Senecio plattensis Nutt. - Prairie Ragwort
Family - Asteraceae
Stems - To 50cm tall, simple
to branching near apex, fistulose, erect, with dense arachnoid pubescence
below and also scattered along the stem and in the axils of the branches
and leaves, with shallow ridges, from slightly thickened roots.
Lower stem.
Leaves - Alternate. Basal
leaves long petiolate. Petioles to +10cm long, densely arachnoid pubescent
at base and less so above. Blade undivided, elliptic-lanceolate to elliptic-ovate,
to 6.5cm long, 2.5cm broad, serrate, villosuous below to glabrous, thickened (subsucculent).
Cauline leaves deeply divided (pinnatifid to bipinnatifid), petiolate below,
becoming sessile above, densely arachnoid pubescent at base, with scattered
arachnoid pubescence on rest of leaf or appearing glabrous on lobes, thickened (subsucculent).
Lobes typically shallowly lobed again, entire.
Middle and upper leaves of stem.
Inflorescence - Numerous
flower heads in a corymbiform cyme terminating stems. Branches of inflorescence
with floccose-arachnoid pubescence in axils. Peduncles with minute linear
bracts often subtending flower heads.
Involucre - Cylindrical,
6-7mm tall(long), 6-7mm in diameter, truncate at base. Phyllaries in a single
series, connate for most of length, arachnoid pubescent at least at base,
with scarious acuminate tips.
Involucre.
Ray flowers - Typically 13
per flower head, fertile. Ligules to 1cm long, 3mm broad, truncate or with
a shallow notch at apex, orangish-yellow. Achenes densely clavate pubescent.
Pappus of barbed capillary bristles to 5mm long.
Disk flowers - Disk to 8mm
in diameter. Flowers fertile. Corollas orange-yellow, 5-lobed. Lobes acute.
Achenes clavate pubescent. Pappus of numerous barbed capillary bristles.
Receptacle flat.
Flowering - May - June.
Habitat - Dry upland prairies, bluffs, rocky open woods, glades, loess hills.
Origin - Native to U.S.
Other info. - This species
can be found scattered throughout Missouri. It may be difficult to distinguish
from some other species of Senecio but the dense arachnoid
pubescence at the base of the stems and leaves and in the inflorescence
is a good characteristic to look for. Also, the leaves will typically have
some pubescence at least abaxially. The basal leaves are also undivided
in this species.
Photographs taken off Hwy U in Benton County, MO., 5-15-04.
|