What Does It Look Like?
What is it?
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 (Land Protection 2006; PlantNET 2007)
For further information and assistance with identification of Fireweed contact the herbarium in your state or territory.
Growth form (weed type/habit)
Where it currently grows? Preferred habitat
Fireweed is generally found on roadsides, in pasture, and adjacent open forest and prefers areas of bare soil to become established. It needs moist conditions for seedling establishment, but will grow and flower at any time of year other than mid-winter, given the rainfall. From germination to flowering can take as little as 6 weeks. Plants behave as annuals in southern areas, because they are frost tender, but may over-winter and behave as short-lived perennials further north (Miles undated).
Are there similar species?
There are many other weedy yellow daisies. Most of these consist of a single basal rosette and flower stalks arising from the centre, rather than having a bushy, branched habit. Their flowers tend to be a deeper yellow than those of Fireweed (Miles undated; PlantNET 2007).
There are also numerous native herbs in the genus Senecio. Among these, Fireweed can be distinguished by its 13-15 'petals', and fibrous root system. Two very similar natives are Senecio pinnatifolius var. maritimus which occurs on sea cliffs and dunes and has fleshier leaves and a taproot, and S. pinnatifolius var. lanceolatus which occurs in wet grassy forest along the top of the coastal escarpment. The latter has a more spreading, lax habit than the weed and slightly larger flowers. Senecio madagascariensis may also occur behind beaches or on top of the escarpment, so check the appearance of the plant as well as the location before making an identification (Miles undated; PlantNET 2007).
The large clumping native perennial, Senecio linearifolius, can behave in a weedy way around the edges of the farming areas, where it colonises after fire or other disturbance. If in doubt, get a specimen professionally identified (Miles undated; PlantNET 2007).