Cirsium pumilum var. hillii

(Canby) B. Boivin

Naturaliste Canad. 94: 646. 1972.

Common names: Hill’s thistle
Endemic
Basionym: Cnicus hillii Canby Gard. & Forest 4: 101. 1891
Synonyms: Cirsium hillii (Canby) Fernald Cirsium pumilum subsp. hillii (Canby) R. J. Moore & Frankton
Treatment appears in FNA Volume 19. Treatment on page 117. Mentioned on page 116.

Plants mostly 25–60 cm, branches 0–4, short. Roots often tuberous-thickened. Leaves usually shallowly lobed, main spines ± fine, 3–6 mm. Heads 5–7 cm. Phyllaries: outer 3–6 mm wide at base, spines slender, 1.5–3 mm. Corollas usually 45–55 mm. Cypselae usually 4.5–5 mm. 2n = 30.


Phenology: Flowering summer (Jun–Aug).
Habitat: Sandy or gravelly soils, prairies, limestone barrens, pastures, pine barrens, open woods, and oak savannas
Elevation: 200–400 m

Distribution

V19-68-distribution-map.gif

Ont., Ill., Ind., Iowa, Mich., Minn., Wis.

Discussion

Variety hillii occurs mainly in prairie areas from Minnesota and Iowa east to southern Ontario, Michigan, and northern Indiana. It has often been treated as a species distinct from Cirsium pumilum. As R. J. Moore and C. Frankton (1966) pointed out, the differences separating these taxa are, for the most part, metric characters that show considerable overlap. Some specimens, especially those from Ohio and western Pennsylvania, are difficult to place, and scattered individuals within the area of var. pumilum would readily be assigned to var. hillii were they growing in the area of that taxon. Moore and Frankton chose to recognize the infraspecific taxa within C. pumilum as subspecies, a rank that is seldom employed in North American Cirsium taxonomy.

Hill’s thistle is a taxon that has attracted the attention of conservationists because of declining populations. Although the U.S. Fish and Wildlife Service determined in 1999 that this plant does not warrant elevation to Candidate Species status, it is recognized as a species of concern in several states. Throughout much of its range the populations have declined due to habitat destruction and fragmentation that have accompanied agricultural development and urbanization.

Selected References

None.

Lower Taxa

None.

"fine" is not a number."[" is not declared as a valid unit of measurement for this property."]" is not declared as a valid unit of measurement for this property."broad" is not a number.

middle +  and outer +
arachnoid +  and villous +
subglabrous +, tomentose +, arachnoid +  and villous +
short-tailed +
spineless +  and twisted +
dentate +, entire +  and spine-tipped +
ascending +  and spreading +
innermost +
scarious +
colored +  and yellow +
corymbiform +, paniculiform +, subcapitate +, spiciform +  and racemiform +
indeterminate +  and determinate +
David J. Keil +
(Canby) B. Boivin +
auriculate-clasping +
tapered +
Cnicus hillii +
compound +  and simple +
5 cm50 mm <br />0.05 m <br /> (30 cm300 mm <br />0.3 m <br />) +
less undulate;shallowly deeply pinnatifid +
2cm;10cm +
10-nerved or 20-nerved +  and rugose +
tawny +  and white +
Hill’s thistle +
actinomorphic +
pink +  and purple +
4.5 cm45 mm <br />0.045 m <br /> (5.5 cm55 mm <br />0.055 m <br />) +
stramineous +  and brown +
compressed +  and ovoid +
fertile +  and bisexual +
Ont. +, Ill. +, Ind. +, Iowa +, Mich. +, Minn. +  and Wis. +
200–400 m +
gray-canescent +  and glabrous +
pistillate +, staminate +  and neuter +
winged +  and beaked +
dispersed +
Sandy or gravelly soils, prairies, limestone barrens, pastures, pine barrens, open woods, and oak savannas +
indeterminate +
5 cm50 mm <br />0.05 m <br /> (7 cm70 mm <br />0.07 m <br />) +
each +  and sessile +
2.5 cm25 mm <br />0.025 m <br /> (3 cm30 mm <br />0.03 m <br />) +
broadly cylindric;ovoid +
3.5 cm35 mm <br />0.035 m <br /> (5 cm50 mm <br />0.05 m <br />) +
sessile +  and petiolate +
cauline +  and basal +
bristle-tipped +
lobed +, spinose-dentate +, ovate +  and broadly triangular +
0.3 cm3 mm <br />0.003 m <br /> (0.6 cm6 mm <br />0.006 m <br />) +
entire +  and dentate +
usually lobed +  and dissected +
0.3 cm3 mm <br />0.003 m <br /> (0.6 cm6 mm <br />0.006 m <br />) +
2-carpellate +
persistent +
3.5 cm35 mm <br />0.035 m <br /> (4.5 cm45 mm <br />0.045 m <br />) +
0 cm0 mm <br />0 m <br /> (15 cm150 mm <br />0.15 m <br />) +
Flowering summer (Jun–Aug). +
middle +  and outer +
weakly to strongly +
papillate +  and smooth +
Naturaliste Canad. +
bearing subulate enations +, hairy +  and bristly +
flat;convex +
glutinous +
tuberous-thickened +
tawny;white +
setiform +  and plumose +
exalbuminous +
subequal +
0.15 cm1.5 mm <br />0.0015 m <br /> (0.3 cm3 mm <br />0.003 m <br />) +
spiny-winged +, simple +  and branched +
appendaged +  and truncate +
dilated +  and swollen +
enlarged +
0.3 cm3 mm <br />0.003 m <br /> (0.7 cm7 mm <br />0.007 m <br />) +
Cirsium hillii +  and Cirsium pumilum subsp. hillii +
Cirsium pumilum var. hillii +
Cirsium pumilum +
variety +
cylindric +
expanded +
1.1 cm11 mm <br />0.011 m <br /> (1.5 cm15 mm <br />0.015 m <br />) +
flexuous +
erose-denticulate +
expanded +
bristly-dentate to coarsely +
slender +
2 cm20 mm <br />0.02 m <br /> (3.5 cm35 mm <br />0.035 m <br />) +
perennial +, perennating +  and biennial +
25 cm250 mm <br />0.25 m <br /> (100 cm1,000 mm <br />1 m <br />) +