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.
Growth form (weed type/habit)
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.).