Weed Identification

Australia > > Fireweed

Fireweed

Senecio madagascariensis

Family: Asteraceae.

Form: Herb

Origin: Native of South Africa.

Flowers/Seedhead: Inflorescence a loose cluster of flowerheads. Flowers all year, chiefly autumn to late spring.

Description: Mostly erect annual or biennial herb to 70 cm high. Leaves variable, to 8 cm long and to1.5 cm wide.

Distinguishing features: Distinguished by lanceolate to elliptic leaves that are not deeply dissected; bracts around flowerheads (involucral bracts) 19–21 in one row, these bracts to 6 mm long; 12–15 petal-like yellow ray florets with strap-like parts to 1 cm long; seeds to 2.5 mm long topped by hairs (pappus) to 6.5 mm long.

Dispersal: Most spread is by wind dispersed seed. Long distance dispersal also occurs by seeds on animals, in stock feed or in mud on vehicles.

Confused With: Small plants of Variable Groundsel, Senecio lautus ssp. dissectifolius (with 19–21involucral bracts) that are not large enough to have dissected leaves .


19–21 bracts around flowerheads
Stroud, NSW, Aug
photo J.R.Hosking

Notes: Serious weed particularly of coastal pastures in eastern Australia where it covers thousands of hectares. First recorded in the lower Hunter Valley in 1918. Losses result from decreased pasture production and reductions in growth rates, or death, of cattle and horses caused bypyrrolizidine alkaloids occurring in the plant. Native insects and diseases found on native Senecio also cause death of Fireweed plants.

References:

    Biology of Australian Weeds. F. Panetta et al., (eds), Vol. 2, 1998, pages 247–267. Noxious Weeds of Australia. W. Parsons and E. Cuthbertson, 1992, pages 304–305.

Web References: Search Australian web sites for further information on this weed.

Seedling, Silverwater, NSW, May
Covering hillside, Gloucester region
NSW, August
photo J.R.Hosking

This weed has been included in the WEEDeck field guide as card H09

More information about WEEDeck is available from Sainty & Associates Pty. Ltd.

 

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