Asclepias stenophylla Gray - Prairie Milkweed

Asclepias stenophylla plant

Family - Asclepiadaceae

Stems - Erect, herbaceous, terete, green to purple in strong sun, retrorse pubescent, with white milky sap, simple, to +/-60cm tall, 2 to 3mm in diameter.

Asclepias stenophylla stem

Leaves - Alternate, sessile or very short petiolate, retrorse pubescent, typically ascending. Blades linear, 10-13cm long, 2-3mm broad, typically conduplicate, antrorse pubescent (sparsely), green, acute.

Asclepias stenophylla leaves

Inflorescence - Short pedunculate umbels in the upper leaf axils. Peduncles to 2mm long, densely retrorse pubescent. Umbels with 10-15 flowers. Rays of umbels subtended by linear subulate bracts. Bracts dense antrorse pubescent, to 5mm long, 1mm broad at base. Rays to +/-7mm long, densely retrorse pubescent.

Asclepias stenophylla inflorescence

Flowers - Whitish green. Petals 5, spreading with the tips incurved, greenish-white, glabrous, elliptic, to 5mm long, +2mm broad. Hoods greenish white, -4mm long. Horns essentially absent or not exceeding the lobes of the hoods. Anther column greenish, 4mm broad, 2-3mm in diameter. Pistils 2, glabrous. Pollinia 2mm long (total). Anthers sacs yellow, -1mm long. Terminator dark purple. Sepals 5, alternating with the lobes, pubescent externally, glabrous internally, lanceolate to subulate, to 3mm long and 1mm broad at the base. Fruits not seen.

Asclepias stenophylla flower

Flowering - June - July.

Habitat - Dry, rocky prairies, glades, ledges of bluffs, usually on basic soils.

Origin - Native to U.S.

Other info. - This species can be found mainly in the Ozark region of Missouri. It is not as common as other milkweeds in the state but can be found in good quality glade and prairie habitats. The plant can be identified by its simple, retrorse pubescent stems, thin, opposite leaves, and small clusters of white flowers.

Photographs taken at Busiek State Forest, MO., 6-17-05.


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