Rudbeckia amplexicaulis Vahl

Clasping Coneflower

Rudbeckia amplexicaulis plant

Family - Asteraceae

Stems - Erect, multiple from base, branching, herbaceous, glabrous, often glaucous, light green with darker green striate nerves, terete, solid, annual from a taproot.

Rudbeckia amplexicaulis stem

Leaves - Alternate, sessile, auriculate-clasping. Lowest leaves elliptic, shallow serrate, to +10cm long, 3-4cm broad, gradually reduced upward, light green, acute, with antrorse strigose margins. Upper leaves becoming ovate.

Rudbeckia amplexicaulis leaves

Rudbeckia amplexicaulis leaf

Inflorescence - Single, long-peduncled, terminal flower head. Peduncle expanded just below the involucre.

Involucre - +/-2cm broad, with +/-10 phyllaries. Phyllaries spreading, subulate, 3-8mm long, +/-2mm broad at base, entire, glabrous, with antrorse strigose margins.

Rudbeckia amplexicaulis involucre

Ray flowers - +/-8 per flower head. Ligule oblong, 1-2cm long, +/-1cm broad, orangish-yellow and red to maroon at the base, antrorse pubescent below, glabrous above. Corolla tube 1mm long, pubescent externally with yellowish hairs. Pappus absent. Achene 2mm long in flower, 4-angled, pubescent on the angles.

Rudbeckia amplexicaulis flowers

Disk flowers - Disk conical at first and quickly becoming columnar, to +3cm tall, to +1.5cm in diameter. Flowers 5-lobed. Corolla tube glabrous externally, whitish green in the basal half, purplish with darker purple nerves in the apical half. Lobes spreading to reflexed, .3-.5mm long, .2mm broad at base, acute, yellow internally. Stamens 5, adnate near the base of the corolla tube. Filaments white, glabrous, -1mm long. Anthers dark purple, 1.5mm long, connate around the style, partially exserted. Style translucent in basal half, purple in apical half, 2mm long, bifurcate. Stigmas 2mm long, dark purple, pubescent in apical half. Pappus absent. Achene glabrous, white in flower, 2mm long in flower. Mature achene black, glabrous, +?-3mm long. Receptacle glabrous, with chaff. Chaff acute, translucent-white with two dark stripes near the margins and green at the apex, ciliolate at the apex, glabrous below, +/-5mm long.

Rudbeckia amplexicaulis disk

Flowering - June - July.

Habitat - Prairies, chert barrens along streams, waste ground, roadsides.

Origin - Native to U.S.

Other info. - This attractive species can be found in just a few western Missouri counties in the prairie region. The plant is easy to identify becasue of its clasping leaves and distinctive columnar disks. It is an easy species to grow and would make a good garden subject.

Photographs taken off Hwy 21 near Selma, AL., 6-4-05.