Cirsium longistylum

Perennials monocarpic, 40–150 cm; taprooted. Stems usually 1, erect, less commonly several, ascending, simple to sparingly short-branched in distal 1/2, less commonly openly branched, villous with jointed trichomes; branches on distal stems 0–many, short, ascending. Leaves: blades linear to oblong or elliptic, 10–30+ × 1–10 cm, margins flat to undulate, subentire to coarsely dentate or shallowly to deeply pinnatifid, lobes lance-oblong to broadly triangular, spinulose to spiny-dentate or shallowly lobed, main spines 3–12 mm, abaxial faces green and subglabrous to gray- or white-tomentose with felted arachnoid trichomes, ± villous to tomentose along major veins with septate trichomes, rarely glabrous or glabrate, adaxial ± green, glabrous or villous with septate trichomes; basal often present at flowering, spiny winged-petiolate or sessile; principal cauline well distributed, proximally winged-petiolate, distally sessile, gradually reduced, bases sometimes short-decurrent (0–2 cm); distal ± reduced, often narrower than the proximal, sometimes with non-pigmented bases. Heads several–many, erect, usually in racemiform or spiciform arrays, usually closely subtended by clustered ± leafy bracts. Peduncles 0–15+ cm. Involucres (green), broadly ovoid, 1.5–2.5 × 1.5–2.5 cm, loosely villous with septate trichomes, sparingly if at all arachnoid. Phyllaries in 4–8 series, subequal, ± lanceolate, bases appressed, apices ascending, linear to broadly expanded, erose to lacerate or spiny-fringed, spines straight, slender, 2–3 mm, abaxial faces with or without narrow glutinous ridge; apices of inner flexuous, sometimes expanded and erose. Corollas white, ochroleucous, 19–23 mm, tubes 6.5–8.5 mm, throats 7.5–11 mm, lobes 4–5 mm; style tips 4–5.5 mm, conspicuously exserted. Cypselae brown, 5.5–6.5 mm, apical collars not differentiated; pappi 17–20 mm. 2n = 34.

Phenology: Flowering summer (Jun–Aug).
Habitat: Moist soil, roadsides, meadows, forest edges and openings
Elevation: 1500–2400 m

Distribution

• Generated Map
• Legacy Map

Mont.

Discussion

Of conservation concern.

Cirsium longistylum is endemic to the Big Belt, Castle, Elkhorn, and Little Belt ranges of west-central Montana. It is highly variable, and several authors have suggested that it has introgressed with one or more other species (R. J. Moore and C. Frankton 1963; J. M. Poole and B. L. Heidel 1993; S. J. Brunsfeld and C. T. Baldwin, unpubl.). It is closely related to C. hookerianum, and the two probably share a common ancestry or a history of hybrid interactions dating back to the Pleistocene. Cirsium longistylum is perhaps also affected by modern or historic introgression involving C. scariosum var. scariosum.

Selected References

None.

Lower Taxa

None.