Geranium is a large genus of approximately 400–570 species of annual, biennial, and perennial flowering plants in the family Geraniaceae, commonly known as cranesbills. Plants range in height from around 20 cm to 1.2 m and are found throughout temperate regions worldwide, with their greatest diversity concentrated in the eastern Mediterranean region. They also occur in tropical mountain areas on multiple continents.
The leaves are palmately lobed or divided, with narrow, pointed segments typically arranged in a broadly circular outline. Flowers are five-petalled and appear in shades of white, pink, purple, or blue, often with distinctive darker veining. The fruit is the defining feature of the genus: five seed-bearing cells are joined to a central elongated column. When ripe, the cells separate explosively and each flings a single seed away from the parent plant, an efficient dispersal mechanism that gives rise to the common name "cranesbill" — the unripe column resembling a crane's head and beak.
The genus was formally described by Carl Linnaeus in his landmark work Species Plantarum (1753), cited as Geranium Tourn. ex L. The GBIF database records 568 descendant taxa under this genus. Several genera have been placed in synonymy with Geranium over time, including Geranion, Geraniopsis, Neurophyllodes, Robertiella, and Robertium.
Geraniums are highly valued garden plants, tolerating a wide range of soils from light sandy to heavy clay, and growing in conditions from full sun to part shade. They are notably resistant to browsing by deer and rabbits. Some species show unusual biological traits: Geranium viscosissimum (sticky geranium) is protocarnivorous, and several species exhibit gynodioecy, maintaining both female and hermaphrodite plants within populations.
Etymology
The genus name Geranium comes from the Ancient Greek word géranos, meaning "crane." The reference is to the elongated central column of the fruit, which resembles the head and beak of a crane. This gives rise to the widely used common name "cranesbill." The fruit itself consists of five seed-bearing cells joined at the base of this column; when mature, each cell springs away from the column, dispersing its seed. The name was used by Linnaeus in the genus-level treatment published in Species Plantarum in 1753.
Distribution
The genus has a nearly worldwide distribution in temperate climates, including Europe, Asia, the Americas, Africa, and Australasia, with the eastern Mediterranean recognized as the centre of greatest diversity. Species also occur in montane tropical zones. In Switzerland alone, Info Flora documents 24 species and subspecies, including G. pratense, G. sanguineum, G. sylvaticum, G. columbinum, G. argenteum, and G. bohemicum. In North America, G. maculatum is native to eastern forests and G. bicknellii to boreal and northern regions.
Taxonomy
Geranium Tourn. ex L. is placed in family Geraniaceae, order Geraniales, class Magnoliopsida, phylum Tracheophyta, kingdom Plantae. The genus was established in Linnaeus's Species Plantarum: 676 (1753). GBIF records 568 descendant taxa under usageKey 2889949.
Five genera have been treated as synonyms: Geranion St.-Lag. (1880), Geraniopsis Chrtek (1968), Neurophyllodes (A.Gray) O.Deg. (1937) — originally applied to Hawaiian cranesbill taxa, Robertiella Hanks (1907), and Robertium Picard (1837). The Info Flora Swiss checklist assigns the genus the ID 1021299.
It is important to note that the name "geranium" is also applied in horticulture and common usage to the genus Pelargonium, which is a distinct genus in the same family; true Geranium species differ from pelargoniums in having actinomorphic (radially symmetrical) flowers.
Ecology
Geranium species support a range of invertebrate communities. Larvae of several Lepidoptera species — including brown-tail moth, ghost moth, and mouse moth — feed on the foliage. The explosive seed dispersal mechanism of the carpels is an adaptation for directed seed ejection rather than reliance on wind or animal vectors.
Some species exhibit gynodioecy, a reproductive system in which populations contain both female plants and hermaphrodites. Geranium viscosissimum (sticky geranium) has sticky glandular hairs on its stems and leaves that trap small insects, placing it in the category of protocarnivorous plants, though it lacks confirmed digestive enzymes.
No Geranium species are currently listed in the IUCN Global Invasive Species Database as problematic invasives.
Cultivation
Geraniums are adaptable garden plants that thrive in moderately fertile, moisture-retentive, well-draining soil. They tolerate a wide range of soil textures, from light sandy to heavy clay, and a broad pH range from acidic to basic. They grow well in positions from full sun to part shade. A practical advantage for gardeners is that members of the genus are rarely troubled by deer or rabbit browsing.
Numerous cultivars have received the Royal Horticultural Society Award of Garden Merit, including 'Rozanne', 'Johnson's Blue', 'Ann Folkard', and 'Wargrave Pink'. The genus includes over 20 commonly cultivated species.
Propagation
Geraniums can be propagated by three main methods: seed, division, and cuttings. Seed can be sown in spring or autumn in a cold frame; once seedlings are large enough to handle they are pricked into individual pots and grown on before planting outdoors in summer. Division of established clumps is carried out in autumn or spring. Semiripe cuttings can be taken in summer.
Cultural & Traditional Uses
In folk medicine, the whole plant — especially the roots — has been used for its astringent and styptic properties, including as a remedy for sore throats. The leaves are edible raw or cooked, and the flowers are edible raw, though neither is considered a choice food source. These uses are documented across multiple cranesbill species rather than being specific to a single one.
