Solidago ptarmicoides (Nees) Boivin

Solidago ptarmicoides plant

Family - Asteraceae

Stems - Herbaceous, erect, to +60cm tall, from a thick caudex, simple below but branching in the apical 1/2 (inflorescence), terete, 2-4mm n diameter, typically multiple from the base, glabrescent at the base, scabrous and pubescent in the apical 1/2, with many small antrorse multicellular (use a lens to see) trichomes, light green and often with darker green vertical striations.

Solidago ptarmicoides stem

Leaves - Alternate, petiolate. Lowest leaves long petiolate. Petioles narrowly winged by decurrent leaf tissue, mostly glabrous. Blades linear-elliptic, with a few coarse but shallow teeth or entire, somewhat scabrous from the thickened bases of the hairs, antrorse strigillose on the margins. Leaf and petiole combined to +15cm long, 1cm broad. Cauline leaves reduced upward, becoming scale-like in the inflorescence. All leaves with a cartilaginous margin approximately .1mm broad. Light from underneath to see this.

Solidago ptarmicoides leaves

Inflorescence - Corymbose arrangement of flower heads. Peduncles bracteate with reduced leaves, often with some arachnoid pubescence.

Involucre -To +/-6mm long and broad, cupulate to cylindric. Phyllaries imbricate, appressed, oblong, acute at the apex, to 5mm long, 1.4mm broad, glabrous externally, with a few appressed hairs or glabrous internally. Margins entire or minutely ciliolate, mostly scarious in the middle portion, with darker green apices, pale at the base.

Solidago ptarmicoides involucreInvolucre.

Ray flowers - +/-12 per flower head, pistillate, fertile. Ligules glabrous, white, 5-7mm long, 2-3mm broad. Corolla tube white, +/-2mm long, glabrous. Pistil glabrous, becoming purple towards the apex, to 2.7mm long, bifurcate at the apex for +/-.4mm. Achene to +1mm long in flower, white, glabrous. Pappus of numerous capillary bristles. Bristles white, barbellate, -5mm long.

Disk flowers - Disk 6mm broad, with many flowers. Corolla 4mm long, pale yellow in the apical 1/2, greenish basally, glabrous externally and internally, 5-lobed. Lobes acute, .5mm long, erect to slightly spreading. Stamens 5, adnate at the base of the corolla tube. Filaments translucent, 2-2.2mm long, glabrous, compressed. Anthers connate around the style, 1.5-1.9mm long, yellow, drying to brown. Style to 4mm long, greenish-translucent, glabrous, bifurcate in the apical 1mm. The stigmas erect. Achenes glabrous, ribbed, 1-1.3mm long in flower, greenish-white. Pappus of capillary bristles. Bristles barbellate, to 4mm long, white. Receptacle flat, naked, -2mm broad.

Solidago ptarmicoides flowers

Flowering - July - September.

Habitat - Rocky prairies, glades, bluffs, rocky open woods.

Origin - Native to U.S.

Other info. - This small species of Solidago can be found in the Ozark region of Missouri. The plant is unusual for a Goldenrod as the flowers are white instead of the typical yellow, and the flower heads are quite large for a Solidago. Because of these characteristics, the plant used to belong to the genus Aster. The old name was Aster ptarmicoides (Nees) T. & G.

Photographs taken near Stegal Mountain, Shannon County, MO., 9-12-03.


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