Asclepias sullivantii Englem.
Family - Asclepiadaceae
Stems - To 1m tall, erect, from a large crown and a deep rhizome, herbaceous but stout, typically simple, typically single from the base, to +1cm in diameter at the base, glabrous, green and sometimes glaucous, solid, with copious milky sap.
Leaves - Opposite, sessile, glabrous, entire, to +15cm long, to 8cm broad, lanceolate to oblong, green above, glaucous-blue below, with a blunt to rounded apex but with a small, triangular mucro. Midrib whitish and clearly differentiated from the other leaf tissues. Veins anastomosing about 3-4mm from the leaf margin.
Inflorescence - Pedunculate umbels from the upper leaf axils. Umbels with +/-20 flowers. Peduncles to 4-5cm long, glabrous, green. Rays of the umbel subtended by small lanceolate bracts. Bracts to +5mm long, +?-2mm broad, acute, glabrous. Rays (pedicels) purplish, +/-2cm long, glabrous.
Flowers - Petals 5, reflexed, +/-1cm long, 5-6mm broad, acute, glabrous, purplish. Sepals 5, 5mm long, to 3mm broad, acute, subulate, glabrous, reflexed, hidden by the petals. Hoods pinkish, +/-6mm long, glabrous. Horns exserted from the hoods about 4mm, converging over the anther head. Anther column to -5mm long, 4mm in diameter. Pollinia 3mm long. Terminator .8mm long, deep purple. Anther sacs -2mm long.
Flowering - June - August.
Habitat - Wet meadows, uplands, river bottoms, prairies, alluvial thickets.
Origin - Native to U.S. and Canada.
Other info. - This attractive species of milkweed can be found mainly in the northern half of Missouri. The plant can be identified by its completely glabrous parts, and big flowers. The flowers are fewer in number and larger than than those of the similar A. syriaca L.
Photographs taken off Hwy 70, Callaway County, MO., 8-12-06.