Senecio aurues L. - Golden Ragwort

Senecio aureus plant

Family - Asteraceae

Stems - No info yet.

Senecio aureus stem

Senecio aureus baseBase of plant.

Leaves - Alternate, the basal long petiolate, the cauline sessile. Petioles of the basal leaves to +20cm long, purplish at the base, with a narrow but deep adaxial groove, arachnoid pubescent at the base and sparse pubescent throughout, shaped like a diamond in cross section. Blades of the basal leaves becoming very large, cordate to truncate at the base, shiny deep-green above, light green below, crenate, sparse arachnoid pubescent to glabrous below, glabrous above. Cauline leaves few, becoming sessile and pinnately lobed (lyrate pinnatifid), pubescent as the basal leaves.

Senecio aureus leaves

Inflorescence - Terminal corymbiform cluster of flower heads to +/-10cm broad. Peduncles carinate, glabrous or sparse arachnoid pubescent. Each division of the inflorescence subtended by a linear-subulate bract. Bracts with some arachnoid pubescence near the base.

Involucre - Cylindric to urceolate, +/-8mm long, 4mm in diameter (in flower), uniseriate but with a few small bracts at the base. Phyllaries linear, .5mm broad, united, green, sparse arachnoid pubescent externally, glabrous internally, acute, often brown at the very tip.

Senecio aureus involucreInvolucre.

Ray flowers - Flowers +/-8 per head. Ligule yellow, -1cm long, 3mm broad, oblong-elliptic, 3-toothed at the apex (the teeth .4mm long), glabrous. Corolla tube 4mm long, white, glabrous. Style yellow apically white basally, bifurcate, exserted for about 1mm, the apices spreading and 1mm long. Pappus of white capillary bristles, uniseriate, to 5mm long. Achenes white in flower, cylindric, +2mm long, 4-sided.

Disk flowers - Disk 7mm broad. Receptacle flat. Corolla tube of florets 5-6mm long, white basally, yellow apically, contracted in the basal 2/3-3/4, expanded at the apex, glabrous in and out, 5-lobed. Lobes acute spreading, .75mm long and broad, triangular. Stamens 5, adnate at the base of the expanded portion of the corolla tube. Filaments 1.2mm long, glabrous, translucent-white, very thin at the base, expanded in the apical portion. Anthers 2mm long, yellow, connate around the style. Style partially exserted beyond the anthers, glabrous, whitish basally, yellow apically, to 7mm long, bifurcate in the apical 1mm. Stigmas capitate, small. Pappus and achenes as the ray flowers.

Senecio aureus flowers

Flowering - April - June.

Habitat - Moist or low ground along spring branches, streams, wet ledges, and bluffs. Also in low wet woods and wooded ravines.

Origin - Native to U.S.

Other info. - This striking species can be found scattered throughout much of Missouri but is most common in the southeastern half of the state. The plant is easy to identify becasue of its numerous yellow flowers, big basal leaves, wet habitat, and stoloniferous growth. The plant can form large colonies when left untouched. The big basal leaves can get up to 20cm broad and are cordate to truncate at the base. The pubescence of the plant is variable.
A modern synonym is Packera aurea (L.) A. Love & D. Love

Photographs taken at Whetstone Creek Conservation Area, Callaway County, MO., 5-4-04.


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