Asclepias verticillata L. - Whorled Milkweed

Asclepias verticillata plant

Family - Asclepiadaceae

Stems - To +/-60cm tall, erect, herbaceous, from rhizomes and fleshy roots, branching in upper 1/2, with short pubescence in vertical lines from between leaf bases. Internodes short.

Asclepias verticillata stemPortion of stem.

Leaves - Sessile to short petiolate, (the petioles to -2mm long), linear, in whorls of 3-6 at each node, glabrous or with some pubescence, +/- 7cm long, 2-3mm broad, acute, with single prominent midrib. Margins revolute creating a terete effect.

Asclepias verticillata leaves

Inflorescence - Axillary pedunculate umbels. Peduncles to +3cm long, pubescent. Flowers typically 10-20 per umbel. Pedicels purplish at base, 8-9mm long, pubescent. Typically 0-2 bracts present at the base of the umbels. Bracts linear and short.

Asclepias verticillata inflorescence

Flowers - Petals greenish-white, purplish at apex, elliptic-oblong, 4-5mm long, 2mm broad, recurved with the tips slightly spreading, glabrous to minutely puberulent at the base internally,(use a lens to see). Hoods white, to 1.5mm long, glabrous. Horns white, 1.7mm long, loosely converging over anther column. Anther column greenish, white at apex, 2mm long. Pollinia 1.2mm long, translator deep purplish-brown. Pistils 2, glabrous, greenish, 2mm long. Follicles to 10cm long, 1cm broad.

Asclepias verticillata flowers

Flowering - May - September.

Habitat - Prairies, pastures, open woods, roadsides, railroads.

Origin - Native to U.S.

Other info. - This attractive little species can be found throughout Missouri. Like most of the species in this family the plant is toxic. This is one of the most easily recognized members of the genus because of the thread-like, whorled leaves. Because it handles dry conditions very well, A. verticillata would make a fine garden specimen. Many flying insects are attracted to its flowers.

Photographs taken at the "Narrows", Oregon County, MO., 6-28-03.


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