Asclepias amplexicaulis Smith - Clasping Milkweed

Asclepias amplexicaulis plant

Family - Asclepiadaceae

Stems - From a deep rhizome, simple, single from the base, erect, herbaceous but stout, to -1m tall, +/-1.5cm in diameter at the base, glabrous, glaucous, with copious milky sap when bruised or crushed.

Asclepias amplexicaulis stem

Leaves - Opposite, sessile, clasping, spreading, typically 2-5 pairs on the stem below the inflorescence, thick, to 12cm long, 8cm broad, broadly oblong to oblong-ovate, glabrous, dark-green and glossy adaxially, light green and glaucous abaxially. Midrib lighter in color and contrasting with the leaf tissue. Lateral veins with a reddish tint, anastomosing before the leaf margin. Margins sinuate-crispate. Apex rounded to sub-acute, with a mucro to 1mm long.

Asclepias amplexicaulis leafAdaxial leaf surface.

Asclepias amplexicaulis leafAbaxial leaf surface.

Inflorescence - Single terminal umbel with 15-80 flowers. Pedicels to 4.5cm long, +/-1mm in diameter, slightly expanded at the apex, puberulent to tomentose but often on just 1/2 or 2/3 of the circumference (the rest glabrous).

Flowers - Petals 5, reflexed, 1cm long, 4-6mm broad, elliptic, appearing glabrous but actually with a very minute pubescence abaxially, glabrous adaxially, greenish-red, with a slightly inflated tip. Sepals 5, reflexed, hidden by the petals, lanceolate, +/-2mm broad, +/-3mm long, green to reddish, glabrous abaxially, sparse appressed-pubescent adaxially. Hoods pinkish-purple, 4-5mm long, +2mm broad, with a wavy apical margin, glabrous. Horns exserted from the hoods +/-3mm, converging over the column, purple. Column +/-3mm tall, -3mm in diameter. Pollinia 2-2.5mm long. Anther sacs brownish-gold. Terminator purple, .5-.6mm long.

Asclepias amplexicaulis flower

Asclepias amplexicaulis flower

Flowering - April - July.

Habitat - Prairies, glades, rocky open woods, roadsides, railroads.

Origin - Native to U.S.

Other info. - This attractive species can be found scattered throughout much of Missouri. It can be easily identified by its erect, glabrous stems, sessile, clasping leaves, and pinkish flowers. The flowers typically occur in a single terminal inflorescence. The leaves have undulate-crispate margins and are rounded at the apex. All parts of the plants bleed white milky sap when injured.

Photographs taken at Fort Benning, GA., 5-15-05.


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