Summary
Swamp milkweed (Asclepias incarnata) is an erect, clump forming herbaceous perennial that thrives in wet sites, but is adaptable to normal garden soils as well. With a branching habit, stems reach 3-4′ tall and spread 2-3’ wide. It is tolerant of partial shade, but the best floral display occurs in full sun.
During early to mid summer, leafy stems are topped with branching clusters of uniquely shaped and fragrant, pink to rose-purple flowers. The flowers will develop into attractive, vertically positioned, 4” tall seed pods that split open and release their abundant, silky-tufted seeds to the wind when mature. Flowers are a nectar source for butterflies, several wasp, bee, and fly species, and occasionally hummingbirds. The foliage of this and other milkweeds is the sole food source for the monarch butterfly caterpillar.
Leaves and stems exude a milky sap that is mildly toxic, making it unfavored by deer and rabbits. If you grow milkweed, you will certainly experience oleander aphids. They are easily controlled by hosing them off the plant with a gentle, fine stream of water. Plants develop a deep taproot and do not transplant easily once established. For the mixed border with adequate moisture, combine with downy skullcap (Scutellaria incana) and queen-of the-prairie (Filipendula rubra). Allow it to intermingle with wild germander (Teucrium canadense) and Virginia mountain-mint (Pycnanthemum virginianum) in a swale garden. Zones 3-8.
Swamp milkweed is split into two varieties; pulchra and incarnata. Eastern swamp milkweed (Asclepias incarnata var. pulchra) can be recognized by its broader, more ovoid shaped leaves, pubescent stems and leaves, and shorter habit. Western swamp milkweed (Asclepias incarnata var. incarnata) tends to be taller, lacks noticeable pubescence and the leaves are longer and more narrow. All cultivars of swamp milkweed originate from Western swamp milkweed. The cultivar Asclepias incarnata ‘Ice Ballet’ has white flowers instead of the pinkish purple flowers.
More Details
- Plant Type
perennial - Sun/Shade Conditions
full-sun, part-shade - Foliage Character
deciduous - Soil Moisture
average, wet - Flowering Period
late-summer, mid-summer - Soil PH
adaptable - Flower Color
light-purple, pink - Summer Foliage Color
green - Fall Foliage Color
green - Fruit/Seed Color
brown
Additional Information
Lady Bird Johnson Wildflower Center, Illinois Wildflowers, Missouri Botanical Garden
Western swamp milkweed (Asclepias incarnata var. incarnata): Lady Bird Johnson Wildflower Center
Eastern swamp milkweed (Asclepias incarnata var. pulchra): Lady Bird Johnson Wildflower Center