Senecio jacobaea L.
Senecio is from the Latin senex meaning old man and refers to the beard like pappus on the seed.
Jacobaea was the name of a group of plants that are now included in the Senecio genus.
Ragwort is from ragged referring to the ragged leaves and wort is from the Old English wyrt meaning medicinal herb or more generally a weed.
Other names:St. James Wort (Europe)
Tansy Ragwort (North America)
Summary:An erect perennial shrub to 1.5 m with annual tops carrying dense, terminal, clusters of bright yellow, daisy type flowers from summer to autumn and much divided ragged leaves that are usually hairless.
Two. 10-15 mm overall in length with a short petiole. Hairless. The seedling has a very short hypocotyl but no epicotyl.
First Leaves:The leaves develop singly and the first leaf is 15-20 mm long overall with a short petiole. Generally it is hairless and has a smooth edge.
Leaves:Forms a rosette that withers before flowering.
Petiole - Long (usually 10-30 mm) on the lower and shorter to none on the upper leaves.
Blade - Up to 350 mm but usually 60-120 mm long x 20-60 mm wide, dark green on the upper surface and paler below, wrinkled, deeply lobed with the terminal lobe larger than the side lobes. The lobes are narrow or egg shaped and have wavy, toothed edges. Hairless or sparsely hairy on the upper surface and often downy hairy on the lower surface.
Stem leaves - Lower stem leaves are petiolate while the upper stem leaves are 75-200 mm in length, stalkless and clasping, oblong to egg shaped in outline and deeply lobed with the lobes irregularly toothed or lobed. Almost hairless or cobwebby hairs on the upper and lower surfaces especially on the young leaves.
Stems: One to many, erect, 300-2000 mm high and usually about 500 mm tall, circular in cross section with shallow fluting, stout, solid and pithy, and dark or reddish-purple at the base with dark longitudinal striations on the upper portion. Branching above the middle and rarely from lower down. Perennial plants usually have many stems emerging from the roots. Very short and cobwebby long hairs initially becoming almost hairless with age.
Flower head:Numerous daisy type flowers at the ends of branches crowded in a compound corymb surrounded by about 13 bracts and 2-6 bracteoles.
Flowers: Yellow, daisy type, 15-25 mm in diameter and have a single row of 12-15 petalled (ray) florets with 6-9 mm long 'petals' (ligules).
Bracts - About 13, oblong to narrowly egg shaped, 4-5 mm long. Tips brown or black and pointed. Outer bracts short, awl shaped and well separated.
Florets - Ray florets, 12-15, yellow, with 3-toothed 'petals'. Disk florets, about 40, yellow, 5-toothed
'Petals' - Yellow in a single row around the edge, 3 toothed tip.
Fruit:Achene, 1.5-3 mm long, light brown, striped. Two types of achene; those from ray florets are smooth and hairless and those from disk florets have short low lying hairs. Pappus of long, slender, feathery, white silky bristles, 4-6 mm long and at least twice as long as the achene and only persist on the disk florets.
Seeds:Enclosed in the fruit.
Roots:Short, thick, creeping rootstock (rhizome) with many almost fleshy roots about 150 mm long. Fibrous feeder roots penetrate deep into the soil.
Key Characters:Erect perennial.
Stems woody towards the base.
Leaves pinnatisect with coarsely toothed lobes.
Flowers, 18-50, nearly twice as long as the involucre, homogamous, discoid, all tubular, all bisexual, yellow.
Involucre bracts about 12.
Adapted from J.M. Black.
Biennial or short lived perennial or rarely annual. Seeds germinate from spring to autumn, with a peak in autumn, and grow slowly to form a rosette of leaves about 50 mm wide by summer on a strong rootstock. This continues forming leaves over the next autumn, winter and spring producing a 'cabbage' type of growth. In spring, flowering stems emerge around November and flowering occurs from late summer to early autumn. Seeds are ripe within a few weeks of flowering. The plants normally die after flowering or the flowering stems die back leaving the perennial crown. Some plants may take several years before flowering or may even die in the 'cabbage' stage before they flower and others may complete there life cycle in a single season. However, most are biennial and take 2 seasons to complete there life cycle. Plants which suffer mechanical or chemical damage from early to mid flowering which interferes with their normal life cycle are liable to become perennial in habit and flower for several seasons.
Physiology:Intolerant of shade.
Reproduction:By seed and rootstock.
Flowering times:Autumn in NSW.
Summer to autumn in SA.
Summer in WA.
Seed Biology and Germination:Little or no dormancy.
Seed germinates in horse dung from horses fed on contaminated feed.
A multi stemmed plant can produce 250,000 seeds per year.
Seed viability is often around 80%.
It does not germinate when buried more than 25 mm deep and will last buried in the soil for over 8 years.
Maximum germination is from seed on the soil surface.
Seed viability drops to 1% after 4 years on the surface and 10-16 years if buried 40 mm or more deep.
Hybrids:Small headed and large headed forms.
Allelopathy:Population Dynamics and Dispersal:
Spread mainly by seed. Some seed is wind borne but most of the "Ragwort seed" seen blowing in the wind consists of pappus that has dropped its seed. In humid conditions that are common in infested areas, the pappus does not open sufficiently to provide enough buoyancy for effective wind dispersal. Field evidence indicates that it may spread several kilometres by wind. In experiments most seed falls within 5-20 metres of the parent plant and a few travel more than 37-100 metres. It is carried in water and survives long periods of immersion. Seed is also spread by attachment to wool and fur of animals and to vehicles and machinery. It is spread as a contaminant of hay and chaff.
Ragwort is a vigorous and invasive species of disturbed and denuded areas and it tends to form almost exclusive stands of Ragwort if allowed to establish.
Areas in which the forest cover has been removed and not replaced by well managed pasture or crops are particularly vulnerable to invasion.
Origin and History:Europe. Siberia. North west India.
First recorded in Victoria in 1852, Tasmania in 1857, WA in 1940, SA in 1954.
Its occurrence around timber mills in WA and Victoria is probably due to importation of contaminated chaff.
Distribution:NSW, SA, TAS, VIC, WA.
In Tasmania, it mainly a weed of the North West and is also present in the North East and in the South, and is still extending its range in areas which offer a suitable habitat. It occurs in small numbers in pasture but does not normally become important where this is well managed.
Serious weed on New Zealand pastures.
Courtesy Australia's Virtual Herbarium.
Temperate. Humid temperate areas.
Most abundant in areas with an annual rainfall greater than 750 mm.
Soil:It occurs over a wide range of soils and fertility levels.
Most abundant on heavy soils of high fertility.
Plant Associations:It doesn't establish in shaded situations such as forests.
More abundant in cattle pastures than sheep pastures.
Common on areas that have been cleared but not sown to pasture.
Significance:Infests 820,000 ha in Victoria.
Beneficial:Used as a dye plant.
Used in herbal medicine for cough, colds, internal parasites, rheumatism, cramp, ulcers, wounds, sprains and as a stimulant tonic. It is still commercially available despite its questionable safety.
Detrimental:Weed of pastures, lucerne, neglected areas, river flats and disturbed areas.
It has attracted attention that is out of proportion to its economic importance.
Toxicity:Causes liver damage (cirrhosis) or Seneciosis in stock after long term grazing. In horses it is called Winton disease because it was first described at Winton in NZ. It is very similar to toxicity caused by Crotalaria, Heliotrope and Amsinckia.
Horses and cattle are the most sensitive, sheep and goats are ten times more tolerant. Few field cases reported in Australia but fairly common in New Zealand.
Hay containing Ragwort can be toxic.
It contains alkaloids that may be carcinogenic and some alkaloids are carried into milk and honey. The taint in honey makes it unfit for direct sale.
Pollen may cause an allergenic reaction in some people.
Symptoms:Symptoms may not appear for weeks to a year after grazing Ragwort.
Dullness, loss of appetite, depraved appetite, diarrhoea, straining, staggering, excitability, jaundice, yellow whites of the eyes, apparent blindness, staring, photo-sensitisation, scabs on exposed skin, taint in milk, thirst, coma and death a few days after symptoms appear.
Noxious weed of NSW, SA, TAS, VIC and WA.
Management and Control:An integrated control program is required.
Increase pasture competition to reduce the survival of Ragwort seedlings (Thomson and Saunders, 1986). Nitrogen and phosphate applications reduce reinvasion of pastures. A combination of phosphate applications and 2,4-D resulted in the lowest levels of ragwort and better composition in NZ pastures (Rahman, 1990). Herbicides that damage the pasture such as glyphosate result in higher levels of seedling establishing after spraying.
Hormone herbicides such as 2,4-D are effective on seedlings and plants in the 'cabbage' phase but tend to fail once the flowering stem has emerged. Heavy stands should not be grazed after spraying because of the risk of poisoning animals.
Glyphosate is effective but tends to leave the area bare and prone to re-infestation.
Clopyralid, dicamba and Tordon® 75-D are more effective on old plants with strong crowns.
Rope wick or blanket wiper application of non selective herbicides can give good levels of control.
Heavy grazing with sheep or goats is also used. Animals that are destined for slaughter are preferred to avoid any future production losses due to liver damage that may occur after grazing.
Cultivation must be repeated regularly to be effective.
Manually remove isolated plants and their roots, to a depth of 200 mm, and spray a buffer area of 20 metres around the infestation with 1 part of Tordon® 75-D in 100 parts of water in spring to early summer.
Prevent seed set.
Mouldboard plough to 150 mm in spring, cultivate in summer and autumn, grow a cereal crop for two years, then establish competitive perennial pastures and fertilise well and graze with sheep or goats. Spray Graze in years when seedlings appear.
Plant the area to pine(Pinus radiata) or other tree species.
Herbicide resistance:Biological Control:
A number of bio control agents have been released and a number are under investigation. Some native insects also occasionally damage plants.
Related plants:African Daisy (Senecio pterophorus)
Bushy Groundsel (Senecio cunninghamii)
Canary Creeper (Senecio angulatus = S. tamoides)
Cape Ivy (Senecio mikanioides = Delairea odorata)
Common Groundsel. (Senecio vulgaris)
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)
Slender Groundsel (Senecio glossanthus)
Squarrose Fireweed (Senecio squarrosus)
Tall Groundsel (Senecio runcinifolius)
Tall Yellowtop (Senecio magnificus)
Plants of similar appearance:References:
Auld, B.A. and Medd R.W. (1992). Weeds. An illustrated botanical guide to the weeds of Australia. (Inkata Press, Melbourne). P112. Photo.
Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P886.
Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney). P178-181. Diagram.
Gardner, G.A. and Bennetts, H.W. (1956). The toxic plants of Western Australia. (West Australian Newspapers Ltd, Perth). P196-197. Diagram.
Harden, Gwen J. (1991). Flora of NSW. (Royal Botanic Gardens, Sydney). Volume 3. P312. Diagram.
Hussey, B.M.J., Keighery, G.J., Cousens, R.D., Dodd, J. and Lloyd, S.G. (1997). Western Weeds. A guide to the weeds of Western Australia. (Plant Protection Society of Western Australia, Perth, Western Australia). P104. Photo.
Hyde-Wyatt, B.H. and Morris, D.I. (1975). Tasmanian weed handbook. (Tasmanian Department of Agriculture, Hobart, Tasmania). P38-39. Diagrams.
Hyde-Wyatt, B.H. and Morris, D.I. (1980) The Noxious and Secondary Weeds of Tasmania. (Tasmanian Department of Agriculture, Hobart, Tasmania). P82-83. Diagrams.
Lamp, C. and Collet, F. (1990). A Field Guide to Weeds in Australia. (Inkata Press, Melbourne).
Lazarides, M. and Hince, B. (1993). CSIRO handbook of economic plants of Australia. (CSIRO, Melbourne). #1125.10.
Meadly, G.R.W. (1965). Weeds of Western Australia. (Department of Agriculture - Western Australia). P148-150. Diagrams. Photo.
Parsons, W.T. and Cuthbertson, E.G. (1992). Noxious weeds of Australia. (Inkata Press, Melbourne). P298-303.
Thomson and Saunders. (1986).
Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.