Description
False Yellowhead (Dittrichia viscosa) is an erect to spreading, aromatic, soft-wooded perennialshrub, 1.5 m high and 1 m wide. Its leaves are 25-100 mm long x 8-30 mm wide ,elliptic (oval-shaped with the ends pinched together), alternate on the branches and have no stalk, and with serrate margins.
The yellow, daisy-like flowers are in heads 10-20 mm in diameter, surrounded by sticky leaf-like bracts (modified leaves). The seeds are about 2 mm long with about 15-25 bristles at the base.
For further information and assistance with identification of False Yellowhead contact the herbarium in your state or territory.
Distribution:
False Yellowhead is well established on the south coast of Western Australia, having spread from Albany to Mount Barker and Denmark, some 40 km to the north and west respectively. There are established remote populations at Walpole-Peaceful Bay, 60-80 km west of Albany, and at Mount Manypeaks, 60 km east of Albany. An isolated population has also been recorded on a train track at Yarloop some 350 km northwest of Albany and 125 km south of Perth. This infestation was possibly spread by seed carried by a train.
False Yellowhead has the potential to be a serious environmental weed, particularly in southwestern Western Australia and areas of similar climate in southern and eastern Australia.
Habit:
Shrub,
Key points:
- False Yellowhead (Dittrichia viscosa) produces large numbers of seeds and is spreading rapidly along roadsides and walking trails in southwestern Western Australia.
- It favours disturbed habitat, particularly after fires. Preventing the further spread of False Yellowhead is cheaper and easier than all other control options.
- Control of established infestations can be achieved by physical and chemical means, and should be conducted before flowering occurs in summer.
- If you see this weed, contact your state or territory weed management agency or local council. Do not attempt control without their assistance
How it spreads:
False Yellowhead spreads by seed. Seed dispersal is aided by the pappus, an arrangement of bristles at the top of the seed, which catches the wind or can assist flotation. Seed can also be spread during soil movement (eg in road making or road grading) or when attached to machinery.
Where it grows:
False Yellowhead usually prefers, but is not restricted to, high rainfall areas. It can be found on both clay and sandy soils. In southwestern Western Australia it is found in areas of medium to high rainfall (i.e. where rainfall exceeds 400 mm per year). It is more reliant on moisture than the closely related Stinkwort (Dittrichia graveolens), which is a weed of grazing land and roadsides of much of southern Australia. In southwestern Western Australia nearly all records of False Yellowhead are from highly disturbed sites: road verges (20 records), firebreaks (one record) and walking trails (two records). Of the three records from bushland, all are from disturbed sites in swamps (Lake Seppings, Mount Manypeaks, and a creek line and swamp at Emu Point).
Flower colour:
Yellow
Distribution map:
Impacts:
False Yellowhead is on the Alert List for Environmental Weeds, a list of 28 non-native plants that threaten biodiversity and cause other environmental damage. Although only in the early stages of establishment, these weeds have the potential to seriously degrade Australia’s ecosystems.
False Yellowhead, like Stinkwort (D. graveolens), can cause health problems in humans and animals. The oil on the leaves and stems causes contact dermatitis, resulting in itching and blistering skin. Stock that eat the flower heads of Stinkwort can develop enteritis (inflammation of the small intestine) because the pappus irritates and punctures the lining of the small intestine, eventually leading to pulpy kidney disease and sudden death if untreated. It is thought that False Yellowhead would have similar impacts on grazing animals.
Infestations of False Yellowhead would detract from the aesthetic and natural values of bushland and could reduce its tourism appeal. The costs of management (e.g. clearing from railway lines or walking trails) would also be significant.
Origin:
False Yellowhead is native to southern Europe (including France, Portugal, Spain, Greece, Albania, Bulgaria and Italy) through to Turkey and the Middle East (Israel, Jordan, Lebanon, Syria and Cyprus).
It is also found in northern Africa (Algeria, Egypt, Libya, Morocco and Tunisia).
History:
Originally from the Mediterranean region, it is not clear how False Yellowhead was introduced to Australia but it may be a garden escape. It was first recorded in Albany in 1955 and has since spread throughout southern Western Australia. It is occasionally found in swamps but mainly occurs in highly disturbed areas such as roadsides, railway lines, fire breaks and walking trails.
