Rudbeckia triloba L.

Rudbeckia triloba plant

Family - Asteraceae

Stems - Erect, to +2m tall, branching, herbaceous, from fibrous roots, hirsute to strigose, reddish-green.

Rudbeckia triloba stem

Leaves - Alternate, petiolate below, sessile above, scabrous, strigose. Lower leaves 3-lobed, scabrous, to +/-15cm long, +/-10cm broad. Upper leaves becoming simple, coarse serrate, attenuate, wih ciliate margins, ovate to ovate-lanceolate. Tissue of leaves abruptly contracted at base and winging petiole.

Rudbeckia triloba leaves

Inflorescence - Loose cymose arrangement of single flower heads terminating stem branches.

Involucre - Phyllaries to +/-1cm long, 2.5mm broad at base, in single series, recurving, ciliate-margined, typically 8 in number, scabrous, pubescent to strigose.

Rudbeckia triloba involucreInvolucre.

Ray flowers - Ligule yellow, to +/-2cm long, 7mm broad, notched at apex, glabrous to sparse appressed pubescent below, glabrous above. Achenes to 1.1mm long in flower, glabrous, white, somewhat compressed. Pappus absent or a minute crown. Flowers sterile.

Disk flowers - Disk to 1.2cm in diameter. Corolla deep purple, 5-lobed. Corolla tube to 2.5mm long, glabrous. Lobes acute, .8mm long. Style bifurcate, deep purple. Achene 2mm long in flower, white, glabrous, 4-angled, black in fruit. Pappus absent or a minute crown. Receptacle conic. Chaff whitish below, deep purple at apex, glabrous, to 5.5mm long, acuminate.

Rudbeckia triloba flower

Flowering - June - November.

Habitat - Low wet woods, thickets, rocky slopes, railroads.

Origin - Native to U.S.

Other info. - This is a tall, much-branched plant. The flowers are smaller than any other Rudbeckia in Missouri but the plant is still striking. It would do well in cultivation but it has a tendency to drop its leaves at anthesis and can look pretty ragged. A slightly moist soil will prevent this.
Our plants belong to var. triloba. A southeastern variety, var. pinnatiloba T.& G., has lower leaves with 5-7 lobes.

Photographs taken in the Ozark Scenic Riverways, Shannon County, MO., 8-2-03.


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