Fireweed

Senecio madagascariensis Poir.

Synonyms -

Family: Asteraceae

Names:

Senecio is from the Latin senex meaning old man and refers to the beard like pappus on the seed.
Madagascariensis refers to Madagascar where the plant was first collected or originated.
Fireweed is a common name of several number of plants in the Senecio genus and probably refers to their prevalence following fire.

Other Names:

Madagascar Groundsel
Madagascar Ragwort

Summary:

Senecio madagascariensis (Fireweed) is an annual to short lived perennial, erect herb that normally grows 10 to 70 cm high. The leaves are 2-7 cm long and are entire or have lobed or toothed margins. The yellow daisy-like flower heads are loosely clustered. Each flower head is surrounded by 19-21 greenish involucral bracts. The outer 12-15 florets have radiating petal-like blades 6-10 mm long while the numerous inner florets are tubular. The tiny fruits are topped by a tuft of many white bristles.
Fireweed is native to South Africa and now a weed of degraded pasture, open bushland, roadsides and disturbed areas of eastern Australia. Fireweed is toxic to stock. It flowers from spring to autumn.

Description:

Cotyledons:

Two.

First leaves:

Leaves:

Alternate, bright green, variable size and shape, somewhat fleshy, stem clasping
Stipules - None.
Petiole - None.
Blade - Narrow and 10-60(80) mm long. Smooth serrated or lobed edges.
Stem leaves - Clasp the stem.

Stems:

Erect, 100-700 mm tall, slender, 1 to many arising from the crown, branching above.
Flower stem - Branched with terminal clusters of flowers.

Flower head:

Terminal cluster of daisy like (composite) flowers.
There are 20-21 bracts (phyllaries) surrounding the flower head.

Flowers:

Bright yellow, composite flower, 15-20 mm diameter with 13 yellow ray "petals" surrounding the yellow disc florets. 1 to 200 "flowers" per plant.
Ovary -
"Petals" - 13 ray florets, oblong to egg shaped, 10 mm long.
Disc florets - Yellow, many, tubular
Stamens -
Anthers -

Fruit:

Each flower head produces 50-150 seeds.

Seeds:

Brownish, cylindrical, slender, 1-3 mm long with short, white hairs in longitudinal lines and crowned with a pappus of feathery, white, silky hairs. Pappus hairs 4.5-6 mm long.

Roots:

Shallow branching annual or perennial taproot with numerous fibrous laterals all in the top 200 mm of soil.

Key Characters:

20-21 bracts (phyllaries) surrounding the flower head.
13 ray florets.

Biology:

Life cycle:

Annual, biennial or short lived perennial herb.
Seeds germinate at any time of the year when moisture is present with the main germinations occurring between March and June. Most seedlings for the year have established by the end of May. The seedlings grow rapidly and flowering commences within 6-10 weeks and continues until mid summer. The top growth dies off in the heat of summer and the plant dies or regenerates in early autumn. In mild conditions the plant may grow throughout summer and produce a flush of new growth in autumn. Most plants die each year but some may survive for up to 3 years. In many areas all life forms, seedlings, vegetative and flowering plants may be found at any one time however there is a flush of germination in autumn with a flush of flowering in spring.
Rainfall when temperatures are between 15 and 270C will cause a germination flush. Seed buried more than 2 cm deep is less likely to germinate and buried seed may survive for over 10 years in the soil. It is possible to have several generations in a single year.
It has a variable leaf structure and growth habit but it is commonly a low, heavily branched annual or short lived perennial.
The density of Fireweed varies from year to year depending on seasonal conditions.

Physiology:

Drought tolerant.
Susceptible to frost.
Waterlogging sensitive.
Prefers full sun situations.

Reproduction:

From the crown and from seed.

Flowering times:

Spring to summer.

Seed Biology and Germination:

Plants typically produce 5,000-30,000 seeds per year.
It forms a persistent seed bank in the soil. Seed may remain dormant in the soil for 10 years. Approximately 15% of the seed will be dormant initially.
Seed germinates in light at temperatures between 10 an 35 degrees C with an optima between 15-27 degrees C.
Most seed can germinate as soon as it is released from the flower head.
The pappus detaches easily reducing the distance and conditions where seed is spread by wind.

Vegetative Propagules:

Hybrids:

Allelopathy:

Population Dynamics and Dispersal:

Often invades pastures following drought.
Local spread is by wind with most seed falling with in 5 m to the parent plant. The pappus detaches easily and most of material seen in the air is pappus without seed. Stems may form roots where they contact the soil
Medium distance spread in mainly on animals and birds and agricultural operations.
Long distance spread is mainly by contaminated produce and on vehicles.

Origin and History:

Native of South Africa and prevalent in Madagascar and South America.
It was first recorded in Australia in the Hunter Valley, NSW in 1918 and has spread along the east coast since then. It was declared a weed of National Significance in 2012.

Distribution:

ACT, NSW, QLD, SA, VIC.

Courtesy Australia's Virtual Herbarium.
Frost probably determines the distribution by both direct effects and leaving the frost affected plants more susceptible to disease.

Habitats:

Humid to sub humid tropical woodlands.
Disturbed or cultivated areas, poorly managed pastures and roadsides.
Prefers open full sun areas.

Climate:

Temperate, humid subtropics and sub humid subtropics.
Relatively frost free areas.

Soil:

Occurs on a wide range of soils from fertile self mulching clays to acid sands.
It is most prolific on low to medium fertility, well drained, acid sands. It rarely survives in waterlogged soils.

Plant Associations:

Significance:

Beneficial:

Detrimental:

Weed of pasture, cultivation, disturbed areas, stock camps and bushland.
Difficult to control.
Toxic to horses and cattle.
Often causes ill thrift in other grazing stock.
It reduces the profitability of grazing by reducing both pasture production and livestock growth rates.

Toxicity:

Toxic to horses, cattle and alpacas. Sheep and goats are about 20 times more tolerant than cattle because they have rumen organisms that can detoxify the toxin. However deaths have been reported. All parts of the plant at all stages are toxic. Hay, silage and grain contaminated with Fireweed plants or seeds can also be toxic.
Death and ill thrift of stock grazing infested pastures is attributed to pyrrolizidine alkaloids.

Symptoms:

Liver damage, jaundice, low growth rates, loss of condition chronic scouring, aimless wandering, muscular incoordination, apparent blindness, photosensitisation, abdominal straining, rectal prolapse and nervous symptoms due to brain damage. Sudden death can also occur in apparently healthy animals 3-6 months after grazing Fireweed.
Mineral deficiencies and internal parasites can give similar symptoms.

Treatment:

Remove stock from infested areas.

Legislation:

Declared weed in all states. Weed of National Significance.

Management and Control:

Difficult to control physically because stems may form roots where they contact the soil and is has a perennial rootstock.
Prevent Fireweed from setting seed. avoid bringing in contaminated feed and seed. Clean vehicles and machinery that have been in Fireweed areas.
Cultivate in autumn to help kill roots and use glyphosate as the plant herbicide for a few years of cropping and spray with clopyralid in cereals or canola.
Sow a competitive pasture such as ryegrass plus a legume (or apply N). Graze and fertilise grazed areas to main a dense gap free sward especially in autumn. Encourage perennial pastures if possible. Cattle and horse avoid eating Fireweed which favours it. Rotationally graze with goat or Merino wethers if possible
Rope wick applicators with 1 part glyphosate to 2 parts water and using a double pass can be used to control fireweed that is taller than the pasture.
In bushland situations, encouraging tall growing species to increase the level of shade will normally provide adequate control.
Bromoxynil or Jaguar® can be used in legume based pastures and Grazon®, fluroxypyr or metsulfuron can be used in grass pastures. June is the best time to apply these when most of the seedlings have emerged but they are not too big. More than one application per year may be required in some areas or seasons.
Slashing is not very effective and may increase the likelihood of poisoning or forcing plants into a perennial growth pattern.

Thresholds:

Eradication strategies:

Mouldboard plough to 200 mm deep and keep all subsequent cultivations shallower to avoid returning dormant see to the surface.
Spot spray individual plants with a mixture of 100 mL Grazon® (or equivalent) plus 2.5 mL Pulse® in 10 L water. This will kill the parent plant while leaving the grasses and leave a soil residual herbicide in the soil to control seedling for the next year or so.
Use a fork to remove single plants including the rootstock.

Herbicide resistance:

None reported.

Biological Control:

Biocontrol is being investigated.

Related plants:

African Daisy (Senecio pterophorus)
Bushy Groundsel (Senecio cunninghamii)
Canary Creeper (Senecio angulatus = S. tamoides) is a scrambling vine with broader leaves, fewer involucral bracts and fewer outer florets.
Cape Ivy (Senecio mikanioides = Delairea odorata) is a scrambling vine.
Commonwealth weed (Senecio bipinnatisectus)
Cotton Fireweed (Senecio quadridentatus)
Feathery Groundsel (Senecio anethifolius)
Fireweed (Senecio lautus)
Fireweed Groundsel (Senecio linearifolius)
Fleshy Groundsel (Senecio gregorii)
Hispid Fireweed (Senecio hispidulus)
Holly-leaved Senecio (Senecio glastifolius)
Mountain Fireweed (Senecio gunnii)
Purple Groundsel (Senecio elegans)
Ragwort (Senecio jacobaea)
Slender Groundsel (Senecio glossanthus)
Squarrose Fireweed (Senecio squarrosus)
Tall Groundsel (Senecio runcinifolius)
Tall Yellowtop (Senecio magnificus)
Senecio daltonii
Senecio madagascariensis
Senecio megaglossus

Plants of similar appearance:

Fireweed is very similar to the native Senecio condylus (Variable Groundsel) which has also been known as Senecio lautus. Variable Groundsel, although native can also be somewhat weedy in nature being a disturbance opportunist and is commonly found along road verges and in bushland following fire. Variable groundsel has leaves which are commonly deeply dissected but may also be entire or toothed to lobed like those of fireweed; 12-20 involucral bracts (rather than 19-21 in fireweed); 8-14 outer florets with blades 8-12 mm long (rather than 13-15 outer florets with blades 6-10 mm long in fireweed).
Another native called Variable Groundsel (Senecio pinnatifolius) which occurs in coastal areas all around southern Australia looks similar but generally occurs in bushland situations.

References:

Auld, B.A. and Medd R.W. (1992). Weeds. An illustrated botanical guide to the weeds of Australia. (Inkata Press, Melbourne). P113. Photo.

Bodkin, F. (1986). Encyclopaedia Botanica. (Angus and Robertson, Australia).

Burbidge, N.T. and Gray, M. (1970). Flora of the Australian Capital Territory. (Australian National University Press, Canberra).

Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne).

Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney).

Harden, Gwen J. (1991). Flora of NSW. (Royal Botanic Gardens, Sydney). Volume . P. Diagram.

Lazarides, M. and Cowley, K. and Hohnen, P. (1997). CSIRO handbook of Australian Weeds. (CSIRO, Melbourne). #919.13

Moore, J.H. and Wheeler, J.R. (2013). Southern Weeds and their Control. (Second Edition). South Coast NRM and Department of Agriculture and Food Western Australia. P. Photos.

Parsons, W.T. and Cuthbertson, E.G. (1992) Noxious weeds of Australia. (Inkata Press, Melbourne). P304-305. Photos.

Randall, J.M. and Marinelli, J. (1996) Invasive Plants. (Brooklyn Botanic Gardens Inc. Brooklyn). P. Photo.

Acknowledgments:

Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.