8. Rudbeckia subtomentosa Pursh (sweet coneflower)
Pl. 288 c, d;
Map 1224
Plants
perennial, with fibrous roots and stout rhizomes. Stems 50–200 cm long,
moderately to densely pubescent with short, spreading hairs, at least above the
midpoint, not glaucous. Leaves mostly (or occasionally only the lowermost
leaves) deeply 3-lobed or deeply divided, mostly angled or tapered at the base,
only slightly expanded at the base and inconspicuously wrapping around the
stem, the margins otherwise sharply and finely to coarsely toothed, the
surfaces (especially the undersurface) moderately to densely pubescent with
short, spreading, minutely pustular-based hairs, often also minutely
gland-dotted, moderately to strongly roughened to the touch, green to grayish
green when fresh. Basal and lowermost stem leaves often absent at flowering,
long-petiolate, the blade 15–30 cm long, 30–100 mm wide, ovate to broadly ovate
or elliptic in outline, the lobes ovate to narrowly elliptic or lanceolate,
tapered to a sharply pointed tip. Median and upper stem leaves short- to
long-petiolate, the uppermost leaves occasionally sessile, the blade 2–20 cm
long, 1–120 mm wide, the unlobed leaf blade or the lobes of a divided blade
lanceolate to ovate to elliptic, tapered to a sharply pointed tip.
Inflorescences mostly appearing as loose, open clusters or leafy panicles.
Involucral bracts 15–25, 5–15 mm long, lanceolate to nearly linear, the outer
surface and margins densely pubescent with short, usually minutely
pustular-based hairs. Receptacle 10–17 mm long, 8–16 mm in diameter, usually
hemispherical at the start of flowering, then elongating somewhat and becoming
more or less conical. Chaffy bracts subtending only the disc florets, shorter
than to nearly as long as the disc florets (including the corolla), angled to a
short, usually sharply pointed tip, the outer surface and margins with dense,
short, often somewhat matted hairs, dark purple toward the tip or rarely dull
greenish yellow (see discussion below). Ray florets 12–20, the corolla 20–40 mm
long, usually relatively slender, spreading or slightly drooping at flowering,
yellow to orangish yellow, the outer surface sparsely short-hairy and
moderately minutely gland-dotted. Disc florets numerous, the corolla 3.0–4.5 mm
long, yellowish green toward the base (or rarely throughout), normally dark
purple to purplish brown toward the tip, the lobes spreading to curled downward
at flowering. Stigma lobes relatively short and usually sharply pointed at the
tip. Pappus a minute rim or crown. Fruits 2.0–3.5 mm long. 2n=38. July–October.
Scattered nearly
throughout the state (Kansas to Texas east to Michigan and Alabama, possibly
also North Carolina; introduced in New England). Bottomland forests, edges of
mesic upland forests, upland prairies, banks of streams and rivers, margins of
ponds and lakes, and fens; also pastures, ditches, railroads, and roadsides.
Rare plants with
the disc corollas and chaffy bracts dull yellow to yellowish green have been
called R. subtomentosa f. craigii (Sherff) Fernald. This form
originally was described based on plants collected in 1910 by Moses Craig in
St. Louis County. It may still be known only from the original site, where
plants historically grew with more typical plants having purple disc florets
and chaffy bracts.