Pelargonium

Pelargonium is a genus of flowering plants that includes about 200 species of perennial, succulent, and shrub plants, commonly known as geraniums. Confusingly, Geranium is also the name of the separate genus that contains the related Cranesbills. Both genera are in the family Geraniaceae. Linnaeus originally included all the species in one genus Geranium, but they were later separated into two genera by Charles L’Héritier in 1789. Gardeners sometimes refer to the members of genus Pelargonium as "pelargoniums" in order to avoid the confusion, but the older common name is still in regular use.

Most species of geranium (Pelargonium) are subtropical or tropical and do not tolerate more than very light frosts. Geraniums are extremely popular garden plants, and hundreds of cultivars have been developed from about 20 of the species.

Geranium leaves are usually alternate, and palmately lobed or pinnate, often on long stacks, and sometimes with light or dark patterns. The erect stems bear five-petaled flowers in umbel-like clusters called pseudoumbels. The shapes of the flowers have been bred to a variety ranging star-shaped to funnel-shaped, and colors include white, pink, red, orange-red, fuchsia and an almost black variety which is quite rare.

Horticultural pelargoniums fall into six major groups, with zonals subdivided further:

• Angel
• Ivy-leaved
• Regal or Martha Washington
• Shrubby-leaved
• Unique
• Zonal – erect and bushy
  • Cactus-flowered
  • Double-flowered
  • Fancy-leaved
  • Formosum hybrid
  • Rosebud
  • Single-flowered
  • Stellar

The first species of Pelargonium known to be cultivated was Pelargonium triste, a native of South Africa. It was probably brought to the botanical garden in Leiden before 1600 on ships that stopped at the Cape of Good Hope. In 1631, the English gardener John Tradescant bought seeds from Rene Morin in Paris and introduced the plant to England. The name Pelargonium was introduced by Johannes Burman in 1738.

References

• Maria Lis-Balchin, ed., Geranium and Pelargonium: History of Nomenclature, Usage and Cultivation. (Taylor and Francis, 2002) ISBN 0415284872