Pelargonium () is a genus of flowering plants commonly called geraniums, pelargoniums, or storksbills. It includes about 280 species of perennials, succulents, and shrubs. Taxonomist Carl Linnaeus originally included all the species of Pelargonium and Geranium under the latter name. In 1789, Charles Louis L'Héritier de Brutelle separated them into two genera.
While Geranium species are mostly temperate herbaceous plants, dying down in winter, Pelargonium species are evergreen perennials indigenous to warm temperate and tropical regions of the world, with many species in southern Africa. They are drought and heat tolerant but can tolerate only minor frosts. Some species are extremely popular garden plants, grown as houseplants and bedding plants in temperate regions. They have a long flowering period, with flowers mostly in red, orange, or white, but intensive breeding has produced a huge array of cultivars with great variety in size, flower colour, leaf form and aromatic foliage.
Description
thumb|Pelargonium sp., probably a hybrid
thumb|Pelargonium flower
Pelargonium occurs in a large number of growth forms, including herbaceous annuals, shrubs, subshrubs, stem succulents and geophytes. The erect stems bear five-petaled flowers in umbel-like clusters, which are occasionally branched. Because not all flowers appear simultaneously, but open from the centre outwards, this is a form of inflorescence is referred to as pseudoumbels.
The flower has a single symmetry plane (zygomorphic), which distinguishes it from the Geranium flower, which has radial symmetry (actinomorphic). Thus the lower three (anterior) petals are differentiated from the upper two (posterior) petals. The posterior sepal is fused with the pedicel to form a hypanthium (nectary tube). The nectary tube varies from only a few millimeters, up to several centimeters, and is an important floral characteristic in morphological classification. Stamens vary from 2 to 7, and their number, position relative to staminodes, and curvature are used to identify individual species. There are five stigmata in the style.
Taxonomy
thumb|upright|[[Dillenius' introduction of the term 'Pelargonium' in Hortus Elthamensis 1732]]
thumb|upright|[[Pelargonium inquinans, (Geranium Afric. arborescens), Hortus Elthamensis]]
Pelargonium is the second largest genus (after Geranium) within the family Geraniaceae, within which it is sister to the remaining genera of the family in its strict sense,