Onopordum, or cottonthistle,[3] is a genus of plants in the tribe
Cardueae within the family
Asteraceae.[4] They are native to southern
Europe, northern
Africa, the
Canary Islands, the
Caucasus, and southwest and central
Asia. They grow on disturbed land, roadsides, arable land and pastures.[5]
They are
biennials (rarely short-lived
perennials) with branched, spinose winged
stems, growing 0.5–3 m tall. In the first season they form a basal rosette of gray-green
feltedleaves and rarely a few
flower heads. In the second season they grow rapidly to their final height, flowering extensively, and then die off after seed maturation.[6]
The leaves are dentate or shallowly lobed to compound with several pinnatifid or deeply cut leaflets, and strongly
spiny. The terminal flower head is typical for thistles, a semi-spherical to ovoid
capitulum with purple (seldom white or pink) disc florets. There are no ray florets. The receptacle is glabrous with dentate margins. The tube of the
corolla is slender, sac-shaped and symmetrical. The
anthers have awl-shaped outgrowths on the top. The capitula have several overlapping rows of leathery basal simple linear-lanceolate spines. These are smooth to slightly pubescent.
These plants propagate only by
seed. The seed heads mature in mid-summer, releasing their seeds. The
fruit is a glabrous
achene, 4–6 mm long and with 4-50 ribs. The pappus consists of many rows of simple, fine to minutely rough hairs, united in a circular base.[6]
In the
Greek island of
Crete a native species called agriagginara (αγριαγγινάρα) or koufoti (κουφωτοί) has its heads (flowers) and tender leaves eaten raw by the locals.[7]
Onopordum acanthium L. - Cotton thistle, Scotch thistle, Scotch common-thistle, heraldic thistle, woolly thistle - widespread across Europe and temperate Asia
Onopordum acaulon L. - Stemless thistle, horse thistle - France, Spain, Algeria, Morocco, Tunisia
Some species of Onopordum have been introduced as
ornamental plants in the temperate regions of
North America and
Australia, where they have become naturalised in the wild. In most of these countries, these thistles are considered noxious
weeds, especially in Australia where a biological control program has been set up (using the Rosette Crown
Weevil, Trichosirocalus briesei).[8] In North America, there are also Trichosirocalus control programs, but they have proved detrimental to native thistles.[9]
^Kleonikos G. Stavridakis , Κλεόνικος Γ. Σταυριδάκης (2006), Wild edible plants of Crete - Η Άγρια βρώσιμη χλωρίδα της Κρήτης, Rethymnon Crete,
ISBN978-960-631-179-6
^Briese, D. T.; Thomann, T.; Vitou, J. (2002), "Impact of the rosette crown weevil Trichosirocalus briesei on the growth and reproduction of Onopordum thistles", Journal of Applied Ecology, 39 (4): 688,
doi:10.1046/j.1365-2664.2002.00747.x
^Takahashi, Masaru; Louda, SM; Miller, TE; O'Brien, CW (2009), "Occurrence of Trichosirocalus horridus (Coleoptera: Curculionidae) on Native Cirsium altissimum Versus Exotic C. Vulgare in North American Tallgrass Prairie", Environmental Entomology, 38 (3): 731–40,
doi:10.1603/022.038.0325,
PMID19508782,
S2CID55487
Briese, D.T., Lane, D., Hyde-Wyatt, B.H., Crocker, J., Diver, R.G. (1990). Distribution of thistles of the genus Onopordum in Australia. Plant Protection Quarterly 5: 23–27.