Quick Facts

Quick facts

• Ragwort (Senecio jacobaea) is naturally a biennial, but changes to a perennial if constantly cut.
• One plant can produce 250 000 achenes (1-seeded fruit) in a year.
• Achenes of 2 types: heavy ones to drop near to parent plant and regenerate locally, and lighter ones with that can be blown by the wind for distances of up to 80 metres or carried long distances by water
• Seeds can lay dormant for 20 years. At the end of that time 70% are still viable.
• Cutting / pulling when plants are flowering, even with immature flowers, can result in viable seed being shed.
• The establishment of good competition from pastures, crops or native vegetation is essential for the long-term management of Ragwort.

What Does It Look Like?

What is it?

Ragwort (Senecio jacobaea) is a biennial or short-lived perennial, erect herb, to about 1.5 metres tall more commonly 450–600 mm, slightly hairy, or smooth without hairs, reproducing from crowns, roots and seeds. Two types of leaves are produced; first the basal rosette of leaves; and subsequent stem leaves, showing great variability in leaf shape and and amount of division and lobes on different parts of the plant. The basal rosette leaves (laying flat or near flat on the ground in a whorl from the centre) are, ovate (egg-shaped attached at the wider end) in outline, to c. 200 mm long, with leaf-stalk (petiolate), slightly toothed to deeply lobed (pinnatisect), sometimes with those lobes having lobes (bipinnatissect) dark to mid-green on upper surface, paler and sometimes downy underneath and wrinkled. The lower leaves die off as the flowering stalk emerges. The stems are usually single but sometimes there will be several per plant with branching at the top of the plant, and sometimes bearing cobweb-like hairs. Stem leaves are un-stalked (sessile), also ovate in outline, 60–150 mm long, 30–80 mm wide, deeply divided sometimes with ear-shaped lobes, variably lacerated, lower lobes often divided to the mid-rib and lower lobes often separate from the rest of the leaf (DSE 2004; Faithfull & McLaren 2004).

The flower-heads are bright yellow, daisy-like, with may flower-heads grouped in inflorescence ( he group or arrangement of flowers on a plant) on stems at the top of the plant to about 300 mm in diameter, with many stems of inflorescence of flower-heads per plant. Each flower-head is about 25 mm in diameter with up to 65 yellow florets (flowers), including 10 to 15 ray florets on the outer edge bearing petal-like ligules, and the 30–50 disc inner florets, without a petal like structures. Surrounding the flowers are involucre bracts (small leaf like structures) that is cup-shaped 3.5–5 mm long, without hairs or sparsely cobwebbed at base There are 11–13, black-tipped bracts.

The fruits or 'seeds' (cypselas) in each flower-head has two types of 'seeds': those in the centre of the head are surmounted by a ring of fine, white, feathery hairs 4 to 5 mm long to aid wind dispersal and a have a covering of microscopic bristles which aid attachment to animals; those around the edge of the head (12-15/flower) are smooth, thicker and heavier than those of the disc and drop straight to the ground. There are commonly around 70 000 'seeds' per plant, but there may be up to 250 000 per plant. They are straw coloured to light brown and about 2 mm long and 0.5 mm wide (DSE 2004; Faithfull & McLaren 2004).

For further information and assistance with identification of Ragwort contact the herbarium in your state or territory.

Flower colour

Yellow

Growth form (weed type/habit)

Herb

Where it currently grows? Preferred habitat

Ragwort favours heavy soils of moderate fertility. The heaviest infestations occur on rather poor land which has been cleared in the past but never properly developed for agriculture, or on run-down pastures and grasslands. Pastures grazed by cattle are particularly prone to Ragwort invasion as the death of desirable plants from cattle hooves leaves openings for seedlings to establish. As cattle normally avoid grazing Ragwort it has a competitive advantage over other pasture plants that are grazed.

Ragwort will also invade dry coastal vegetation, heathland & heathy woodland, lowland grassland and grassy woodland, damp sclerophyll forest, wet sclerophyll forest, riparian vegetation, freshwater wetlands (DPIWE 2002; DSE 2004).

Are there similar species?

Native species of Senecio are often mistaken for Ragwort. Senecio species that Ragwort can be confused with are Common groundsel (Senecio vulgaris), Commonwealth Weed (Senecio bipinnatisectus), Variable Groundsel (Senecio lautus), Fireweed (Senecio madagascariensis), African Daisy (Senecio pterophorus) and Fireweed Groundsel (Senecio linearifolius) (Navie 2004).

See Navie (2004) for detailed differences between the species. If in doubt, contact the herbaria in your state or territory.

Why Is It A Weed?

What are its impacts?

Ragwort (Senecio jacobaea) was included in the list of 71 species that were nominated by state and territory governments for assessment as Weeds of National Significance (WoNS). Following an assessment process, Ragwort was not included as one of the 20 WoNS. However, it remains a weed of potential national significance. Ragwort is a serious agricultural and environmental weed. It is steadily invading pasture and native vegetation across southern Victoria.

Agriculture: Ragwort contains alkaloid toxins that, if eaten by horses or any grazing animal, can have debilitating or fatal consequences. The highest concentration of toxin is found in the pollen, then in order, the leaves, stems and roots. The effect of the toxin is cumulative and irrevocable, and as it builds up in the body results in liver failure. The build up is undetectable until it finally reaches the critical level at which symptoms occur (DPIWE 2002; AgResource 2006). Dairy cattle forced to eat Ragwort produce tainted milk (McLaren & Faithfull 2004). In addition to its health impacts, Ragwort is a major pasture weed particularly on land grazed by cattle and horses and on dairy farms. Dairy cattle forced to graze ragwort produce tainted milk. It produces dense foliage close to the ground which suppresses and prevents regeneration of other vegetation. Ragwort competes strongly with more desirable plants, reducing pasture productivity and the value of agricultural land, and can be invasive in forestry plantations (Agriculture Victoria 2021). The ability of each Ragwort plant to produce tens of thousands of seeds, combined with its capacity to regenerate from root or crown fragments, gives Ragwort an amazing capacity to spread. Once established, Ragwort can overwhelm pasture and reduce its livestock carrying capacity (DPIWE 2002; AgResource 2006).

Native ecosystems:  Ragwort can be invasive on roadsides, native forests and woodlands, threatening biodiversity in these areas.

Urban areas: Ragwort can also be invasive on roadsides, and on urban fringes.

How does it spread?

×Ragwort has a number of very effective means to ensure reproduction and survival. Each plant produces two types of 'seeds' called cypselas (1-seeded fruit), one type from the ray achenes; and another from disc achenes. The heavier ray achenes (10–15) fall close to the dying parent plant, with the bare ground left by the parent creating an ideal environment for the new seeds to germinate. In this way, Ragwort can quickly dominate an area. The disc achenes are lighter seeds (40–50), with a pappus (covering of bristle at the top of the seed, and are designed for long-distance dispersal. They are spread by the wind and in the coats of animals, by water, in stock feed or in mud attached to vehicles and machinery.

Ragwort is also able to re-grow from small fragments of root or crown (DSE 2004), moved in soil or on vehicles and machinery.

What is its history in Australia?

Ragwort has been recognised as a serious weed in Australia since late 19th century when it was first proclaimed under the Victorian Thistle Act 1890. It was probably introduced with fodder or animals, early in settlement (McLaren et al. 2000).

First collected in; Tasmania in 1895; Victoria in 1896; and new South Wales in 1938 (AVH 2021).

How To Manage It?

Best practice management

Ragwort (Senecio jacobaea) can be treated by chemical and physical means. Mechanical control is not always advisable, especially on established populations and this can break up and further spread roots that regrow in to new plants. Physical control involves handling Ragwort and operators must wear suitable protective clothing i.e. skin covered up, neoprene / rubber gloves, and pollen mask if the plants are flowering (DPIWE 2002) as the plant is potential toxic to humans and well as animals.

Chemical control: Effective chemical control requires a minimum 2-year spray eradication program with applications twice a year in the autumn and spring. Sprays should be targeted at seedlings or 1st year rosettes wherever possible as higher levels of control are achieved from each application, the smaller plants rot down more quickly (allowing livestock back into the area sooner), and less chemical is required minimising the effect on the environment. When treating Ragwort in grass intended for conservation (e.g. as hay / silage) autumn treatment is always the preferred timing, as spring treatment may not leave sufficient time for the dead Ragwort to rot away completely before the grass is cut and baled (DPIWE 2002). For further information on chemical control please see: Agriculture Victoria 2021; DPIRD 2021; DPI NSW 2019; and please see the Australian Pesticides and Veterinary Medicines Authority for chemical information http://www.apvma.gov.au .

Non-chemical control: Physical control: There is now evidence that humans may also be at serious risk from Ragwort poisoning through direct contact such as hand pulling without wearing protective gloves, or breathing in high quantities of pollen. For this reason it is essential that anyone handling Ragwort minimises skin contact and wears rubber gloves, and if in regular contact with flowering Ragwort, a dust mask with a pollen filter (DPIWE 2002; AgResource 2006).

Mechanical control: Digging, hand-pulling or mechanical pulling are all options, but all these methods allow potential re-growth from detached roots left in the soil. Second year plants must be removed from site before flowering as in addition to increasing risk of seed regeneration it also increases the risk to operator from alkaloid toxin exposure in the pollen as well as from the leaves and stems.

Competition and management: Maintenance of a dense vigorous pasture will reduce the opportunity for seedlings to establish and help to prevent the spread of Ragwort. This requires the judicious use of fertilisers and grazing management to avoid both overgrazing and under-grazing (DPIWE 2002).

Some farmers use grazing by sheep in an effort to control Ragwort as winter and spring grazing by sheep weakens plants. However sheep grazing will not eliminate Ragwort and the risk to the health of animals on heavily infested fields means that vets now discourage this technique (DPIWE 2002).

Ragwort control in poorly accessible areas may be best achieved by fencing off the area and allowing it to return to bush, or by the establishment of tree plantations. The control is achieved mainly by shading, with a contribution from plant competition (particularly in regenerating bush) and reduction in seed dispersal due to windbreak effects (McLaren & Faithfull 2004).

Biological Control: Several biological control programs are active in Tasmania and Victoria. The Ragwort Flea Beetle, Longitarsus flavicornis, which is a natural predator of Ragwort in Europe, was introduced to Tasmania in 1979. In 2000, field surveys indicated that the Ragwort Flea Beetle had spread over 90% of the total area of land infested by Ragwort. Within this area it is now starting to have a significant impact on Ragwort. Five insect species introduced to Victoria to control Ragwort, including the Ragwort Flea Beetle, have established (DPIWE 2002; McLaren et al. 1999; McLaren & Faithfull 2004).

Does it have a biological control agent?

YES

When does it grow? (lifecycle/growth calendar)

In the first year the seedling grows to form a rosette. In year two some plants mature and flower but others may be up to 5 years old before flowering and many die as rosettes without ever flowering. Generally seedlings appear in autumn (mostly) and spring and grow as rosettes until spring of year two, when more-upright foliage (the "cabbage" stage) is produced. Flowering stalks develop later in spring and in summer, with peak flowering from late January through to March. Odd plants may flower at any time. Mature seeds are formed a few weeks after the first appearance of flowers. Plants turn brown and die after seed set if undisturbed. Disturbance, such as cutting, grazing or ineffective chemical control stimulates regeneration from the crown and many plants develop multiple rosettes on a single crown. Seed can remain viable in the soil for at least eight years (Parsons & Cuthbertson 1992; Faithfull & McLaren 2004).

Where Is It Found?

Which states and territories is it found?

NSW, SA, TAS, VIC, WA

What areas within states and territories is it found?

Ragwort is most common and widespread in southern Victoria and Tasmania. Scattered infestations are also found throughout some other parts of Victoria and in south-eastern South Australia, south-eastern New South Wales and south-western Western Australia (Navie 2004).

In New South Wales it grows in isolated patches in south-eastern New South Wales.

In South Australia there are only two historical collection from 1954 from the Adelaide Hills in the Upper Sturt area (eFlora 2021).

In Tasmania Ragwort is widely distributed throughout the grazing areas of the state with exception of the Midlands where it occurs only as isolated plants and small patches. Its spread in this region has apparently been limited by low rainfall and sheep grazing. Infestations also occur on the shores of several lakes on the Central Plateau, and along roadsides in many areas. In Western Australia it is currently confined to one property, but pastures in the high rainfall districts (more than 750 mm) are at risk from this weed (DPIWE 2002; DSE 2004).

In Victoria, Ragwort is well established on the Mornington Peninsula and high rainfall areas of the Strzelecki, Otway and Dandenong ranges.

In WA there are only a few collections and it is currently confined to one property, but pastures in the high rainfall districts (more than 750 millimetres) are at risk from this weed.

Where does it originate?

Ragwort is native to Europe and Western Asia (DSE 2004).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?

NO

Where is it a declared weed?

NSW, SA, TAS, VIC, WA

Government weed strategies and lists – Weeds Australia

Is it on the National Alert List for Environmental Weeds?

NO

Government weed strategies and lists – Weeds Australia

Is it on the Agricultural Sleeper List?

NO

Government weed strategies and lists – Weeds Australia

Names And Taxonomy

Main scientific name

Senecio jacobaea

Other scientific names (synonyms)?

Does it have other known common name(s)?

Common Ragwort, St James Wort, Stagger Wort, Tansy Ragwort, Stinking Willie