  13. ↑ Richards, A.J. (1997). Dandelions of Great Britain and Ireland (Handbooks for Field Identification). BSBI Publications. p. 330. ISBN 978-0-901158-25-3.
  14. ↑ "Alberta Biodiversity Monitoring Institute - Taraxacum ceratophorum". Retrieved 2013-08-29.
  15. ↑ "Flora of North America". Efloras.org. Retrieved 2012-08-29.
  16. ↑ "Plants for a future: Taraxacum kok-saghiz".
  17. ↑ "Dandelion". Fondation Louis Bonduelle.
  18. ↑ "Gardening in Western Washington: Dandelions". Gardening.wsu.edu. 2003-05-04. Retrieved 2012-08-29.
  19. 1 2 McGee, Harold (2004). "A survey of common vegetables". On Food and Cooking: the science and lore of the kitchen. New York: Scribner. p. 320. ISBN 0-684-80001-2.
  20. ↑ Reported in An Etymological Dictionary of the English Language, by Walter W. Skeat (1888) (Downloadable at Archive.org). In An Etymology Dictionary of Modern English by Ernest Weekley (1921) it is reported that Arabic tarashaqun is derivable in turn from Persian talkh chakok, bitter herb (Downloadable at Archive.org).
  21. ↑ S. Potter & L. Sargent (1973) Pedigree: essays on the etymology of words from nature. Collins New Naturalist series Volume 56
  22. ↑ Britton, N. F.; Brown, Addison (1970). An illustrated flora of the northern United States and Canada: from Newfoundland to the parallel of the southern boundary of Virginia, and from the Atlantic Ocean westward to the 102d meridian. New York: Dover Publications. p. 315. ISBN 0-486-22644-1.
  23. ↑ "Common Dandelion_Family: Asteraceae" (PDF).
  24. ↑ Loewer, Peter (2001). Solving weed problems. Guilford, Conn.: Lyons Press. p. 210. ISBN 1-58574-274-0.
  25. ↑ "Dandelion clock". TheFreeDictionary.com.
  26. ↑ Taylor, Joseph (1819). Antiquitates curiosae: the etymology of many remarkable old sayings, proverbs and singular customs explained by Joseph Taylor (2nd ed.). T&J Allman. p. 97. Retrieved 25 May 2010.
  27. ↑ Anon. "Dandelion - far more than a weed" (PDF). Frapez.com. Frapez soothie spa. Retrieved 30 May 2010.
  28. ↑ "Den virtuella floran: Taraxacum F. H. Wigg. - Maskrosor" (in Swedish). Linnaeus.nrm.se. Retrieved 2010-07-03.
  29. ↑ "Sauted Dandelion Greens", ItalianFoodForever.com
  30. ↑ Kleonikos G. Stavridakis; Κλεόνικος Γ. Σταυριδάκης (2006). Wild edible plants of Crete - Η Άγρια βρώσιμη χλωρίδα της Κρήτης. Rethymnon Crete. ISBN 960-631-179-1.
  31. ↑ Castronovo Fusco, MA (2008-04-15). "Dandelion as underrated as underfoot". New Jersey On-Line. Retrieved 2011-03-07.
  32. ↑ "Dandelion greens, raw". Nutritiondata.com. Retrieved 2011-03-07.
  33. 1 2 3 4 Katrin Schütz, Reinhold Carle & Andreas Schieber (2006). "Taraxacum—a review on its phytochemical and pharmacological profile". Journal of Ethnopharmacology. 107 (3): 313–323. doi:10.1016/j.jep.2006.07.021. PMID 16950583.
  34. ↑ D. L. Buckingham & W. J. Peach (2005). "The influence of livestock management on habitat quality for farmland birds". Animal Science. 81: 199–203. doi:10.1079/asc50700199.
  35. ↑ Pellett, Frank Chapman (1920). American Honey Plants; Together With Those Which Are of Special Value to the Beekeeper as Sources of Pollen. American Bee Journal Publication. p. 178. ISBN 1-152-86271-5.
  36. ↑ Anon. "Companion Planting for Vegetables & Plants". Country living and farm lifestyles. countryfarm-lifestyles.com. Retrieved 2011-03-07.
  37. ↑ "Welcome to Main Street White Sulphur Springs...Make it home". Wssmainstreet.org. Retrieved 2010-07-03.
  38. ↑ "Songs of the University of Rochester". Lib.rochester.edu. 2010-01-14. Retrieved 2010-07-03.
  39. ↑ Bill Church (2006). Medicinal Plants, Trees, & Shrubs of Appalachia – A Field Guide. Lulu.com. p. 28. ISBN 978-1-4116-4486-1.
  40. ↑ Lourdes Rodriguez-Fragoso, Jorge Reyes-Esparza, Scott W. Burchiel, Dea Herrera-Ruiz & Eliseo Torres (2008). "Risks and benefits of commonly used herbal medicines in Mexico". Toxicology and Applied Pharmacology. 227 (1): 125–135. doi:10.1016/j.taap.2007.10.005. PMC 2322858Freely accessible. PMID 18037151.
  41. 1 2 Stewart-Wade, S. M.; Newmann, S.; Collins, L. L.; Boland, G. J. (2002). "The biology of Canadian weeds. 117. Taraxacum officinale G.H. Weber ex Wiggers". Canadian Journal of Plant Science. 82: 825–853. doi:10.4141/P01-010.
  42. ↑ Richardson, Jonathan (1985). "In praise of the archenemy". Audubon. 87: 37–39.
  43. ↑ "Making Rubber from Dandelion Juice". sciencedaily.com. sciencedaily.com. Retrieved 22 November 2013.
  44. ↑ "Fraunhofer and Continental come together when the dandelion rubber meets the road". Retrieved 31 May 2014.

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