Onopordum is the Latin name for thistles and is derived from the Greek onus meaning donkey and porde meaning flatulence because it was believed that donkeys farted more after eating these plants.
Illyricum is from its ancient country of origin Illyria near present day Albania and Dalmatia.
Illyrian Thistle - refers to the ancient country of origin, Illyria.
Summary:
A spiny, woolly, tall annual to biennial thistle with single, spiny, red to purple flowers on the ends of stems.
Description:
Cotyledons:
Two.
Leaves:
Form a rosette up to 600 mm wide.
Petiole - Merging petiole on the rosette leave to none on the stem leaves.
Blade - Whitish grey, densely woolly, deep lobes with large teeth, edges spiny. Rosette leaves up to 300 mm long.
Stem leaves - Smaller and held at right angles to the stem. Leaves continue down the stem as wings.
Stems:
Erect, up to 2500 mm tall, whitish grey. Covered in white woolly hairs. Branched near the top. Leaves continue down the stem as large, spiny wings.
Flower head:
Single at the ends of stems, purple, globular, up to 80 mm diameter (including bracts). Many spiny bracts.
Flowers:
Many reddish purple florets sticking out of the top of the flower head.
Bracts - large, more than 3 mm wide, oval to lance shaped, purple on one or both sides, a few webbed hairs, tiny teeth or rough on edges, with a sharp yellow spine. All bracts bent back.
Florets - Tubular, many, red-purple, protrude from the head.
Ovary - Receptacle is fleshy with no scales, honeycombed with pits with jagged edges.
'Petals' - Purple.
Stamens -
Anthers -
Fruit:
Light brown to grey, egg shaped, crosswise wrinkled with tiny pits, flattened achene, 5-7 mm long. Pappus of many bristles, 8-10 mm long, joined in a ring at the base and falls off easily
Seeds:
Enclosed in the fruit.
Roots:
Long, thick taproot.
Key Characters:
Bracts purplish, all reflexed, more than 3 mm wide, slightly webby or minutely 1-seriate scabrid(rough) on the margins. Stem leaves at right angles to stem.
Biology:
Life cycle:
Annual or biennial Seed germinates at any time with a flush in autumn. A rosette of leaves is produced over winter. Some develop stems and flower in spring. Others remain vegetative and flower in the following spring. Plants die in summer after flowering.
Physiology:
Reproduction:
By seed.
Flowering times:
Spring.
Seed Biology and Germination:
Produces dormant seed.
Vegetative Propagules:
Hybrids:
It hybridises with Scotch Thistles and many infestations are mixtures of the two thistles plus the hybrids.
Allelopathy:
Population Dynamics and Dispersal:
Spread by seed in the wind, water, wool, agricultural produce and machinery.
Origin and History:
South Western Europe. Mediterranean. Asia minor.
Known in Victoria in the 1930's and probably present 60 years earlier.
Distribution:
ACT, NSW, SA, VIC.
About 1000 hectares infested in Victoria.
In NSW it occurs in combination with Scotch Thistle and infests around 200,000 hectares.
Habitats:
Climate:
Sub humid temperate regions.
Most abundant in areas with an annual rainfall of 600-800 mm.
Soil:
Most abundant on soils of moderate to high fertility and rocky hillsides.
Plant Associations:
Often grows in association with the closely related Scotch Thistle (O. acanthium) and intermediate forms exist.
Significance:
Beneficial:
Detrimental:
Weed of pastures, roadsides and disturbed areas.
Contaminates wool.
Not grazed because of it spiny nature.
Restrict stock and human movement when it forms dense stands.
Toxicity:
Not recorded as toxic.
Legislation:
Noxious weed of ACT, NSW, Tas and Vic.
Management and Control:
Seed is spread by wind, water, attachment to wool, in produce and by machinery. Control of seed set is important to prevent spread. Cultivation and young plants can be controlled by cultivation. Isolated plants can be removed mechanically provided the bulk of the taproot is removed. Perennial grasses compete effectively and reduce seedling establishment. Goats and to a lesser extent cattle graze on the seed heads and reduce infestations. Sheep avoid eating it. Hormone herbicides are effective on young plants before the stem emerges. Glyphosate is effective on young and older plants. Wick applicators allow more selective application of glyphosate in pasture situations.
Thresholds:
Eradication strategies:
Prevent seed set. Manually remove isolated plants. Spray heavier infestations with herbicides and establish perennial pastures. MCPA and 2,4-D are effective on seedlings but not on mature plants. Dicamba and glyphosate are more effective on larger plants. Graze with goats or cattle rather than sheep.
Herbicide resistance:
Biological Control:
Related plants:
Scotch Thistle (Onopordum acanthium) is very similar but has green, narrower (<3 mm) bracts and only the outer bracts are bent back on the flower head.
Stemless Thistle (Onopordum acaulon) has no stem.
Onopordum tauricum is only found in Victoria, has sparse hairs and is greener.
Plants of similar appearance:
Spear Thistle (Cirsium vulgare) is similar but has a different leaf shape.
References:
Auld, B.A. and Medd R.W. (1992). Weeds. An illustrated botanical guide to the weeds of Australia. (Inkata Press, Melbourne). P108.
Burbidge, N.T. and Gray, M. (1970). Flora of the Australian Capital Territory. (Australian National University Press, Canberra). P392.
Lamp, C. and Collet, F. (1990). A Field Guide to Weeds in Australia. (Inkata Press, Melbourne).
Lazarides, M. and Hince, B. (1993). CSIRO handbook of economic plants of Australia. (CSIRO, Melbourne). #902.3.
Parsons, W.T. and Cuthbertson, E.G. (1992). Noxious weeds of Australia. (Inkata Press, Melbourne). p221-222.
Acknowledgments:
Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.