Asclepias incarnata L. - Swamp Milkweed

Asclepias incarnata plant

Family - Asclepiadaceae

Stems - To 1.5m tall, from fibrous roots, erect, herbaceous, glabrous or with a single vertical line of appressed pubescence in the internodes above, with milky sap, branching above.

Asclepias incarnata stem

Leaves - Opposite, petiolate. Petiole to +1.5cm long. Blade to 15cm long, +2cm broad, linear to linear-lanceolate, acuminate, with strigillose margins, sparse appressed pubescent, truncate to rounded at the base.

Asclepias incarnata leaves

Inflorescence - Axillary and terminal umbellate cymes of 20-30 flowers each. Peduncles green, to +5cm long, antrorse appressed pubescent, with one vertical line more densely pubescent than rest of peduncle. Pedicels pinkish-rose, sparse pubescent, to 1.4cm long, subtended by linear bracts. Bracts to 6mm long, pubescent.

Flowers - Petals 5, 6mm long, 2.3mm broad, oblong-elliptic, entire, reflexed, glabrous, pink to purple. Hoods 2mm long, 1.2mm broad, pinkish-white. Horns pinkish-white, to 2.5mm long. Gynostegium to 2.5mm long, 1.3mm in diameter. Pollinia 1.1mm long. Calyx lobes 5, reflexed, 2mm long, pubescent, pinkish-green. Follicles to 8cm long, fusiform, typically glabrous.

Asclepias incarnata flowerFlower close-up.

Asclepias incarnata fruitsFruits.

Flowering - June - August.

Habitat - Moist to wet soils.

Origin - Native to U.S.

Other info. - This species can be found throughout Missouri. The plant is becoming one of the more popular Asclepias in cultivation because of its tall height, striking flowers, and ability to grow in wet soils. It is an obvious butterfly favorite. The flowers of this species are not as large as in some other members of the genus but the plant typically produces many clusters of flowers.

Photographs taken in Brown Summit, NC., 10-12-02, and in the along the shores of the Current River, Shannon County, MO., 8-16-03.


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