Asclepias incarnata, Swamp Milkweed

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Swamp Milkweed is a showy milkweed that grows with lush fragrant vigor in moist to wet soil along streamsides, riverbanks, ditches, and swamps, though it usually does fine in average to moist garden soil. Its rosy pink flowers attract scores of nectar-feeders from mid-summer to early fall, including native bees, butterflies, wasps, flies, hummingbirds, and more. And, of course, the leaves host the caterpillar and chrysalis phases of the Monarch Butterfly (Danaus plexippus).

Cultivation

Showy & Reliable

Swamp Milkweed forms strong roots, making it vigorous and enduring even in average garden soil, though it prefers moisture and can tolerate wetland conditions. Full sun will bring out best flower production, blooming pale to deep pink in mid- to late-summer and early fall. Like other milkweeds, the seed pods, which begin as long green pointed leathery capsules, turn brown as the foliage turns yellow then brown in early fall. The fall form of this plant is not showy, though not as messy-looking as the Common Milkweed (Asclepias syriaca). But the glistening white milkweed fluff, so characteristic of the season, has its own charm, and will self-sow readily in the right conditions. If you do not want this, simply cut the pods while still green.

Taxonomy

In Virginia, Asclepias incarnata occurs as two subspecies: Asclepias incarnata var. incarnata and Asclepias incarnata var. pulchra. Pulchra is the variation which grows commonly on the coastal plains and in freshwater tidal marshes, although var. incarnata has been collected near the coast along the Chesapeake Bay rivers. Both varieties are found in Floyd County, Virginia, according to the Digital Atlas of the Virginia Flora.

Ecology

Wetland Rehabilitation

Asclepias incarnata is described in an NRCS fact sheet as an excellent wetland rehabilitation plant, which means it combines vigor with the ability to hold banks by virtue of its thick spreading root masses, while providing widespread ecosystem services. “The plants have specialized roots which function in heavy, wet soils. The scented, thick, white roots are in environments low in oxygen. Blooming occurs in mid- through late summer and after blooming long, relatively thin, rounded follicles are produced that grow uprightly. They split open in late summer through late fall, releasing seeds attached to silky hairs, which act as parachutes that carry the seeds in wind currents.” (Wikipedia.org)

Conservation Biological Control

The milkweeds are masters at supporting wasps and other insect predators which are vital to keeping an ecosystem strong and balanced. This is also known as “Conservation Biological Control.” Read the Xerces Society’s handbook Habitat Planning for Beneficial Insects as well as Heather Holm’s Pollinators of Native Plants: Attract, Observe and Identify Pollinators and Beneficial Insects with Native Plants.