Dittrichia viscosa (L.) Greuter
Synonyms - Inula viscosa
Dittrichia celebrates the German botanist M. Dittrich.
Viscosa is from the Latin word viscosus meaning sticky to touch.
False Yellowhead because it resmembles the related British Yellowhead (Inula Britannica).
Other Names:Camphour Inula
Summary:False Yellowhead (Dittrichia viscosa) is a bushy, woody perennial herb or shrub to 1.5 m high with spreading branches. The toothed leaves are sticky and often have an unpleasant smell when crushed. Secreted oil makes the plant sticky to touch. The abundant, bright yellow daisy flower heads are 8-20 mm across and have radiating petal-like florets. The tiny fruits are topped by a ring of fine bristles.
Native to the Mediterranean region, this species is now spreading along roadsides between Walpole and Jerramungup, particularly in swampy areas.
It flowers from February to May.
Two. Oval. Tip round. Base tapered. Hairless.
First leaves:Club shaped. Tip round. Base tapered. Hairs on upper surface. No petiole.
Leaves:Mostly alternate. Forms a basal rosette to 200 mm wide when young.
Stipules - None.
Petiole - None.
Blade - Narrowly elliptic to elliptic, 25-100 mm long x 5-30 mm wide, soft. Veins usually indented on the upper surface. Edges distinctly toothed, hairy and curved or rolled inwards. Tip pointed. Base tapered to almost clasping.
Stem leaves - Entire, almost stem clasping, up to 60 mm long. Taper to a point at the tip.
Stems:Spreading, bushy, woody, rigid, oily to touch, 200-1500 mm tall. Often unpleasantly aromatic when crushed.
Dense glandular hairs and broad based hairs with thread like tips?.
Flower head:Many, bell shaped, 10-20 mm long x 10-25 mm wide, in long loose, leafy, pyramid like panicles surrounded by sticky bracts. On the ends of branches and on very short stalks in the leaf axils.
Flowers:Yellow daisy-like flowers about 20 mm diameter with 10-12 "petals".
Bracts - 3 or 4 rows surround the flower head. Outer ones are leafy, green, narrow, sticky, and parallel sided to triangular, 3-9 mm long x 3 mm wide, many glandular hairs and a few long hairs, tip has tiny hairs. Inner bracts are longer with pale edges.
Florets - Ray florets, 10-12, outer, female with a ligule 6-12 mm long.
Disk florets - Bisexual, yellow, tubular, 4 or 5 lobed.
Ovary - Receptacle is flat or slightly convex, without bracts?.
'Petals' - 10-12, yellow, 6-12 mm long.
Anthers - Tailed at the base.
Fruit:Achene. Light brown, almost cylindrical, 2 mm long, downy with fine hairs. Narrowed to a neck at the top, then expanded into a small cup supporting the pappus.
Pappus of about 15-20 bristles, 3-4 mm long. Looks simple to the naked eye, but are fused together at their base and are barbed.
Seeds:Enclosed in the fruit.
Roots:Strong taproot with many laterals.
Key Characters:Yellow daisy-like flowers 8-20 mm wide. Pappus of 15-20 barbed bristles shed in a ring.
Perennial. Germinates and grows forming small, slow growing rosettes until warm weather occurs. Flowering mainly in summer and autumn.
Flowering times: February to May
Seed Biology and Germination:Seeds are short lived and probably don't survive more than 3 years.
Expected to be allelopathic.
Population Dynamics and Dispersal:Fluffy seed dispersed by wind, water, stock and machinery.
Seedlings are very sensitive to competition and usually only establish in relatively bare areas.
Origin and History:Mediterranean.
In WA it was first recorded in Albany in 1980 and has spread approximately 160 km to Jerramungup in the east, Peaceful Bay in the west and Mount Barker to the north. It has also been recorded at Bunbury, Perth and the Murchison.
Courtesy Australia's Virtual Herbarium.
Warm temperate and sub tropical areas. Areas with an annual rainfall of 300-800 mm.
Soil:Sandy, peaty or gravelly soils, swampy areas, depressions and roadside drains.
Taints milk and meat but not usually grazed by stock.
Weed of roadsides, railways and disturbed areas.
Toxicity:Reported to be toxic and causes contact dermatitis (Hussey et al., 1997).
Can cause severe dermatitis in humans especially if handled when in flower. Some people are allergic to the aromatic oils.
Management and Control:
Low rates of clopyralid (Lontrel®) will probably provide good levels of selective control in many bushland areas.
Small areas can be mechanically removed. Plants in flower must be burnt as seed will develop from the nutrient reserves in the stem if left on the ground. Mowing reduces seeding and can eventually provide control if done regularly and as close to the ground as possible.
Cultivation of larger plants is only effective if done before flowering during dry weather. Regrowth often occurs if adequate soil moisture is present.
Spray plants with a mixture of 100 mL Access® in 10 L of diesel any time they are actively growing from spring to autumn. This treatment will kill most broad-leaved species it contacts, however some selectivity can be achieved by only spraying the deep centre of each bush. In sensitive areas use 200 g/ha Lontrel®750 plus wetting agent or 4 g Lontrel®750 plus 25 mL Pulse® in 10 L water as an overall spray in early summer.
False Yellowhead probably has allelopathic chemicals which reduce the growth of companion plants.
Infestations up-wind or up-stream may need to be controlled to prevent re-infestation.
It is relatively tolerant to glyphosate, metsulfuron and hormone herbicides.
Herbicide resistance:Relatively tolerant to glyphosate and hormone herbicides.
Biological Control:Related plants:
Stinkwort (Dittrichia graveolens) has much smaller yellow flowers 4-7 mm wide and 25-30 pappus bristles.
Plants of similar appearance:Fleabanes (Conyza species) are not sticky to touch and is not aromatic.
Kochia (Bassia scoparia) is larger and has three parallel veins on the leaf and is not aromatic or sticky.
Tumbleweed (Amaranthus albus) is not aromatic or sticky and tends to have whitish stems.
References:Bodkin, F. (1986). Encyclopaedia Botanica. (Angus and Robertson, Australia).
Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney).
Hussey, B.M.J., Keighery, G.J., Cousens, R.D., Dodd, J. and Lloyd, S.G. (1997). Western Weeds. A guide to the weeds of Western Australia. (Plant Protection Society of Western Australia, Perth, Western Australia). P96. Photo.
Lazarides, M. and Cowley, K. and Hohnen, P. (1997). CSIRO handbook of Australian Weeds. (CSIRO, Melbourne). #358.2
McBarron, E.J. (1983). Poisonous plants. (Inkata Press, Melbourne).
Moore, J.H. and Wheeler, J.R. (2002). Southern Weeds and their Control. P144-145. Photos.
Paczkowska, G. and Chapman, A. (2000). The Western Australia flora: a descriptive catalogue. (Wildflower Society of Western Australia (Inc), the Western Australian Herbarium, CALM and the Botanic Gardens & Parks Authority). P161.
Randall, J.M. and Marinelli, J. (1996) Invasive Plants. (Brooklyn Botanic Gardens Inc. Brooklyn). P. Photo.
Wheeler, Judy, Marchant, Neville and Lewington, Margaret. (2002). Flora of the South West: Bunbury - Augusta - Denmark. (Western Australian Herbarium, Bentley, Western Australia). P505. Diagrams.
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