Quick Facts

Quick facts

• Originally from the Mediterranean region Stinkwort (Dittrichia graveolens) is a summer-growing annual, strong-smelling, sticky, much-branched, annual herb, that grows to under 1m high, with many cluster of yellow flowers, producing many seeds.
• Spread by seed only, conical, rounded to pyramidal in shape, with a strong camphor or oil-kerosene-like odour, can cause contact dermatitis.
• Invades disturbed areas, including roadsides, abandoned sites, tracks and open and degraded native vegetation.
• An agricultural weed in southern Australia normally avoided by grazing by stock or only eaten when young when little else is available.
• The seeds (actually one-seeded fruits) are spread by wind and water, as attachments on machinery, vehicles, wool, skins, bags and clothing, and as contaminants of sand and gravel.
• A variety of measures can be used to control Stinkwort including hand-pulling (wearing gloves), burning, cultivation, slashing,  herbicide, and grazing by sheep when the plants are young.
• Gloves should be worn when handling the plant as some people are quite sensitive and it may take several months for the dermatitis to clear.

What Does It Look Like?

What is it?

Stinkwort (Dittrichia graveolens) is a more or less conical, sticky, erect, multi-branched, oil-kerosene to camphor-scented annual herb growing to 1.2 m (more usually 30–60 cm) high, all leaves and stems with simple and glandular hairs, and glands. The first leaves produced are arranged in a basal rosette, 20–70 mm long, 1–8 mm wide, with finely toothed margins or entire (no teeth), lanceolate (lance-shaped, about 4 times as long as broad, broadest in the lower half and tapering to the tip) to oblanceolate (lance-shaped about 4 times as long as broad, broadest point at the apex). Rosette leaves are pubescent (downy; covered with short, soft, erect hairs) with simple and glandular hairs, these leaves soon wither when the main stem is produced. The stem leaves are smaller than rosette leaves, being narrow, mostly 10–40 mm long and 1–3 mm wide, linear (very narrow in relation to its length, with the sides mostly parallel ) to narrow-oblanceolate, and covered in hairs and small round glands that exude sticky, strong-smelling oil.

The flower heads are individual with yellow daisy-like flowers borne on short stalks 0–5 mm long in the leaf axils (in junction between leaf and stem). Flower heads are borne singly along leafy branches that are covered in similar and glandular hairs and glands similar to those on the leaves. Individual flower heads are 5-7 mm wide and are composed of tubular florets (flowers with strap-like petals) 4–7 mm long. Clusters of flowers (flower heads) are surrounded by a group of bracts (leaf-like structures), all 2–7 mm long. The outer bracts are glandular (have glands), hairy with and without glands, particularly on margins. The  inner bracts more or less glabrous (smooth with out hats). After flowering, individual flower heads produce several hairy, one-seeded fruits.

The fruits or 'seeds' (cypselas) are hairy and occasionally glandular, 1.5–2 mm long, 7–8 mm wide, each crowned by many ( 25–30) fine soft plumose (like a feather; with fine hairs branching from a main axis) hairs (the pappus), 3–4 mm long (Brown 1992; Jeanes 1999; Parsons & Cuthbertson 2001).

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

Flower colour

Yellow

Growth form (weed type/habit)

Herb

Where it currently grows? Preferred habitat

Stinkwort (Dittrichia graveolens) is one of the most widespread weeds in the southern half of Australia, found in the cool to warm temperate areas. Climatically, Stinkwort is adapted to a temperate, ‘Mediterranean-type’ climate with an annual rainfall of 300–800 mm, falling predominantly in winter. While it can persist in warmer, sub-humid areas, and arid areas, these climate zone appears very marginal, outside if preferred ecological zone (State of Queensland, 2016).

It grows in virtually any open, disturbed sites, such as overgrazed pastures, roadsides and vacant lots, mainly on sandy or otherwise light-textured soils. It typically colonises bare sites where there is poor competition from other plants (State of Queensland, 2016). Also is found on railway reserves, river flats, grazing land,  with a preference for depressions (Jeanes 1999; Parsons & Cuthbertson 2001; National Herbarium of Victoria 2007).

Are there similar species?

Stinkwort is superficially similar to other widespread weedy annual daisies such as:

• Aster-weed (Aster subulatus) and
• Fleabanes (Conyza spp.)

The strong-smelling, glandular leaves, stems and flowering branches should readily distinguish it (Reid 2008 pers. comm.).

Why Is It A Weed?

What are its impacts?

Stinkwort (Dittrichia graveolens) is a weed of pastures, crops, lucerne, fallows, roadsides, railways, slightly saline areas, summer moist areas, watercourses, summer crops and irrigated and disturbed areas. Historically, the species was mainly a weed of agricultural areas, but it is also regarded as an environmental weed in some areas invading conservation areas. Stinkwort exudes a strong-smelling oil from glands on most parts of the plant. This causes allergic contact dermatitis in some people.

Agriculture: Although reported as toxic and poisonous to livestock, little evidence exists that it is toxic, although oxalate poisoning has been reported when it is grazed, and fishermen in southern Italy reportedly use the macerated leaves to stun fish. Grazing animals appear to find Stinkwort fairly unpalatable, eating the plant only when it is very young, when little else is available. The oil also taints meat and milk of animals forced to graze the plant (Mitchell & Rook 1979; Parsons & Cuthbertson 2001; Flora of North America undated). Discolours wool but it comes out during scouring.

Native ecosystems: While Stinkwort is mainly a weed of agricultural land and highly disturbed sites, it is also rated a potential threat to dry coastal vegetation, mallee shrubland, lowland grassland and grassy woodland, and dry sclerophyll forest and woodland (Carr et al. 1992). It primarily occurs on land subjected to grazing or other disturbance (e.g. roadsides), but also grows along waterways (i.e. in riparian zones), in wetlands and in coastal habitats (Queensland Government 2016).

Urban areas: A weed of roadsides and waste place especially in agricultural and regional areas.

How does it spread?

Stinkwort (Dittrichia graveolens) spreads by seed only, as it is an annual (a plant that completes its life-cycle and dies within one year), it is totally reliant on its one-seeded fruits for reproduction and dispersal. Seeds survive in the soil (soil seedbank) for up to 3 years. The pappus hairs that crown the fruits facilitate dispersal by wind and water. The fruits also to attach and disperse on machinery, vehicles, wool, skins, bags and clothing. Stinkwort fruits are also dispersed as a contaminant of sand and gravel used for road making (Parsons & Cuthbertson 2001).

What is its history in Australia?

Stinkwort was probably introduced to Australia in contaminated wheat imported to South Australia from Germany in the 1860s. By 1890 it was recognised as the worst weed of cereal crops in that state and had also spread to New South Wales, Victoria and Western Australia, becoming one of the most widespread weeds in Australia (Parsons & Cuthbertson 2001).

How To Manage It?

Best practice management

Stinkwort (Dittrichia graveolens) can be controlled by physical and mechanical means, and herbicides. Treatment should be carried on young plants early in the season when the plant in rosette form, before flowering. Older plants with flowers and seeds are tolerant to herbicides, and plants sprayed when in flower  may set seed and regrow. Plants treated by mechanical means (slashing and mowing) will also regrow and will need follow-up. In addition, slashed or mown cut dead flowering material may develop viable seed and should be removed from sites. Timing it important to kill or manage plants to prevent seed set, with seeds viable for only three years. Reducing the soil seed bank is the goal to reduce or eradicate Stinkwort from an area. Control programs should also address the reasons why Stinkwort has become a weed in a particular area. These include; over-grazed; bare areas;  poor and degraded soil with nutritional deficiencies; soil salinity. Better management and introducing more suitable cover species to consume summer moisture may help.

Chemical control: Stinkwort can also be sprayed with herbicide, particularly in the young growth stages (Parsons & Cuthbertson 2001). Older plants are relatively tolerant of herbicides including glyphosate, metsulfuron and hormone herbicides. Please see the Australian Pesticides and Veterinary Medicines Authority for chemical information http://www.apvma.gov.au 

Non-chemical control: Physical control: Isolated plants or small patches of Stinkwort can be hand-pulled (wearing gloves) before they flower. Plants in flower need to be put in heaps and burned to prevent continued growth and seed production.

Does it have a biological control agent?

NO

When does it grow? (lifecycle/growth calendar)

The seeds of Stinkwort (Dittrichia graveolens) germinate in spring and form small leaf rosettes which grow slowly until early summer. Warmer weather stimulates rapid growth of the rosette, followed by the main stem, and eventually the mature plant. Flowers are produced mainly between March and May. The plants are killed in winter with the onset of cooler temperatures and frosts (Parsons & Cuthbertson 2001).

Where Is It Found?

Which states and territories is it found?

Found in all Australian states and territories.

What areas within states and territories is it found?

Stinkwort (Dittrichia graveolens) is widespread and common in New South Wales, Victoria, South Australia, Tasmania, and southwest Western Australia. There are also limited patches in the Australian Capital Territory and southeast Queensland, where It is only found in cooler south-east areas particularly near Stanthorpe, and there a single collection from the Northern Territory where is it listed as questionably naturalised (Parsons & Cuthbertson 2001; APC 2021; AVH 2021).

Where does it originate?

Stinkwort is native to the Mediterranean region (Jeanes 1999).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?

NO

Where is it a declared weed?

VIC

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

Dittrichia graveolens

Other scientific names (synonyms)?

Does it have other known common name(s)?

Stinkweed, Stink-weed, Camphor Inula, Khaki Weed, Cape Khaki Weed