Pelargonium occurs in a large number of growth forms, including herbaceous annuals, shrubs, subshrubs, stem succulents and geophytes.

The Geraniaceae have a number of genetic features unique amongst angiosperms, including highly rearranged plastid genomes differing in gene content, order and expansion of the inverted repeat.

[11][12] Dillenius, who referred to these seven species with apparent unique characteristics as Geranium Africanum (African Geranium)[13] suggested "Possent ergo ii, quibus novi generis cupido est, ea, quorum flores inaequales vel et irrregulares sunt, Pelargonia vocare" (Those who wish a new genus can therefore call those, whose flowers are unequal or irregular, ‘Pelargonia’).

[12] The eventual distinction between them was made by Charles L’Héritier based on the number of stamens or anthers, seven in the case of Pelargonium.

[16][11] Pelargonium is distinguished from the other genera in the family Geraniaceae by the presence of a hypanthium, which consists of an adnate nectar spur with one nectary, as well as a generally zygomorphic floral symmetry.

These are as follows; All subdivision classifications had depended primarily on morphological differences till the era of phylogenetic analyses (Price and Palmer 1993).

As before the internal structure of the clades supported monophyly of some sections (Myrrhidium, Chorisma, Reniformia, Pelargonium, Ligularia and Hoarea) but paraphyly in others (Jenkinsonia, Ciconium, Peristera).

[22][14] Pelargonium is a large genus within the family Geraniaceae, which has a worldwide distribution in temperate to subtropical zones with some 800 mostly herbaceous species.

The diurnal butterflies Cacyreus marshalli and C. tespis (Lycaenidae), native to southern Africa, also feed on Geranium and Pelargonium.

[24] The Japanese beetle, an important agricultural insect pest, becomes rapidly paralyzed after consuming flower petals of the garden hybrids known as "zonal geraniums" (P. × hortorum).

[25][26][27][28] Research conducted by Dr. Christopher Ranger with the USDA Agricultural Research Service and other collaborating scientists have demonstrated the excitatory amino acid called quisqualic acid present within the flower petals is responsible for causing paralysis of the Japanese beetle.

[31] A study by the Laboratory of Apiculture & Social Insects group at the University of Sussex on the attractiveness of common garden plants to pollinators found that a cultivar of Pelargonium × hortorum was unattractive to pollinators in comparison to other selected garden plants such as Lavandula (lavender) and Origanum.

Geranium bronze are currently listed as an A2 quarantine pest by the European and Mediterranean Plant Protection Organization and can cause significant damage to Pelargonium species.

[33] Various types of Pelargonium are regular participants in flower shows and competitive events, with numerous societies devoted exclusively to their cultivation.

In 1631, the English gardener John Tradescant the elder bought seeds from Rene Morin in Paris and introduced the plant to England.

[16] There was little attempt at any rational grouping of Pelargonium cultivars, the growing of which was revived in the mid-twentieth century, and the origins of many if not most were lost in obscurity.

Those pelargoniums which were largely derived from P. zonale he referred to as P. × hortorum (i.e. from the garden), while those from P. cucullatum he named P. × domesticum (i.e. from the home).

These include;[49] These may then be combined to form the code, e.g. Pelargonium 'Chelsea Gem' (Z/d/v), indicating Zonal Double with variegated foliage.

[36][47] Zonal pelargoniums are mostly bush-type plants with succulent stems grown for the beauty of their flowers, traditionally red, salmon, violet, white or pink.

[56] Fancy-leaf zonal pelargoniums – besides having green leaves with or without zoning, this group also have variable coloured foliage[50] that is sometimes used in classifying for exhibition purposes, e.g. ‘Bicolour’, ‘Tricolour’, ‘Bronze’ or ‘Gold’.

[50]Usually of lax growth (trailing), mainly due to the long thin stems, with thick, waxy ivy-shaped stiff fleshy evergreen leaves developed by the species P. peltatum to retain moisture during periods of drought.

Ivy-leaved pelargoniums embrace all such growth size types including small-leaved varieties and genetic hybrid crosses, which display little or no zonal characteristics.

They have rounded, sometimes lobed or partially toothed (serrated) leaves, unlike the Zonal groups, without any type of zoning.

The majority of Angel cultivars originate from a cross between P. crispum and a Regal variety in the early part of the 20th century.

Angels have grown in popularity in the last 30 years or so due mainly to an explosion of new varieties being released by specialist nurseries resulting from the work done by dedicated amateur hybridisers.

These hybrisers have managed to obtain many new flower colour breaks and tighter growth habits resulting in plants suitable for all sorts of situations.

Shrubby evergreen perennials grown chiefly for their fragrance, may be species or cultivars but all must have a clear and distinct scented foliage.

Species pelargoniums have a large diversity of characteristics in habit, shape, size and colour, which probably accounts for them having retained their popularity for more than 300 years.

Geranium (Pelargonium) oil is considered a relaxant in aromatherapy, and in recent years, respiratory/cold remedies made from P. sidoides and P. reniforme have been sold in Europe and the United States.

[citation needed] It is used internally for debility, gastroenteritis, and hemorrhage and externally for skin complaints, injuries, and neuralgia and throat infections.