Dandelion Blackwell 0136

''Taraxacum'' () is a large genus of flowering plants in the family Asteraceae, which consists of species commonly known as dandelions. The scientific and hobby study of the genus is known as taraxacology. The genus is native to Eurasia and North America, but the two most commonplace species worldwide, '' T. officinale'' (the common dandelion) and '' T. erythrospermum'' (the red-seeded dandelion), were introduced from Europe into North America, where they now propagate as wildflowers. Both species are edible in their entirety. The common name ''dandelion'' ( , from French , meaning 'lion's tooth') is also given to specific members of the genus.

Like other members of the family Asteraceae, they have very small flowers collected together into a composite flower head. Each single flower in a head is called a ''floret''. In part due to their abundance, along with being a generalist species, dandelions are one of the most vital early spring nectar sources for a wide host of pollinators. 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.

In general, the leaves are long or longer, simple, lobed-to-pinnatisect, 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 or more 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 in diameter and consist entirely of ray florets. The flower heads mature into spherical seed heads sometimes called blowballs or clocks (in both British and American English) containing many single-seeded fruits called achenes. Each achene is attached to a pappus of fine hair-like material which enables 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''. 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.

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 (i.e. morphologically distinct clonal populations) are recognised in nine loosely defined sections, of which 40 are "probably endemic". 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. When development is complete, the mature seeds are attached to white, fluffy "parachutes" which easily detach from the seedhead and glide by wind, dispersing.

The seeds are able to cover large distances when dispersed due to the unique morphology of the pappus which works to create a unique type of vortex ring that stays attached to the seed rather than being sent downstream. In addition to the creation of this vortex ring, the pappus can adjust its morphology depending on the moisture in the air. This allows the plume of seeds to close up and reduce the chance to separate from the stem, waiting for optimal conditions that will maximize dispersal and germination.

Similar plants

Many similar plants in the family Asteraceae with yellow flowers are sometimes known as false dandelions. Dandelion flowers are very similar to those of cat's ears (''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 cat's ear 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 cat's ears 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.

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 due to the presence of apomixis: any morphologically distinct clonal population would deserve its own microspecies. Phylogenetic approaches are also complicated by the accelerated mutation in apomixic lines and repeated ancient hybridization events in the genus.

As of 1970, the group is divided into about 34 macrospecies or sections, and about 2000 microspecies; some botanists take a much narrower view and only accept a total of about 60 (macro)species. By 2015, the number has been revised to include 60 sections and about 2800 microspecies. 30 of these sections are known to reproduce sexually.

About 235 apomictic and polyploid microspecies have been recorded in Great Britain and Ireland alone.

Selected species

* '' Taraxacum albidum'', the white-flowered Japanese dandelion, a hybrid between ''T. coreanum'' and ''T. japonicum''
* ''Taraxacum aphrogenes'', the Paphos dandelion
* '' Taraxacum arcticum''
* '' Taraxacum balticum''
* '' Taraxacum brachyceras''
* ''Taraxacum brevicorniculatum'', frequently misidentified as ''T. kok-saghyz'' and a poor rubber producer
* '' Taraxacum californicum'', the California dandelion, an endangered species
* '' Taraxacum centrasiaticum'', the Xinjiang dandelion
* '' Taraxacum ceratophorum'', the horned dandelion, considered by some sources to be a North American subspecies of ''T. officinale'' (''T. officinale'' subsp. ''ceratophorum'')
* '' Taraxacum coreanum''
* '' Taraxacum desertorum''
* ''Taraxacum erythrospermum'', the red-seeded dandelion, often considered a variety of ''T. laevigatum'' (i.e., ''T. laevigatum'' var. ''erythrospermum'')
* '' Taraxacum farinosum'', the Turkish dandelion
* '' Taraxacum holmboei'', the Troödos dandelion
* ''Taraxacum hybernum''
* ''Taraxacum japonicum'', the Japanese dandelion, no ring of smallish, downward-turned leaves under the flower head
* ''Taraxacum kok-saghyz'', the Kazakh dandelion, which produces rubber
* ''Taraxacum laevigatum'', the rock dandelion, achenes reddish brown and leaves deeply cut throughout the length, inner bracts' tips are hooded
* ''Taraxacum lissocarpum''
* '' Taraxacum minimum''
* '' Taraxacum mirabile''
* ''Taraxacum officinale'' (syn. ''T. officinale'' subsp. ''vulgare''), the common dandelion, found in many forms
* '' Taraxacum pankhurstianum'', the St. Kilda dandelion
* '' Taraxacum platycarpum'', the Korean dandelion
* '' Taraxacum pseudoroseum''
* '' Taraxacum suecicum''

Cultivars

*'Amélioré à Coeur Plein' yields an abundant crop without taking up much ground, and tends to blanch itself naturally, due to its clumping growth habit.
*'Broad-leaved' - The leaves are thick and tender and easily blanched. In rich soils, they can be up to 60 cm (2') wide. Plants do not go to seed as quickly as French types.
*'Vert de Montmagny' is a large-leaved, vigorous grower, which matures early.

History

Dandelions are thought to have evolved about 30 million years ago in Eurasia. Fossil seeds of ''Taraxacum tanaiticum'' have been recorded from the Pliocene. Dandelions have been used by humans for food and as an herb for much of recorded history. They were well known to ancient Egyptians, Greeks and Romans, and are recorded to have been used in traditional Chinese medicine for over a thousand years. The plant was used as food and medicine by Native Americans. Dandelions were probably brought to North America on the ''Mayflower'' for their supposed medicinal benefits.

Etymology

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

The English name, dandelion, is a corruption of the French ''dent de lion'' 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; other common names include ''faceclock'', ''pee-a-bed'', ''wet-a-bed'',
''swine's snout'', white endive, and wild endive.

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

In Swedish, it is called ''maskros'' (worm rose) after the small insects (thrips) usually present in the flowers. 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 latex that is produced when the stems are cut. The Danish name ''mælkebøtte'' (sometimes ''fandens mælkebøtte'') means "milk bin" ("the devils milk bin") and also refers to the milky latex (and its ability to spread). Similarly, it is called ''maslačak'' in Croatian, the name coming from the word ''maslac'' or ''maslo'' (butter and clarified butter, respectively). The Welsh (''dant-y-llew''), German (''Löwenzahn''), Norwegian (''løvetann''), Portuguese (''dente de leão'') and Spanish (''diente de león'') names mean the same as the French and the English names. In Czech it is known as ''pampeliška'' where the "liška" part directly translates to a "fox", possibly due to the colour of the flower. In Irish it is ''caisearbhán'', deriving from "curly-haired" and "oats". In Japanese it is タンポポ (pronounced "Tampopo").

Nutrition

Raw dandelion greens contain high amounts of vitamins A, C, and K, and are moderate sources of calcium, potassium, iron, and manganese. Raw dandelion greens are 86% water, 9% carbohydrates, 3% protein, and 1% fat. A 100 gram (oz) reference amount supplies 45 Calories.

Phytochemicals

The raw flowers contain diverse phytochemicals, including polyphenols, such as flavonoids apigenin, isoquercitrin (a quercetin-like compound), and caffeic acid, as well as terpenoids, triterpenes, and sesquiterpenes. The roots contain a substantial amount of the prebiotic fiber inulin. Dandelion greens contain lutein