Rudbeckia hirta L. - Back-Eyed Susan

Rudbeckia hirta plant

Family - Asteraceae

Stems - Multiple from base, erect, herbaceous, scabrous, hirsute to papillose-hispid (hairs with purple swollen bases), branching, carinate, to +1m tall.

Rudbeckia hirta stem

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.

Rudbeckia hirta involucreInvolucre.

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.

Rudbeckia hirta flower

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.


Back