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From its thick tap root, dark brown, almost black on the outside though white and milky within, the long jagged leaves rise directly, radiating from it to form a rosette Iying close upon the ground, each leaf being grooved and constructed so that all the rain falling on it is conducted straight to the centre of the rosette and thus to the root which is, therefore, always kept well watered. The maximum amount of water is in this manner directed towards the proper region for utilization by the root, which but for this arrangement would not obtain sufficient moisture, the leaves being spread too close to the ground for the water to penetrate. The leaves are shiny and without hairs, the margin of each leaf cut into great jagged teeth, either upright or pointing somewhat backwards, and these teeth are themselves cut here and there into lesser teeth. It is this somewhat fanciful resemblance to the canine teeth of a lion that (it is generally assumed) gives the plant its most familiar name of Dandelion, which is a corruption of the French Dent de Lion, an equivalent of this name being found not only in its former specific Latin name Dens leonis and in the Greek name for the genus to which Linnaeus assigned it, Leontodon, but also in nearly all the languages of Europe.

Two species of dandelion are common lawn weeds, Taraxacum officinale and T. erythrospermum. The two species can be difficult to distinguish. The best distinction between them is the color of the achenes (an achene is a indehiscent, single seeded fruit; in dandelions, the achene bears a fluffy "parachute" that provides for wind dissemination). The achenes of T. erythrospermum are reddish brown, those of T. officinale are olive green.

Here's a web link of interest: http://www.missouriplants.com/Yellowalt/Taraxacum_erythrospermum_page.h tml

Common dandelion is an introduced plant in North America. (Taraxacum officinale, Weber, T. Densleonis, Desf; Leontodon taraxacum, Linn.), though not occurring in the Southern Hemisphere, is at home in all parts of the north temperate zone, in pastures, meadows and on waste ground, and is so plentiful that farmers everywhere find it a troublesome weed, for though its flowers are more conspicuous in the earlier months of the summer, it may be found in bloom, and consequently also prolifically dispersing its seeds, almost throughout the year.

Seed germination occurs at or very near the soil surface. Light increases germination. The seed germinates when soil is moist and soil temperature is at least 50°F; however, germination is more rapid when the soil temperatures are closer to 77°F. Germination occurs throughout the growing season. The seedling stage can last 8 to 15 weeks, depending on temperature and growing conditions. Seedling growth is slower in cold weather. Flowering begins soon after the seedling stage and continues throughout the life of the plant. Dandelion plants can survive for many years, developing massive, thickened crowns 6 to 10 inches across. These perennial plants are well adapted to irrigated areas such as in turfgrass, pastures, or alfalfa where frequent mowing or grazing is practiced.

Dandelions were originally widely distributed throughout northern Eurasia. They have been introduced to North America and Australia as weeds, and perhaps because of their many uses. They are now common plants throughout the temperate regions. The name dandelion is a derivation of the Old French, dent-de-lion, literally "lion's tooth" on account of the sharply lobed leaves of the plant.