General · EdgepediaSeptember 17, 20265 min read

Geranium

Geranium is a genus of about 337 accepted species of annual and perennial herbs in the family Geraniaceae, known commonly as cranesbills for the beak-shaped fruit. The genus was first published by Linnaeus in Species Plantarum in 1753, and its native range spans temper and subtropical regions to tropical mountains worldwide.¹ It is the largest genus in its family, with roughly 350 species, ahead of Pelargonium with about 280.²

Key fact	Detail
Scientific name	Geranium Tourn. ex L., first published in Sp. Pl.: 676 (1753)¹
Species count	337 accepted species per Plants of the World Online; ca. 350 per the Kew family treatment¹^•²
Native range	Temperate and subtropical to tropical mountains, on every continent except Antarctica¹
Fruit	A schizocarp with five 1-seeded, awned mericarps that separate elastically from a central beak, the source of the name cranesbill²
Flowers	Actinomorphic (radially symmetrical), with 5 sepals, 5 petals, and 10 stamens²^•³
Common confusion	The bedding plants sold as "geraniums" are usually Pelargonium, a separate genus since 1789³^•⁴
Seed dispersal	Explosive; in G. maculatum seeds are thrown an average of 3 m and up to 9 m⁵

Description

Geraniums are annual or perennial herbs with stipules and leaves that are pinnately or palmately lobed or compound, arranged alternately or oppositely.² The flowers are usually bisexual and radially symmetrical, with five sepals and five free petals. Fertile stamens number 10 in Geranium, in two whorls, a count that separates the genus from Erodium, which has five.² Leaf venation is usually palmate in Geranium and pinnate in Erodium.²

The fruit is the family's most distinctive structure: a schizocarp with five one-seeded, awned mericarps that separate elastically from a central beak. The elongate styles are hygroscopically active and curl when exposed to water, releasing the seeds; this beaked carpel gives the genus its common name, cranesbill.²^•⁶

Geranium versus Pelargonium

Geranium and Pelargonium were treated as one genus until the late 18th century. The shared feature was the crane's-bill-shaped seed container, from the Greek geranos, crane. The decisive difference is flower symmetry: Geranium species have actinomorphic flowers, while Pelargonium flowers are zygomorphic.³ In 1789 the French botanist Charles L'Héritier de Brutelle separated Pelargonium into its own genus on this basis, along with a nectar tube absent from true geraniums.⁴

The common name nevertheless stayed with the popular garden plant. The bedding and balcony plants most people call geraniums are Pelargonium species, mostly native to southern Africa, and nurseries had established "geranium" as the trade name before the botanical distinction reached gardeners.³^•⁷ Other visible differences follow the split: Pelargonium flowers have two upper petals differing in color and pattern from the three lower ones and two to seven fertile stamens, while Geranium flowers have five equal petals and 10 or more stamens. Pelargonium seeds carry a plumed end that lets them float on the breeze; Geranium seeds lack the plume and are flung from the plant.⁷

Distribution and habitat

The genus is native across temperate and subtropical regions and tropical mountains, from Alaska and Greenland to Tierra del Fuego, and from Iceland to New Zealand; Kew lists native occurrences in well over 200 regions and introduced populations in places such as Sri Lanka, Réunion, and the Falkland Islands.¹ In the Neotropics, Geranium occurs in most major mountains of tropical America and some dry coastal areas, but is absent from lowland tropical forest.² Some species reach oceanic islands as distant as Madeira and Hawaii.⁸

The genus remains taxonomically active. Carlos Aedo's monograph of Geranium (2023, CSIC Madrid, 898 pages) is the current reference work, and new species continue to be described; a 2025 study reported Geranium swatense as new to India and assessed it as endangered or vulnerable.⁹^•¹⁰

Reproduction and seed dispersal

Geranium flowers are visited by insects of many kinds and sizes, which serve as pollinators.¹¹ In the North American woodland herb Geranium maculatum, plants are self-compatible but depend on pollinators for seed set, and young plants usually first bloom in their second or third year.⁵ Experimental work in central Illinois populations tested whether seed production is limited by pollen delivery, comparing supplementarily pollinated flowers with controls receiving natural pollination.¹²

Seed dispersal is explosive. As the dried fruit splits, the mericarps are thrown from the plant; in G. maculatum the measured average dispersal distance is 10 feet (3 m), with a maximum of 30 feet (9 m).⁵ Studies of G. molle suggest the mechanism favors maximizing dispersal distance.¹³

Cultivation

Hardy geraniums are long-lived, easy-to-grow border plants suited to cottage-garden plantings. The Royal Horticultural Society notes that G. 'Orion' and G. clarkei 'Kashmir White' tolerate most soils including heavy clay; G. macrorrhizum, G. nodosum, and G. phaeum do well in dry, shaded spots; and small rock-garden types such as G. dalmaticum and G. cinereum 'Ballerina' want free-draining sites. Two Canary Island natives, G. maderense and G. palmatum, need frost-free winter protection.¹⁴ Cambridge University Botanic Garden holds a national plant collection of Geranium species and primary hybrids, and recent RHS trials have awarded the Award of Garden Merit to top-performing entries.⁸

Medicinal interest

Geranium species have a long record of ethnomedicinal use across many countries, and reviews catalog phytochemical compounds and reported pharmacological activities, presenting the genus as a resource for drug discovery research.¹⁵ G. maculatum was used as a medicinal plant in eighteenth-century North America after its introduction to cultivation.¹⁶ Aromatic oils sold as "geranium oil" come not from this genus but from scented Pelargonium leaves, whose main constituents include citronellol, geraniol, eugenol, and pinene.⁷

References

Topic: Encyclopedia › Life and health › Plants and algae › Seed plants › Other flowering plants › Rosids

Initially written Sep 17, 2026 · Reviewed: Sep 30, 2026; Oct 21, 2026 · Edited: Sep 30, 2026; Oct 21, 2026 · Last review: Oct 21, 2026

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