4. Crepis tectorum L. (narrow-leaved hawksbeard)

Pl. 255 i, j; Map 1065

Plants annual or biennial. Stems 10–100 cm long, erect or ascending, few- to many-branched, not sticky, sparsely to densely but inconspicuously pubescent with cobwebby hairs (the minute hairs sometimes few-branched), at least toward the base and just below the heads, often also with short, spreading, gland-tipped hairs toward the branch tips. Basal leaves 3–15 cm long, sessile or more commonly short-petiolate, the blade usually irregularly pinnately lobed, the lobes spreading, mostly narrow, bluntly to sharply triangular, the surfaces glabrous or sparsely and inconspicuously pubescent with minute, curled to cobwebby hairs. Inflorescences usually appearing paniculate, less commonly the heads appearing in loose clusters at the branch tips. Inner series of involucral bracts 12–15, 6–9 mm long, finely appressed-hairy on the inner surface, the outer surface glabrous or more commonly pubescent with minute, cobwebby hairs, often also with a longitudinal band of short, spreading, gland-tipped hairs, these with somewhat broadened bases, nearly transparent to light brownish yellow, the outer series of bracts much shorter than to about 1/2 as long as the inner series. Receptacle with minute hairs around the base of each floret. Ligulate florets 30–70, the corolla 9–13 mm long. Pappus 4–5 mm long. Fruits all similar or nearly so, 2.5–4.0 mm long, narrowly oblong-elliptic in outline, not beaked or only slightly short-beaked, not expanded at the tip, 10(–12)-ribbed, the ribs usually minutely roughened or barbed, reddish brown to dark brown, with an abrupt, lighter yellowish tip. 2n=8. June–July.

Introduced, uncommon, known thus far from Jefferson County and the city of St. Louis (native of Europe, Asia; introduced sporadically in the U.S. [mostly in northern states], Canada). Railroads and open, disturbed areas.

This species was first reported by Steyermark (1963) in the supplement to his Flora of Missouri, based on a collection by Viktor Mühlenbach from the St. Louis railyards.