Fireweed (Senecio madagascariensis) is an annual or a short-lived perennial that can vary greatly in size and shape depending on environmental conditions. In dry, harsh conditions it may be less than 20 cm tall with narrow leaves, no branching and few flowers. In ideal conditions it will grow to 50 cm tall with multiple branches, long wide leaves (6 cm x 2 cm) and about 100 flowers. The leaves are alternate and sessile. The blade of the leaf is 2 – 6 cm long and dark green with serrated margins. The leaf base tapers and clasps the stem, often with ear-like lobes in the upper branches. Flower heads are in loosely aggregations and are bright yellow, radiate, and 3.5 – 4 mm in diameter. There are 13 – 15 marginal (ray) florets per head with the rays (‘petals’) 6-10 mm long. ‘Seeds’ (achenes) are up to 100 per head, and are cylindrical, 2 – 3 mm long and surmounted by a pappus of silky hairs 4 – 6.5 mm long