Rudbeckia hirta L. - Back-Eyed Susan
Family - Asteraceae
Stems - Multiple from base,
erect, herbaceous, scabrous, hirsute to papillose-hispid (hairs with purple
swollen bases), branching, carinate, to +1m tall.
Leaves - Alternate, petiolate
to sessile, serrate to subentire, hirsute to papillose-hispid, scabrous.
Lowest leaves with long petioles. Blade to 15cm long, 5cm broad, lance-elliptic
to broadly lanceolate or oblong, with tissue contracted in lower 1/5 of
blade.. Upper leaves becoming sessile, linear-lanceolate.
Inflorescence - Single large flower head terminating stem, on long peduncle.
Involucre - Outer phyllaries
reflexed, scabrous, hirsute to papillose-hispid, to 2.5cm long, 5-6mm broad,
linear-oblong. Inner phyllaries smaller, spreading.
Involucre.
Ray flowers - Sterile. Ligule
yellow, to +4cm long, 1cm broad, 3-toothed at apex, appressed pubescent
below, glabrous above. Achene 2.1mm long, 1.3mm broad(in flower). Pappus
absent.
Disk flowers - Disk to 1.8cm
in diameter, broadly ovoid to hemispheric, flowers fertile. Disk corollas
4.5mm long, dark purple-brown at apex, 5-lobed. Lobes acute. Style brown,
bifurcate (the divisions subulate-attenuate). Achenes black, 1.8mm long (in
flower), glabrous, subterete to 4-angled. Pappus absent. Receptacle conic.
Chaff to 7mm long, purplish-brown, pubescent at apex.
Flowering - May - October.
Habitat - Open woods, thickets, waste ground, rocky prairies, meadows, pastures, slopes, roadsides, railroads, also cultivated.
Origin - Native to U.S.
Other info. - This hardy
plant is extremely popular in cultivation and is very common in the wild.
The species is classified as biennial but can grow as an annual also. It
readily grows from seed. This species fairly closely resembles R.
fulgida Ait. but the latter grows wild only in the southern
1/3 of the state and prefers moist to wet habitats. There are other differences
between the two species also but habitat is really a good determining factor.
Photographs taken in Minimum, MO., 5-31-03.
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