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Scientific Name
Synonyms
Family
Common Names
Origin
Naturalised Distribution
Habitat
Habit
Distinguishing Features
Stems and Leaves
Flowers and Fruit
Reproduction and Dispersal
Environmental Impact
Legislation
Management
Similar Species
Print Fact Sheet
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Click on images to enlarge

large infestation (Photo: Sheldon Navie)

habit (Photo: Steve Adkins)

habit (Photo: Trevor James)

elongated and deeply-divided lower leaf (Photo: Trevor James)

stem and upper leaf (Photo: Sheldon Navie)

close-up of deeply-divided upper leaf (Photo: Trevor James)

cluster of numerous flower-heads (Photo: Sheldon Navie)

close-up of young flower-heads (Photo: Trevor James)

seedling (Photo: Trevor James)

young plants (Photo: Trevor James)

Senecio jacobaea

Scientific Name

Senecio jacobaea L.

Synonyms

Jacobaea vulgaris Gaertn.

Family

Asteraceae (Queensland, New South Wales, the ACT, Victoria, Tasmania, Western Australia and the Northern Territory)
Compositae (South Australia)

Common Names

common ragwort, hysterical weed, ragwort, stagger wort, staggerwort, tansy butterweed, tansy ragwort, stinking willie, stinking willy, St James' wort, yellow ragwort

Origin

Native to north-western Africa (i.e. Algeria, Morocco and Tunisia), Europe and western and central Asia (i.e. Lebanon, Syria, Armenia, Azerbaijan, Georgia, Russia, Kazakhstan, Tajikistan, Uzbekistan and Mongolia).

Naturalised Distribution

Widely naturalised in southern Australia (i.e. on the southern and central tablelands regions of New South Wales, in Victoria and Tasmania, in south-eastern South Australia and in south-western Western Australia).

Habitat

A weed of pastures, open woodlands, disturbed sites, waterways, swamps, lake margins, and sometimes also crops, in wetter temperate regions.

Habit

An upright (i.e. erect) and relatively long-lived (i.e. biennial or perennial) herbaceous plant usually growing 45-120 cm tall, but occasionally reaching up to 1.8 m in height. This species forms a basal rosette of leaves during the early stages of growth.

Distinguishing Features

Stems and Leaves

One or more upright (i.e. erect) stems arise from a long-lived (i.e. biennial or perennial) rootstock. These stems are much-branched towards the top of the plant and are ribbed or furrowed. They may be initially sparsely covered in cobweb-like hairs and are often reddish or purplish in colour towards the base of the plant.

All leaves are dark green and hairless (i.e. glabrous) above and somewhat paler underneath (i.e. discolorous) with a covering of downy or cobwebby hairs (i.e. pubescent). Rosette leaves are relatively large (up to 35 cm long), with distinct stalk-like (i.e. petiolate) bases (10-30 mm long) and deeply divided margins. Stem (i.e. cauline) leaves are smaller (up to 15 cm long) and often stalkless (i.e. sessile) or stem-clasping.

Flowers and Fruit

The bright yellow flower-heads (i.e. capitula) are borne in dense clusters at the tops of the branches. These flower-heads (20-25 mm across) have several (12-15) elongated 'petals' (i.e. ray florets) that are 6-10 mm long and about 1 mm wide. They also have numerous small 'disc' or 'tubular' florets in the centre and are surrounded by several (about 13) small greenish bracts (5-6 mm long) that have black or brown coloured tips. Flowering occurs during summer and early autumn.

The seeds (i.e. achenes) are brown in colour (1-3 mm long) and topped (at least initially) with a ring (i.e. pappus) of fine whitish hairs (4-6 mm long). Some of the seeds (those produced by the ray florets) are smooth in texture and hairless (i.e. glabrous), while the majority (those produced by the tubular florets) are covered in fine hairs or bristles.

Reproduction and Dispersal

Reproduction occurs via seed and from pieces of the long-lived crowns.

Most dispersal of this species is thought to be a result of seeds being spread by wind, water, animals, vehicles, humans and in contaminated agricultural produce. Spread may also occur when root and crown segments are broken off and moved to new areas by cultivation equipment and other machinery.

Environmental Impact

Ragwort (Senecio jacobaea) is regarded as an environmental weed in Victoria and Tasmania, and was recently listed as a priority environmental weed in three Natural Resource Management regions.

Legislation

This species is declared under legislation in the following states and territories:

Management

For information on the management of this species see the following resources:

Similar Species

Ragwort (Senecio jacobaea ) is similar to several introduced species including common groundsel (Senecio vulgaris), fireweed (Senecio madagascariensis) and African daisy (Senecio pterophorus). These species can be differentiated by the following differences:

Ragwort (Senecio jacobaea) is also similar to several native Senecio species, which cannot all be mentioned here.