Onopordum


[Image:Illustration Onopordum acanthium0.jpg|thumb|Cotton thistle (Onopordum acanthium) from Thomé Flora von Deutschland, Österreich und der Schweiz 1885]
Onopordum, or cottonthistle, is a genus of plants in the tribe Cardueae within the family Asteraceae. 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.
They are biennials with branched, spinose winged stems, growing 0.5–3 m tall. In the first season they form a basal rosette of gray-green felted leaves 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.
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 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.
Onopordum species are used as food plants by the larvae of some Lepidoptera species including Coleophora onopordiella.
In the Greek island of Crete a native species called agriagginara or koufoti has its heads and tender leaves eaten raw by the locals.
; SpeciesOnopordum acanthium L. - Cotton thistle, Scotch thistle, Scotch common-thistle, heraldic thistle, woolly thistle [Image:Onopordum bracteatum1.jpg|thumb|right|Onopordum acanthium - habit] - widespread across Europe and temperate AsiaOnopordum acaulon L. - Stemless thistle, horse thistle - France, Spain, Algeria, Morocco, TunisiaOnopordum alexandrinum Boiss. - Egypt, Palestine, Lebanon, Syria, Israel, JordanOnopordum algeriense Pomel - AlgeriaOnopordum ambiguum Fresen. - Egypt, Palestine, Lebanon, Syria, Israel, JordanOnopordum anatolicum Eig. - TurkeyOnopordum arenarium M.Hossain & M.A.A.Al-Sarraf - Algeria, Morocco, Tunisia, LibyaOnopordum armenum Grossh. - Caucasus, Iran, TurkeyOnopordum blancheanum Danin - Israel, Palestine, Jordan, Syria, LebanonOnopordum boissierianum Raab-Straube & Greuter - TurkeyOnopordum bracteatum Boiss. & Heldr. - Greece, Turkey, CyprusOnopordum canum Eig - Iran, Jordan, Israel, TurkeyOnopordum carduchorum Bornm. & Beauverd - Lebanon, Syria, Turkey, IranOnopordum carduelium Bolle - Canary IslandsOnopordum carduiforme Boiss. - Egypt, Palestine, Lebanon, Syria, Israel, JordanOnopordum carmanicum Bornm. - IranOnopordum caulescens d'Urv. - GreeceOnopordum cinereum Grossh. - Caucasus, Turkey, Iran, Turkmenistan, AfghanistanOnopordum corymbosum Willk. - France, SpainOnopordum cynarocephalum Boiss. & Blanche - Palestine, Lebanon, Syria, Israel, JordanOnopordum cyrenaicum Maire & Weiller - LibyaOnopordum dissectum Murb. - Spain, MoroccoOnopordum dyris Maire - MoroccoOnopordum elongatum Lam.Onopordum eriocephalum Rouy - FranceOnopordum espinae Coss.Onopordum heteracanthum C.A.Mey. - Caucasus, Lebanon, Turkey, Syria, Palestine, Iran, Afghanistan, Saudi ArabiaOnopordum horridum Viv. - ItalyOnopordum illyricum L. - Illyrian thistle, Illyrian cottonthistle - MediterraneanOnopordum leptolepis DC. - from Palestine to Altay + XinjiangOnopordum macracanthum Schousb. - Spain, Portugal, Italy, Morocco, AlgeriaOnopordum macrocanthum d'Urv.Onopordum macrocephalum Eig - Palestine, Lebanon, Syria, Israel, JordanOnopordum mesatlanticum Emb. & Maire - MoroccoOnopordum micropterum Pau - Spain, Canary IslandsOnopordum minor L. - IranOnopordum myriacanthum Boiss. - Greece, Turkey, BulgariaOnopordum nervosum Boiss. - Moor's cottonthistle - Spain, PortugalOnopordum parnassicum Boiss. & Heldr. - Greece, TurkeyOnopordum platylepis Murb. - Libya, TunisiaOnopordum polycephalum Boiss. - TurkeyOnopordum prjachinii Tamamsch. - Uzbekistan, Kyrgyzstan, TajikistanOnopordum seravschanicum Tamamsch. - Uzbekistan, Kyrgyzstan, TajikistanOnopordum sibthorpianum Boiss. & Heldr. - Greece, Sicily, Malta, Turkey, North Macedonia, Saudi ArabiaOnopordum tauricum Willd. - Turkish thistle, Taurian thistle, Taurus cottonthistle, bull cottonthistle - southern + central Europe, Ukraine, Middle EastOnopordum turcicum Danin - TurkeyOnopordum wallianum Maire - Morocco
; Natural hybridsOnopordum × brevicaule Onopordum × erectum Onopordum × macronervosum Onopordum × onubense Onopordum × ''spinosissimum''

Invasive problems

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. In North America, there are also Trichosirocalus control programs, but they have proved detrimental to native thistles.