Geranium purpureum

Geranium purpureum
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Eudicots
Clade:	Rosids
Order:	Geraniales
Family:	Geraniaceae
Genus:	Geranium
Species:	G. purpureum
Binomial name
Geranium purpureum Vill.
Synonyms
Homotypic synonyms Geranium robertianum var. purpureum Geranium robertianum proles purpureum (Vill.) Rouy (Vill.) Nyman (Vill.) DC. Robertium purpureum Geranium robertianum purpureum (Vill.) Fourr. Geranium robertianum subsp. purpureum (Vill.) Pers. (Vill.) Picard Robertium vulgare var. purpureum Heterotypic synonyms Geranium robertianum subvar. mediterraneum Hausskn. & Sint. ex R.Knuth Jord. (Jord.) Litard. Geranium robertianum var. mediterraneum (Jord.) Rouy Geranium robertianum f. minutiflorum Geranium purpureum var. forsteri (Jord.) Merino Geranium robertianum var. minutiflorum (Jord.) St.-Lag. Geranium robertianum f. modestum Wilmott (Fourr.) F.N.Williams Geranium robertianum var. modestum (Fourr.) St.-Lag. Geranium robertianum subvar. modestum Geranium purpureum subsp. forsteri (Fourr.) Litard. Geranium robertianum var. parviflorum Viv. Geranium mediterraneum (Wilmott) H.G.Baker Hornem. Geranium robertianum f. subeglandulosum H.Lindb. Geranium robertianum var. villarsianum Geranium purpureum var. intricatum (Jord.) Rouy & Foucaud Geranium semiglabrum Jord. ex Boreau Geranium simile (Gren. ex Rouy) Graebn. Jord. ex Nyman Geranium villarsianum Jord. Robertium minutiflorum Geranium purpureum var. mediterraneum (Jord.) Fourr. Robertium modestum Fourr. Geranium eginense Jord. (Jord.) Graebn. (Jord. ex Boreau) Fourr. Robertium simile Fourr. Geranium purpureum var. minutiflorum (Jord.) Loret & Barrandon Geranium purpureum var. modestum Geranium minutiflorum (Fourr.) Hausskn. Geranium purpureum var. modestum (Fourr.) Nyman Geranium purpureum f. subeglandulosum Jord. H.Lindb. Geranium robertianum var. incisum A.St.-Hil. Geranium robertianum f. intricatum Geranium modestum (Gren. ex Rouy) Merino Geranium robertianum var. intricatum Gren. ex Rouy Robertium semiglabrum Geranium robertianum var. rubricaule

Geranium purpureum, the little-robin, is a species of flowering plant in the geranium family Geraniaceae. It is native to Europe, Africa, and western Asia, and introduced on all continents except Antarctica. It is similar in appearance to Geranium robertianum, a close relative.

Description

Geranium purpureum is an annual (sometimes biennial), herbaceous, flowering plant. It has small flowers with 5 sepals and 5 petals, each petal being 6.3–8.4 mm long and 1.5–2.0 mm wide. The flower has 10 stamens, each with a yellow anther. In the center of the flower, a single fused style supports 5 stigmas. The fruit is a schizocarp, which splits into 5 one-seeded mericarps at maturity.

Identification

Flower with corolla approximately 7 mm in diameter

Geranium purpureum is often confused with Geranium robertianum, a close relative. The primary character that distinguishes the two species is flower size. The corolla of Geranium purpureum is approximately 7.5 mm in diameter while that of Geranium robertianum is at least twice that size (15–20 mm). (For comparison, a U.S. dime is approximately 18 mm in diameter.) An identification key for genus Geranium in California distinguishes the two species as follows:

• Geranium purpureum: Petals (5.3–)6.3–8.4(–9.9) mm long, (0.8–)1.5–2.0(–2.6) mm wide; anthers yellow; middle leaf segment 5–20(–38)-lobed in distal half; mericarp with 1–4 collar-like rings at tip
• Geranium robertianum: Petals (8.5–)10.5–12.5(–14.2) mm long, (2.1–)2.6–4.5(–6.1) mm wide; anthers purplish; middle leaf segment 16–37(–49)-lobed in distal half; mericarp with 1–2(–3) collar-like rings at tip

Other keys emphasize the hairs on the sepals as a distinguishing characteristic. All keys include anther color but since both species have yellow pollen, plants can be difficult to distinguish based on anther color alone. Geranium purpureum and Geranium robertianum have chromosome numbers 2n = 32 and 2n = 64, respectively.

Taxonomy

Illustration of Geranium purpureum (lower righthand corner) published by Villars in 1789

Geranium purpureum was first described and named by the French botanist Domínique Villars in February 1786. A second description was published by Villars in June of the same year. Taken together, he described a plant growing on the rocks with red leaves and a tiny reddish-pink corolla. In 1788, he further described the leaves as pinnately lobed with 5 segments. Finally he published an illustration of Geranium purpureum in 1789.

Geranium purpureum Vill. is a member of Geranium section Ruberta in family Geraniaceae. As of September 2025, the name Geranium purpureum Vill. is widely accepted. Some authorities accept the name Geranium robertianum subsp. purpureum (Vill.) Nyman, a homotypic synonym of Geranium purpureum Vill.

Distribution and habitat

Geranium purpureum growing along the tracks at the Wien Floridsdorf railway station in Vienna

Geranium purpureum ranges from Great Britain southeastward to the Caucasus, with native populations occurring as far south as central Africa. Non-native populations occur on all continents except Antarctica. Introduced populations are often found along railway corridors.

Ecology

Geranium purpureum can not survive winters with an average January temperature of 4 °C (39 °F) or less.