Dandelion
Dandelion (Taraxacum officinale) is an extremely common plant through temperate North America and Europe. Its common name, dandelion, comes from the French ‘dent de lion’ (tooth of a lion) referring to the shape of the leaves. It is widely recognized as a weed, a word that generally means that it is an undesirable plant (more details in Chapter 29), undesirable because it grows in places where people are trying to grow something else (e.g. in lawns or in crop fields), and, at least to some people, undesirable because of its looks — perhaps not so much the bright yellow flowers, but more likely because of the fruit heads and the rosettes of leaves in an otherwise uniform carpet of grass. In an ecological sense dandelions are weeds because of their ability to disperse and their association with ‘disturbed’ habitats. In order to persist in a habitat that continually gets disturbed, a plant needs to be ‘tough’: able to survive, grow and reproduce even when disturbances that might kill other plants occur. Weeds typically disperse readily, grow quickly and are able to reproduce in spite of a variety of adversities. At the same time, most ecological weeds are poor competitors and, if disturbances do not occur, weeds will be replaced by species that are better competitors. Consider the distribution of dandelions in the Adirondack Park: they are rarely found in ‘undisturbed’ situations but are found where human activity ‘disturbs’ the area — next to campsites and along the margins of trails, places where competitors of dandelions aren’t able to become established because of the trampling by people. In a comparable situation, dandelion can thrive in agricultural fields because it can tolerate the (often) annual tilling the soil because of the ability of roots to regenerate whole plants.
Phylogeny and taxonomy
Dandelion is an angiosperm, the group whose members produce flowers and seeds (Kingdom Planta, Phylum Magnoliophyta or Anthophyta). Dandelions are in one of the largest families within the angiosperms, the aster / sunflower family (Asteraceae), a group that is usually easy to recognize because the flowers occur in dense clusters (inflorescences) that themselves look like a single flower. The genus Taraxacum is a large and complex group, owing to the complications of apomixis and polyploidy (see discussion below).
Structure
Dandelion has a typical plant structure: a root-shoot axis with leaves produced on the shoot. It is an herbaceous perennial plant that forms rosettes, very short stems with leaves occurring in a circular pattern. As is true in all flowering plants, in the axils of each leaf is an axillary bud. In many plants these axillary buds develop into branches but in dandelion these branch shoots only develop into inflorescences, which, after developing fruits will fall off the plant. Dandelion produces an enlarged storage root (little material can be stored in the very short stem). This root is very capable of producing adventitious