T.E.R:R.A.I.N - Taranaki Educational Resource: Research, Analysis and Information Network

Taraxacum officinale (Dandelion)

Kingdom: Plantae 
Division: Magnoliophyta 
Class: Magnoliopsida 
Order: Asterales 
Family: Asteraceae 
Genus: Taraxacum
Scientific name: Taraxacum officinale
Common name: Dandelion

Dandelion is a widely distributed perennial broadleaf weed found throughout the world and in New Zealand. It consists of a complex of biotypes that vary with environmental conditions. It inhabits perennial crop fields, disturbed sites, lawns, orchards, vineyards, and nurseries crops. It is a host of aster yellow disease, which affects a number of vegetable crops. Because dandelion contains high amounts of certain minerals, it serves as a complement to pasture forage for livestock.
Dandelions flower nearly year-round in mild climates. The bright yellow flower head is 2–3.5 cm across and is found singly on the tip of a hollow, leafless stalk that is 7.5–30 cm tall. The flower head consists of many, small, yellow, petal-like flowers (ray flowers).
The seeds are tiny, brown achene, about 3 mm) in length and are attached to a long, slender stalks, terminating in a parachute-like structure (pappus) consisting of hairs. Collectively the seeds form a fuzzy, grey-white, spherical fruiting head (dandelion clock). The seeds are transported by wind. Dandelions reproduce by seeds that can germinate almost year-round and also by their taproots which can also send up new shoots.
The medicinal and nutritional uses for the dandelion are the main reasons why there are so many dandelions today. Dandelions have been purposely cultivated and widely used throughout history. 

For more details on its medical use visit  http://en.wikipedia.org/wiki/Medicinal_properties_of_dandelion  

A lawn infested with Taraxacum officinale (Dandelion)

A fast-growing dandelion in a lawn

Flower bud

Seed head forming.

A white seed head of a dandelion

A mature seed head called a "Dandelion clock".

The seeds with pappus that carries them on the wind.

Thanks to Wikipedia for text and information     https://creativecommons.org/licenses/by-sa/3.0/