Polymnia canadensis L.

Polymnia canadensis plant

Family - Asteraceae

Stems - To 1.5m tall, multiple from base, erect to ascending, fistulose, viscid pubescent above, glabrescent to sparse pilose below, herbaceous.

Polymnia canadensis stemUpper stem.

Leaves - Opposite, petiolate, stipulate. Stipules dentate, connate, sheathing (at least in lower leaves), pubescent. Petioles to +10 cm long, glandular puberulent, green to purplish near base. Blades pinnately lobed, to +25cm long, +/-20cm broad. Lobes acute to acuminate, irregularly and shallow serrate-dentate to entire. Blade tissue decurrent on petiole for +/-2cm or blade with two additional small lobes at base. Upper most leaves undivided, shallow serrate to entire, ovate.

Polymnia canadensis leaves

Polymnia canadensis stipuleLeaf stipule.

Inflorescence - Loose terminal cymose arrangement of flower heads. Each division of inflorescence subtended by a reduced foliaceous bract. Branches of inflorescence densely viscid glandular pubescent.

Involucre - To 7mm tall (long), 7-8mm in diameter. Phyllaries +/-3, linear-lanceolate, to 1cm long, striate-nerved, entire, glandular and simple pubescent, ciliate-margined. Chaffy bracts subtending the ray florets to +1cm long, densely glandular pubescent, ciliate-margined, cupping the achenes.

Polymnia canadensis involucreInvolucre.

Ray flowers - Pistillate and fertile. Ligule white, to +1cm long or reduced and +/-1mm long, 3 lobed at apex, densely pubescent. Achene 3-ribbed, 3-angled, ovoid, pubescent, to -4mm long, much larger than achene of disk flowers. Pappus absent.

Polymnia canadensis flowersFlower head with showy ligules.

Disk flowers - Staminate. Corolla pale yellow, scarious. Corolla tube to 3.5mm long, mostly glabrous, expanded at apex into 5-lobes. Lobes acute, -1mm long, glandular pubescent near margins. Stamens 5, adnate at base of expanded portion of corolla tube. Filaments white to pale yellow, .3mm long. Anthers yellow, connate around style, exserted, 1.8mm long. Styles undivided to shallowly 2-lobed at apex. Achenes white, thin, 2.5-3mm long, glabrous. Receptacle small, convex. Chaff scarious, erose at apex, 6-7mm long, compressed.

Polymnia canadensis flowers

Flowering - May - October.

Habitat - Moist slopes, moist woods, almost always associated with limestone substrata.

Origin - Native to U.S.

Other info. - Look closely at the disk flowers and you will notice that the styles are undivided, which is an indication that they are sterile. This is always something to look for when trying to identify plants in the Asteraceae.
There are two forms of this species in Missouri. Form radiata (Gray) Fassett has the showy ray ligules. Form canadensis has reduced ray ligules. Both forms are common in Missouri.

Photographs taken in the Ozark Scenic Riverways, 5-27 and 6-3-03.


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