Cirsium mohavense
Cirsium barnebyi
Mohave thistle, Mojave thistle, Rusby's thistle, virgin thistle
Barneby's thistle
1–several, erect, proximally simple, distally branched, ± densely gray-tomentose;
branches 0–many, ascending to spreading.
1–few, erect, gray-tomentose or glabrate;
branches few, above middle, ascending.
blades oblong-elliptic to oblanceolate, 10–60 × 2–15 cm, unlobed and merely spinulose or spiny-dentate or shallowly to deeply pinnatifid, lobes linear-lanceolate to ovate-triangular, spreading, entire to coarsely dentate, main spines slender to stout, 3–30 mm, faces ± gray-tomentose, sometimes ± glabrate;
basal often present at flowering, winged-petiolate;
principal cauline decreasing distally, proximal winged-petiolate, distal sessile, bases decurrent as spiny wings 1–5 cm;
distalmost well separated, bractlike.
blades oblong-elliptic, 10–35 × 2–7 cm, strongly undulate, margins shallowly to deeply lobed, lobes 8–15 pairs, linear-lanceolate to broadly triangular, closely spaced, spreading, coarsely spinose-dentate or cleft into 2–5 spine-tipped divisions, main spines 3–5 mm, faces densely gray-white-tomentose;
basal usually present at flowering, winged-petiolate;
principal cauline becoming sessile and progressively reduced distally, bases decurrent as spiny wings to 5 cm;
distal cauline usually much reduced, less lobed.
0–15 cm.
0–4 cm.
ovoid to hemispheric, 1.5–2.5 × 1.5–2 cm, loosely arachnoid on phyllary margins or glabrate.
ovoid to hemispheric or campanulate, 1.7–2 × 1.5–2 cm, loosely arachnoid on phyllary margins or glabrate.
white to pink or lavender, 16–25 mm, tubes 7–12 mm, throats 4–7 mm, lobes 4–8 mm, style tips 3–4 mm.
lavender to pink-purple, 18–28 mm, tubes 7–9 mm, throats 4–8 mm, lobes 5–11 mm;
style tips 3.5–5 mm.
in 5–8 series, imbricate, (inner greenish to brown or stramineous), lanceolate or ovate (outer) to linear-lanceolate (inner), entire, abaxial faces with narrow glutinous ridge;
outer and middle appressed, spines spreading, 3–7 mm;
apices of inner often flexuous, flattened, spineless, scabrid.
in 6–9 series, imbricate, ovate (outer) to linear-lanceolate (inner), entire, abaxial faces with narrow glutinous ridge;
outer and middle appressed, spines ascending to spreading, stramineous, 2–7 mm;
apices of inner often flexuous, narrow, flat, entire, spineless, glabrous.
1–many, in corymbiform or paniculiform arrays.
1–20+, borne singly or clustered at branch tips, in leafy, ± corymbiform arrays.
stramineous to dark brown, 3–6 mm, apical collars 0.2–0.3 mm, yellowish;
pappi 14–16 mm.
tan to brown, 5–5.5 mm, apical collars colored like body, narrow;
pappi 15–23 mm.
= 30, 32.
Cirsium mohavense
Cirsium barnebyi
Of conservation concern.
Cirsium mohavense ranges from scattered sites in eastern California east in the Basin and Range Province of southern Nevada to southwestern Utah and nortwestern Arizona, mostly in Mojave Desert region. When Welsh proposed Cirsium virginense for a geographically limited group of plants from southwestern Utah and northwestern Arizona (and subsequently discovered in extreme southeastern Nevada), he indicated that its relationship to other western thistles was unknown. Subsequently, he indicated (S. L. Welsh 1983; Welsh et al. 1993) that the affinities of the taxon apparently lie with C. mohavense, but he did not attempt to distinguish C. virginense from C. mohavense (in the strict sense) because the latter was not known to occur in Utah. A. Cronquist (1994) attempted the distinction. The only character he used in his key was life span of the plants: biennial (C. mohavense) versus perennial, spreading by creeping roots (C. virginense). In the descriptions of the two taxa he elaborated on this character, indicating that C. mohavense is single-stemmed and C. virginense often multistemmed. In the remaining features the plants are very similar or overlap extensively.
Distinction of two taxa on the basis of duration is impractical and probably inaccurate. Specimens commonly lack roots, and in those specimens in which bases are present, I have seldom been able to make any distinction between biennial taproots and perennial taproots. In particular I have seen no evidence of creeping roots. I am not aware of any study of either taxon that documents the life history of the plants. Some specimens of C. mohavense (in the strict sense) appear to have perennial bases like those attributed to C. virginense by Cronquist. For instance, a specimen of C. mohavense from Death Valley (Thorne & Ratcliff 2287, BRY) is indistinguishable from specimens of C. virginense (e.g., Atwood 13374, BRY) from Nevada and Utah. Both have a branched root crown with multiple rosettes and nearly identical leaves and heads.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Of conservation concern.
Cirsium barnebyi occurs from the southern Rocky Mountains of southwestern Wyoming, northeastern Utah, and northwestern Colorado.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
CA
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