stinkweed

Dittrichia graveolens
Stinkweed
Stinkweed
Stinkweed
Stinkweed flower detail
Stinkweed
Stinkweed
Herb
Basal
Simple
Yellow
Green

A short-lived herbaceous plant with upright and much-branched stems growing up to 1 m tall. It forms a basal rosette of leaves at first. Its long and narrow leaves are stalkless with finely toothed or entire margins. Its stems, leaves and young flower-heads are covered in sticky hairs. Its small yellow flower-heads (7-10 mm long) have several small 'petals'. Its small 'seeds' (about 2 mm long) are topped with a ring of hairs or bristles (3-4 mm long). Plants give off a strong, unpleasant odour when crushed.

Common names 
Also known as: Camphor inula, Cape khakiweed, stinking fleabane, stinkwort,
Family 
Asteraceae
Deciduous 
No
Flowering time 
Summer-Autumn
Native/Exotic 
Exotic
Origin 
This species is native to the southern Europe, northern Africa, western Asia and Pakistan.
Notifiable 
No
Council declaration 
SIL – Special Investigation List
Known distribution 

This species is widely naturalised in the semi-arid and temperate regions of southern Australia. It is most common in Victoria, south-eastern South Australia, south-western and western Western Australia and the sub-coastal districts of southern and central New South Wales. Less common in other parts of New South Wales and South Australia and present in Tasmania and south-eastern Queensland.

Habitat 

A weed of pastures, roadsides, crops, fallows, disturbed sites and waste areas.

Habit 

A short-lived (i.e. annual) herbaceous plant with upright (erect) and much-branched stems usually growing 30-60 cm tall, but sometimes reaching up to 1 m in height.

Impact and control methods 

Stinkwort (Dittrichia graveolens) is mainly a weed of agricultural areas and habitation in southern Australia, but it is also regarded as an environmental weed in some states. It primarily occurs on land that is subjected to grazing or other disturbances (e.g. roadsides), but also grows along waterways (i.e. in riparian zones), in wetlands and in coastal habitats. However, stinkwort (Dittrichia graveolens) has invaded numerous conservation areas in Victoria, South Australia, Western Australia and New South Wales.

This species has a very limited distribution in south-eastern Queensland, and is not regarded as an environmental weed in the region.

Stem and leaves 

The much-branched stems are rigid, slightly woody towards the base of the plant, and covered with small sticky (i.e. glandular) hairs.

The leaves are elongated (i.e. lanceolate) or very narrow (i.e. linear) in shape and usually stalkless (i.e. sessile). These leaves are initially borne in a basal rosette, and then alternately arranged along the stems. Rosette leaves are larger (up to 10 cm long) and have finely toothed (i.e. denticulate) margins, while those along the stems are smaller (1-5 cm long and 1-6 mm wide) and often have entire margins. The leaves are covered in hairs similar to those found on the stems (i.e. they are galndular pubescent).

Flowers and fruits 

The small yellow flower-heads (i.e. capitula) are borne singly at the tips of the branches or in the upper leaf forks (i.e. axils), but are formed into large leafy clusters (i.e. panicles). These flower-heads (7-10 mm long and 3-10 mm across) are stalkless (i.e. sessile) or borne on short stalks (i.e. peduncles) up to 5 mm long. They have several (6-12) small yellow 'petals' (i.e. ray florets) 4-7 mm long and several tiny flowers (i.e. tubular or disc florets) in the centre. The flower-heads are surrounded by two rows of narrow green bracts that are covered in sticky (i.e. glandular) hairs. Flowering occurs from late summer through to early winter, but is most abundant during autumn.

The 'seeds' (i.e. achenes or cypselae) are light brown in colour, oval (i.e. ellipsoid) in shape, and about 2 mm long. The are covered with fine hairs and topped with a ring (i.e. pappus) of numerous larger hairs or bristles (3-4 mm long).

Reproduction and dispersal 

This species reproduces by seeds that are largely dispersed by wind and water. These seeds may also be spread as a contaminant of agricultural produce or by becoming attached to other objects (i.e. animals, vehicles and clothing).

Similar species 

Stinkwort (Dittrichia graveolens) is relatively similar to the fleabanes (Conyza spp.) and telegraph weed (Heterotheca grandiflora ). These species can be distinguished by the following differences:

■stinkwort (Dittrichia graveolens) has younger stems, leaves and flower-head bracts that are covered in sticky (i.e. glandular) hairs. Its relatively small flower-heads (3-10 mm across) have several small yellow 'petals' (i.e. ray florets) and its lower leaves are mostly narrow and elongated (i.e. lanceolate) in shape with almost entire margins.

■the fleabanes (Conyza spp.) have stems, leaves and flower-heads that are not covered in sticky (i.e. glandular) hairs. Their relatively small flower-heads (usually less than 10 mm across when in flower) do not have any obvious 'petals' (i.e. ray florets), and their lower leaves are generally elongated in shape (i.e. narrowly elliptic or lanceolate) with toothed or slightly lobed margins.

■telegraph weed (Heterotheca grandiflora ) has stems, leaves and flower-head bracts that are sometimes covered in sticky (i.e. glandular) hairs. Its relatively large flower-heads (15-22 mm across) have many yellow 'petals' (i.e. ray florets) and its lower leaves are relatively broad (i.e. elliptic or narrowly elliptic) with toothed margins.