Cirsium discolor (Muhl. ex Willd.) Spreng.

Field thistle

Cirsium discolor plant

Family - Asteraceae

Stem - Erect, to 3 m, well branched, glabrous or sparsely pubescent with spreading hairs.

Cirsium_discolor_stemStem.

Leaves - Basal and alternate. Basal leaves to 50 cm long, narrowly ovate to elliptic or obovate, deeply lobed, the margins otherwise coarsely toothed and spiny, the upper surface appearing green, pubescent with stiff, straight hairs, the undersurface appearing white, densely pubescent with felty hairs. Stem leaves well developed, the main leaves to 25 cm long, those toward the branch tips usually somewhat reduced, deeply lobed, somewhat clasping and often slightly decurrent at the base, otherwise like the basal leaves.

Cirsium_discolor_basalsBasal rosette.

Cirsium_discolor_leavesStem leaves.

Cirsium_discolor_leaf1Leaf abaxial.

Cirsium_discolor_leaf2

Inflorescences - Usually solitary heads, terminal on branch tips, nearly sessile, discoid, numerous.

Cirsium_discolor_headsHeads.

Cirsium_discolor_headDeveloping head.

Involucres - Urn shaped, 25-35 mm long, about as long as wide, often somewhat cobwebby-hairy, the lower and median bracts tapered to a spreading, spiny tip, straw-colored to light yellow, usually also somewhat sticky along the midrib.

Cirsium_discolor_involucreInvolucre and florets.

Florets - Ray florets absent. Disk corollas 25-32 mm long, pinkish, the lobes 6-9 mm long. Pappus of bristles, 18-25 mm long, white or nearly so.

Cirsium_discolor_floretsFlorets.

Fruits - To 5.5 mm long, somewhat 4-angled and flattened in cross-section, the tip usually with an angular rim or raised crown surrounding a small, knoblike or conical projection.

Flowering - July - November.

Habitat - Forest openings, prairies, glades, fields, pastures, roadsides, open disturbed areas.

Origin - Native to the U.S.

Other info. - This large thistle is most common in the eastern half of the state, and in fact Missouri lies near the western edge of its natural range. It is characterized by large involucres with spiny bracts and deeply lobed leaves with white undersides. A white leaf underside on any Missouri thistle signifies a native species. The coloration is caused by a dense covering of felty hairs.

Thistles can be unpleasant to work with because of their spininess; however, they are greatly beneficial to wildlife. Hummingbirds obtain nectar from the flowers, and goldfinches and other bird species relish the seeds. The flowering plants also attract numerous insects. Steyermark noted that young shoots and leaves could be cooked and eaten.

Photographs taken by DETenaglia; also at West Tyson County Park, St. Louis County, MO, 8-31-2018 and 9-4-2018 (SRTurner).



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