Taxonomy

Senecio madagascariensis Poir., Encycl. [J. Lamarck & al.] Suppl. 5. 130. 1817.

Common name

Fireweed

Description

Propagule or dispersal unit is the fruit with pappus. Fertile part 1.5-2.2 mm long, 0.3-0.5 mm wide, in side view widest in the middle, +/- straight, rarely conspicuously curved, the upper (apical) end narrowing, in cross-section round (terete), basal scar (carpopodium) pronounced and well-differentiated or inconspicuous and undifferentiated, central, beak (=thinner sterile stalk between seed and pappus) absent, wings absent, fruit surface light brown or straw, smooth (except at cellular level), with simple straight hairs, thickened margin absent, longitudinal ribs present, 9-13, their surfaces smooth, with no hairs (glabrous).

Pappus type bristles / hairs, pappus elements all +/- similar, up to 3-6 mm long, in one (?) row, pappus elements numerous, elements falling off individually, the individual bristles rough / serrated (barbellate), rarely smooth (by misinterpretation), +/- equal width along length, white / translucent.

Notes: The pappus bristles are deciduous and will consequently most likely be missing in most cases when this species is encountered. The fruits of the various Senecio species are very similar. Of the two in this key, S. madagascariensis has the slightly smaller ones, with the fertile part up to 2 mm long as opposed to 2 mm or more. Note, however, that the genus has hundreds of other species that are not covered in the key.

Ecology

Short-lived perennial or annual, fruits wind-dispersed but presumably limited in distance due to early loss of pappus hairs. Tolerant of a variety of conditions but not of waterlogged soils. Disturbed areas, agricultural land, managed forests, plantations, orchards, grasslands, rail- and roadsides, urban areas.

Native range

Mozambique, South Africa, Swaziland, Madagascar.

Introduced range

United States (Hawai'i), Colombia, Brazil, Uruguay, Argentina, Kenya, Mauritius, Reunion, Australia.

Weed status within Australia

Weed of National Significance (WONS); Qld Restricted Invasive Plant Cat. 3; NT Category C; NSW Class 3 Regionally or Class 4 Locally Controlled Weed; SA Category 2 Declared Weed; WA Declared Pest s12 (C1 Prohibited).

Past interceptions (Australia): origins

Other or unidentified species of the genus from Canada, United States, Costa Rica, Colombia, Ecuador, United Kingdom, Netherlands, Germany, Czech Republic, Italy, Ethiopia, Tanzania, India, China, Korea, Japan, Thailand, Papua New Guinea, Vanuatu, New Caledonia.

Past interceptions (Australia): commodities

Containers.

Other or unidentified species of the genus also in/on agricultural machinery, machinery and parts, timber pallets, dried leaves, stone products, cut flowers, nursery stock, seeds for sowing, containers, used tyres, used vehicles, woven baskets.