Dandelions

''Taraxacum'' () is a 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 has a near-cosmopolitan distribution, absent only from tropical and polar areas.POWO
/ref> Two of the most common species worldwide, '' T. officinale'' (the common dandelion) and '' T. erythrospermum'' (the red-seeded dandelion), are European species introduced into North America, where they are non-native. Dandelions thrive in temperate regions and can be found in yards, gardens, sides of roads, among crops, and in many other habitats.

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.

Etymology

The Latin name ''Taraxacum'' derives from the Arabic , meaning "bitter herb".Gledhill, David (2008). ''The Names of Plants''. Cambridge University Press. (hardback), (paperback). pp 279, 371 The Arabic term is possibly of Persian origin. Persian polymath Al-Razi used the word in relation to dandelions, chicory, and endives. Al-Razi wrote "the is like chicory, but more efficacious"; it is unclear exactly to which plant Al-Razi referred however. If Persian in origin, the word could have originally meant "bitter purslane" from (, 'bitter') and (, 'purslane'). Gerard of Cremona, in translating Arabic to Latin around 1170, spelled it ''tarasacon''.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 طرشقون‎ ''tarashaqun'' is derivable in turn from Persian تلخ چکوک ''talkh chakok'', bitter herb
Downloadable at Archive.org
.

The English name, dandelion, is a borrowing of the French 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 the equivalent French ') refers to the strong diuretic effect of the plant's leaves. In Swedish, it is called (worm rose) after the thrip nymphs usually present on the plant.

Description

''Taraxacum'' species 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. A number of ''Taraxacum'' species can act as ruderals, species that rapidly colonise disturbed soil. The common dandelion (''T. officinale'') has been introduced over much of the temperate world, and it is especially effective at spreading along roads, cemeteries, lawns, and pastures. A week or two after flowering, the dandelion's flower becomes a round seed head. The bracts, specalized leaves around the flower, curve backwards. The parachute ball fully opens into a sphere, and the yellow petals fall away. When development is complete, the mature seeds are attached to white, fluffy "parachutes" which easily detach from the seedhead and glide by wind, dispersing.

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 attatched to a hollow stem ( scape) that is usually leafless and rises or more above the ground. 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'' containing many single-seeded fruits called cypselae, similar to achenes. Each cypsela is attached to a pappus of fine hair-like material which enables anemochorous (wind-aided) dispersal over long distances.

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 maximise dispersal and germination.In ''Taraxacum'' ovules, the megaspore mother cell is the only cell committed to enter the meiotic process.Cornaro L, Banfi C, Cavalleri A, van Dijk PJ, Radoeva T, Cucinotta M, Colombo L. Apomixis at high resolution: unravelling diplospory in Asteraceae. J Exp Bot. 2025 Apr 9;76(6):1644-1657. doi: 10.1093/jxb/erae477. PMID 39673465; PMCID: PMC11981899. ''T. officinale'' is able to reproduce by a sexual meiotic process involving the production of haploid gametes, as well as by an asexual parthenogenetic meiotic process, referred to as apomixis, that produces diploid seeds genetically identical to the mother plant. Parthenogenesis permits the autonomous development of an unreduced egg cell into an embryo without the requirement of fertilisation.''Taraxacum'' flowers contain various 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 fibre inulin. Dandelion greens contain lutein