Introduced annual, biennial, or perennial forb to 70cm tall. Leaves alternating up the stems, flat, 2-12cm long, 3-25mm wide, hairless to sparsely hairy, margins entire to toothed or dissected and toothed. Uppermost leaves sometimes with toothed basal lobes. Flowers yellow, with 12-15 ‘petals’. Flower heads behind the 'petals' narrow bell-shaped, in open groups of 2-20 flower heads at the tops of the stems. A weed of national significance. Noxious weed in all of NSW.
This description mostly based on the description in Thompson, I.R., (2005) Taxonomic studies of Australian Senecio (Asteraceae) 5. The S. pinnatifolius/S. lautus complex. Muelleria 21: 30-31. Fig 3 page 32 (map), Fig. 4 page 33 (dried specimen)
Weeds of Australia Biosecurity Queensland Edition description: http://keyserver.lucidcentral.org/weeds/data/03030800-0b07-490a-8d04-0605030c0f01/media/Html/Senecio_madagascariensis.htm