Gray Green Thistle - Cirsium canovirens
Other Names:
Cirsium cymosum, Cirsium subniveum, Cirsium inamoenum
Native Species
Global Rank:
G4G5
State Rank:
S3S4
(see State Rank Reason below)
C-value:
4
Agency Status
USFWS:
USFS:
BLM:
External Links
Taprooted biennial. Stems erect, branched above or not, 30–100 cm, sometimes with spiny wings from leaf bases. Herbage tomentose to arachnoid, upper leaf surfaces sometimes sparsely so. Leaves short-petiolate; blade linear-oblanceolate, 8–25 cm long, pinnately lobed, becoming clasping or decurrent upward. Inflorescence heads 1 to few at tips of peduncles forming corymbiform arrays; peduncles 1–8 cm long. Involucres broadly campanulate, 15–30 mm high, sparsely arachnoid-tomentose; phyllaries imbricate in 6 to 10 series, green, linear-lanceolate; sometimes with a darkened, often resinous midvein; spines 2–6 mm long, spreading. Disk corollas white to light purple, 15–26 mm long. Achenes 5–8 mm long (
Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).
NATIVE versus NON-NATIVE THISTLES [
Parkinson and Mangold 2015]
Native Thistles* Plants grow relatively sparsely and possess few or gentler spines, intermix with many plant species, and are slow to colonize disturbed ground.
* Flowers provide nectar and pollen for numerous native birds and insects, and forage for some wildlife. For example, elk eat the flowers of Elk Thistle.
* Involucral bracts tend to adhere to the flower head for most of their length (except for the spine).
* Plants are
not rhizomatous except for Flodman’s Thistle which can produce horizontal runner roots.
Non-native Thistles* Plants colonize disturbed ground quickly, often form dense patches, and produce nastier spines - limiting recreational activities, injuring people/animals, and reducing native plant species diversity.
* Flowers provide nectar and pollen for some birds and insects, but not forage for wildlife or livestock.
* Some species are aggressively rhizomatous and outcompete native plants that provide nutritional forage.
* Require management to control, reduce, or remove. Refer to the MANAGEMENT subsection.
DIFFERENTIATING THISTLE GENERACarduus* Stems: Winged.
* Pappus: Barbellate - minutely barbed, narrow bristles. Bristles usually fall separately.
* Flower Head - Receptacle: Not obviously fleshy or honeycombed. Densely bristly. In the flower head, look for bristles between the florets.
Cirsium* Stems: Winged or not winged.
* Pappus: Feathery (plumose) - fine, long hairs on each side of the central axis (rib).
* Flower Head - Receptacle: Densely bristly. In the flower head, look for bristles between the florets.
Onopordum* Stems: Spiny and winged along their entire length.
* Pappus: Barbellate - minutely barbed, narrow bristles. Bristles connected at base.
* Flower Head - Receptacle: Definitively fleshy and honeycombed. No or very sparse and short bristles. In the flower head, look between the florets to find nothing.
POLLINATORS The following animal species have been reported as pollinators of this plant species or its genus where their geographic ranges overlap:
Bombus vagans,
Bombus appositus,
Bombus auricomus,
Bombus bifarius,
Bombus borealis,
Bombus centralis,
Bombus fervidus,
Bombus flavifrons,
Bombus frigidus,
Bombus huntii,
Bombus mixtus,
Bombus nevadensis,
Bombus rufocinctus,
Bombus sylvicola,
Bombus ternarius,
Bombus terricola,
Bombus sitkensis,
Bombus occidentalis,
Bombus pensylvanicus,
Bombus bimaculatus,
Bombus griseocollis,
Bombus impatiens,
Bombus insularis,
Bombus suckleyi,
Bombus bohemicus, and
Bombus flavidus (Thorp et al. 1983, Mayer et al. 2000, Wilson et al. 2010, Colla and Dumesh 2010, Colla et al. 2011, Koch et al. 2012, Williams et al. 2014, Tripoldi and Szalanski 2015).
