Senecio madagascariensis

Name and classification

Senecio madagascariensis Poir.
Family Asteraceae, Tribe Senecioneae

NOTE: Very few fruits (less than ten) of Senecio madagascariensis were available for examination. Therefore, the description and images in this fact sheet may not be representative of this species’ fruits.

Common names

fireweed, Madagascar ragwort

Disseminule

fruit

Description

Fruit an achene, elliptic, straight to somewhat curved, 1.4–2.75 mm long, 0.3–0.6 mm in diameter; cross-section +/– terete; surface green when young, brown at maturity, sparsely pubescent in several (ca. 9) rows along the length of the fruit. Scar basal, cup-shaped. Pappus white, 2–3 times as long as achene, easily deciduous, often absent, leaving a white apical collar. Style base white, sometimes protruding beyond the apical collar. Embryo spatulate; endosperm absent.

Identification considerations

Fruits of various species of this genus look similar and may not be identifiable to species. Outside of its native distribution, Senecio madagascariensis is most likely to be confused with the closely related invasive weed, S. inaequidens, or the widespread species, S. vulgaris. Based on the limited numbers of achenes that were examined, S. inaequidens has the thickest rows of pubescence along the length of its fruit and the longest trichomes, S. madagascariensis has the sparsest rows and shortest trichomes, and S. vulgaris is intermediate for these characters.

Similar species

Senecio inaequidens Poir.

Senecio vulgaris L. (non-FNW)

Distribution

native to Madagascar and southern Africa

a noxious weed in Australia, Argentina and Hawaii, United States

Habitat

Subhumid to humid subtropical woodland on a wide range of soils. In Australia, it is an opportunistic invader of degraded pastures and disturbed sites, and can withstand drought conditions.

General information

Senecio madagascariensis is an annual or short-lived perennial herb to shrub. It can reproduce vegetatively, but mostly spreads via the wind-dispersal of its fruits. Possible methods of international dispersal include attachment to the surface of seafreight containers or railway cars or in the tire treads of road vehicles. Introduction to Australia is believed to have occurred via ballast water. Some scientists believe that S. inaequidens and S. madagascariensis are the same species; others consider them as part of the S. inaequidens complex, which includes both diploid and tetraploid populations.

achene without pappus

achene without pappus

herbarium specimen

herbarium specimen

achene surface, detail

achene surface, detail

apex showing stylar remains

apex showing stylar remains

apex showing stylar scar

apex showing stylar scar