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]
Cotton thistle (Onopordum acanthium) from Thomé Flora von Deutschland, Österreich und der Schweiz 1885
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 Onopordum acanthium - habit - 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, Bibcode:2002JApEc..39..688B, 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.
