Simplified schematic of an island's flora - all its plant species, highlighted in boxes.
In botany, flora (plural: floras or florae) has two meanings. The first meaning, flora of an area or of time period, refers to all plant life occurring in an area or time period, especially the naturally occurring or indigenous plant life. The second meaning refers to a book or other work which describes the plantspecies occurring in an area or time period, with the aim of allowing identification. Some classic and modern floras are listed below.
Plants are grouped into floras based on region, period, special environment, or climate. Regions can be geographically distinct habitats like mountain vs. flatland. Floras can mean plant life of an historic era as in fossil flora. Lastly, floras may be subdivided by special environments:
Native flora. The native and indigenous flora of an area.
Agricultural and garden flora. The plants that are deliberately grown by humans.
Weed flora. Traditionally this classification was applied to plants regarded as undesirable, and studied in efforts to control or eradicate them. Today the designation is less often used as a classification of plant life, since it includes three different types of plants: weedy species, invasive species (that may or may not be weedy), and native and introduced non-weedy species that are agriculturally undesirable. Many native plants previously considered weeds have been shown to be beneficial or even necessary to various ecosystems.
Traditionally floras are books, but some are now published on CD-ROM or websites. The area that a flora covers can be either geographically or politically defined. Floras usually require some specialist botanical knowledge to use with any effectiveness.
A flora often contains diagnostic keys. Often these are dichotomous keys, which require the user to repeatedly examine a plant, and decide which one of two alternatives given in the flora best applies to the plant.
Classic floras
Floristic regions in Europe according to Wolfgang Frey and Rainer Lösch
Britton, N. L., and Percy Wilson. Scientific Survey of Porto Rico and the Virgin Islands — Volume V, Part 1: Botany of Porto Rico and the Virgin Islands: Pandanales to Thymeleales. New York: New York Academy of Sciences, 1924.
Nathaniel Lord Britton and Hon. Addison Brown. An Illustrated Flora of the Northern United States and Canada. In three volumes. Dover Publications, 1913, 1970. ISBN 0-486-22642-5
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