The Cirsium genus is commonly known as the "thistle" genus, Cirsium being the Greek word for 'thistle.'
The genus's most infamous species is R. conicus which is a controversial agent of biological pest control which has been used against noxious thistles in the genera Carduus, Cirsium, Onopordum, and Silybum.
Several plant taxa are endemic to Steens Mountain, including Castilleja pilosa var. steenensis, Cirsium peckii, Draba cusickii var. cusickii, Penstemon davidsonii var. praeteritus, and Poa chambersii.
It is a biological pest control agent that was introduced into the United States in 1974 to control exotic thistles, especially in the Cirsium and Carduus genera.
Cirsium | Cirsium arvense | Cirsium palustre | Cirsium occidentale | Cirsium eriophorum | Cirsium acaule | A mined leaf of ''Cirsium vulgare |
They are polyphagous in herbaceous plants, mainly feeding on Carduus nutans (hence the specific name) and Silybum marianum, as well as on Salvia, Urtica and Cirsium species.
Cirsium muticum is as host for some species of butterflies and moths, including the swamp metalmark butterfly (Calephelis muticum), a species that is currently undergoing risk assessment in the United States.
Cirsium vulgare (Spear Thistle) is a species of the genus Cirsium, native throughout most of Europe (north to 66°N, locally 68°N), western Asia (east to the Yenisei Valley), and northwestern Africa (Atlas Mountains).
The adults feed on the flower nectar of various flowers, including Silene, Carduus, Cirsium and Scabiosa species.
The main species in the plant communities here are Upright brome (Bromus erectus), Sheep's Fescue (Festuca ovina), Quaking-grass (Briza media), and downland herbs such as Burnet-saxifrage (Pimpinella saxifraga), Salad-burnet (Sanguisorba minor), Common Milkwort (Polygala vulgaris) and Dwarf Thistle (Cirsium acaule).
The larvae feed on seeds and seed coats within the flower heads of various Cirsium species (including Cirsium canescens and Cirsium occidentale) and closely related genera.
They feed on the nectar of various flowers, including Salvia columbariae, Asclepias cordifolia, Ribes aureum, Dichelostemma capitatum, Clarkia, Vicia, Cirsium and Stachys species.