Escaping in memory from the season’s harsh, chill winds, I cast my mind back to the dandelion days of last spring, summer and early autumn. From March until October the vivid, cadmium yellow flowers of Taraxacum officinale, or common dandelion – and their superceding, globular silver seed-heads – are found to be distributed widely and in abundance across the gently dipping shoulders of the Don river valley.
We have thus observed the dandelion – that most cosmopolitan of weeds – on many patches of wasteland and also, in naughty proliferation, across the cultivated lawns and pastures of Netherthorpe, Upperthorpe, Shalesmoor, Neepsend and Wardsend.
The dandelion is such a common plant that it is all to easy to become blind to its two extraordinarily complex stages of fruit and flower … but it is equal in its mystery to any other of the botanical organisms that we have encountered on our journeys around these parts. Not least, it would appear to confound the efforts of taxonomists to define its species with any precision – which is perhaps no surprise when one gives due consideration to this humble plant’s very singular ability to propagate in such numbers and to spread it’s progeny so widely and with such abandon through the action of the wind.
Taraxacum officinale, the common dandelion (often simply called “dandelion”), is a herbaceous perennial plant of the family Asteraceae (Compositae). It can be found growing in temperate regions of the world, in lawns, on roadsides, on disturbed banks, on the shores of water ways, and other areas with moist soils. Taraxacum officinale is considered a weed species, especially in lawns and along roadsides; but it is sometimes used as a medicinal and in food preparation. As a nearly cosmopolitan weed, the common dandelion is best known for its bright yellow flower heads that turn into round balls of silver tufted fruits that blow away on the wind.
The dandelion grows from generally unbranched taproots and produces one to more than ten stems that are typically 5 to 40 cm tall but sometimes up to 70 cm tall. The stems can be tinted purplish, are upright or lax, and produce flower heads that are held as tall or taller than the foliage. The foliage is upright growing or horizontally orientated, with leaves that are unwinged or having narrowly winged petioles. The stems can be glabrous or are sparsely covered with short hairs. The 5–45 cm long and 1–10 cm wide leaves are oblanceolate, oblong, or obovate in shape with the bases gradually narrowing to the petiole The leaf margins are typically shallowly lobed to deeply lobed and often lacerate or toothed with sharp or dull teeth and the leaves are all basal; each flowering stem lacks bracts and has one single flower head.
The yellow flower heads lack receptacle bracts and all the flowers, which are called florets, are ligulate and bisexual. The calyculi (the cup like bracts that hold the florets) are composed of 12 to 18 segments: each segment is reflexed and sometimes glaucous. The lanceolate shaped bractlets are in 2 series with the apices acuminate in shape. The 14 to 25 mm wide involucres are green to dark green or brownish green with the tips dark gray or purplish. The florets number 40 to over 100 per head, having corollas that are yellow or orange-yellow in color. The fruits, which are called cypselae, range in color from olive-green or olive-brown to straw-colored to grayish, they are oblanceoloid in shape and 2 to 3 mm long with slender beaks. The fruits have 4 to 12 ribs that have sharp edges. The fruits are mostly produced by apomixis (a form of asexual reproduction through the seeds). It blooms from March until October.
The silky pappi, which form the parachutes, are white to silver-white in color and around 6 mm wide. Dandelion plants have milky sap that has been used as a mosquito repellent; the milk has also been used to treat warts, as a folk remedy.
Taraxacum officinale is a common colonizer after fires, both from wind blown seeds and seed germination from the seed bank. The seeds remain viable in the seed bank for many years, with one study showing germination after nine years. This species is a somewhat prolific seed producer, with 54 to 172 seeds produced per head, and a single plant can produce more than 5,000 seeds a year. It is estimated that more than 97,000,000 seeds/hectare could be produced yearly by a dense stand of dandelions. When released, the seeds can be spread by the wind up to several hundred meters from their source, the seeds are also a common contaminate in crop and forage seeds.
The dandelion has historically had many English common names including: blowball, lion’s-tooth, cankerwort, milk-witch, yellow-gowan, Irish daisy, monks-head, priest’s-crown and puff-ball; other common names include: faceclock, pee-a-bed, wet-a-bed, canker-wort, and swine’s snout
Carl Linnaeus named the species Leondonton Taraxacum in 1753. The genus name Taraxacum, might be from the Arabic word “Tharakhchakon“,or from the Greek “Tarraxos“. The common name “dandelion,” comes from the French phrase “dent de lion” which means “lion’s tooth”, in reference to the jagged shaped foliage. The taxonomy of the genus Taraxacum is complicated by apomictic and polyploid lineages, and the taxonomy and nomenclatural situation of Taraxacum officinale is not yet fully resolved. This situation has been further complicated in the past by the recognition of numerous species, subspecies and microspecies. E.g. Rothmaler’s flora of Germany recognizes roughly 70 microspecies.
While the dandelion is considered a weed by most gardeners and lawn owners, the plant has several culinary uses. The specific name officinalis refers to its value as a medicinal herb, and is derived from the word opificina, later officina, meaning a workshop or pharmacy. Dandelion flowers can be used to make dandelion wine; and it has also been used in a saison ale called Pissenlit (literally “wet the bed” in French) which is made in Belgium. The greens are used in salads, the roots have been used to make a coffee-like drink and the plant was used by Native Americans as a food and medicine. Ground roasted dandelion root can be used as a coffee substitute. In Silesia, and other parts of Poland, dandelion flowers are used to make a honey substitute, to which lemon is added (so-called May-honey). This “honey” is believed to have a medicinal value, in particular against liver problems.
Dandelion root is a registered drug in Canada, sold principally as a diuretic. A leaf decoction can be drunk to “purify the blood”, for the treatment of anemia, jaundice, and also for nervousness. A hepatoprotective effect of chemicals extracted from dandelion root has been reported. Drunk before meals, dandelion root coffee is claimed to stimulate digestive functions and function as a liver tonic.
Paul Evans, 22 January 2012