Stellaria pallida

Stellaria pallida
File:Stellaria pallida W.jpg
Stellaria pallida
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Eudicots
(unranked):	Core eudicots
Order:	Caryophyllales
Family:	Caryophyllaceae
Genus:	Stellaria
Species:	S. pallida
Binomial name
Stellaria pallida (Dumort.) Piré
Synonyms
Alsine pallida Dumort. S. apetala auct.

Stellaria pallida, commonly known as lesser chickweed, is an annual herbaceous plant in the flowering plant family Caryophyllaceae. It is native to Europe and is an introduced species in North America.

Taxonomy

Stellaria pallida forms part of a complex that also includes S. media and S. neglecta.

It is supposed that Stellaria pallida is the species that was described by Ucria in 1796 as Alsine petala. In 1828, Du Mortier, describing a form found in Belgium, applied the name Alsine pallida, which Piré (1863) transferred to the genus Stellaria.

The taxonomic status of Stellaria pallida (Dumort.) Piré has remained confused. Dandy (1958) and Clapham, Tutin and Warburg (1962) adopted this name, but while Clapham et al. treated S. apetala Ucria as a synonym, Dandy considered this to be a synonym of S. media L., as also did Chater and Heywood. Whitehead and Sinha, having failed to locate any specimens matching the description in the Flora Europaea, concluded that S. apetala Ucria or S. apetala auct. can be regarded as synonyms of S. pallida (Dumort.) Piré. This conclusion is now reflected in the online version of the Flora Europaea.

Description

Stellaria pallida is a much-branched herb, generally yellowish-green in colour. The stems are prostrate, usually 10–20 cm long, though some can reach 40 cm, and glabrous, with a single row of hairs between each pair of nodes. Leaves are pale-green and ovate, up to 1.5 cm long and usually less than 0.7 cm broad; proximal leaves have a short stalk, distal leaves are sessile.

The flowers are borne in terminal inflorescences of between 3 and 6 cymes. Flowers are small, 2–3 mm in diameter, and never open widely. There are four or five green sepals, lanceolate and 2–3.5 mm long. Petals are usually absent, or, if present, are minute. There are usually between one and three stamens, sometimes none, with grey-violet anthers, and three styles.

The numerous seeds are pale yellowish-brown, occasionally darker, 0.6–0.8 mm in diameter, with prominent small, blunt tubercles.

Stellaria pallida is self-pollinating and, because the flowers do not open widely, is often cleistogamous.

Distribution

Stellaria pallida has a widespread, though local, distribution across Europe, from southern Spain and the Mediterranean islands to Lapland, and from the British Isles to Ukraine. In North America it is found as an introduced species from Ontario, Canada, to Mexico and throughout the United States, from the east coast (Virginia, North and South Carolina, and Florida) to the west coast (California and Washington).

Habitat

Stellaria pallida is usually found on coastal sand dunes, in sandy waste places, or on cultivated sandy soils. In Europe it is often found growing under the shade of Scots Pine in woodland on light glacial sands.

Similar species

The apetalous form of Stellaria media, var. apetala Gaudin, and S. pallida are superficially similar and are easily confused. A combination of morphological characters is usually required to separate them, the most useful including overall colour (media is darker green), size of leaves and sepals (media is larger), number of stamens (pallida has 1-3, media has 3-10), colour of anthers (grey-violet in pallida, red-violet in media), and colour and size of seeds (yellowish-brown, ≤ 0.8 mm in pallida; dark-reddish-brown and ≥ 0.9 mm in media).