Geranium purpureum


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, 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

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. An identification key for genus Geranium in California distinguishes the two species as follows:
  • Geranium purpureum: Petals 6.3–8.4 mm long, 1.5–2.0 mm wide; anthers yellow; middle leaf segment 5–20-lobed in distal half; mericarp with 1–4 collar-like rings at tip
  • Geranium robertianum: Petals 10.5–12.5 mm long, 2.6–4.5 mm wide; anthers purplish; middle leaf segment 16–37-lobed in distal half; mericarp with 1–2 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

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 is a member of Geranium section Ruberta in family Geraniaceae., the name Geranium purpureum is widely accepted. Some authorities accept the name Geranium robertianum subsp. purpureum, a homotypic synonym of ''Geranium purpureum''

Distribution and habitat

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 or less.