Hummingbird clearwing (Hemaris thysbe) on Swamp milkweed, Asclepias incarnata

Swamp milkweed

Posted on

Pictured above: Hummingbird clearwing (Hemaris thysbe) on Swamp milkweed (Asclepias incarnata). Photo by Mary Keim. Click on terms for botanical definitions. View post as a PDF.

Sometimes known as Pink milkweed, Swamp milkweed is an erect, herbaceous perennial with striking blooms that makes a great addition to a moist, sunny landscape. It occurs naturally in floodplain swamps, hydric hammocks, wet pine flatwoods and marshes, and typically blooms in summer.

Queen butterflies on Aquatic milkweed, Asclepias incarnata
Queen butterflies nectar on Swamp milkweed flowers. Photo by Mary Keim

Swamp milkweed’s showy pink flowers are slightly fragrant. They are born in compact terminal or axillary umbels. Individual flowers have reflexed corollas and an upright corona — a characteristic typical of milkweed flowers. Leaves are long (up to 6 inches), elliptic to lanceolate, and glabrous. They are oppositely arranged. Stems are stout, glabrous and multi-branched. Seeds are flat and brown with silky white hairs attached. They are born in follicles that split open when ripe. Seeds are dispersed when their silky hairs catch the wind.

It is excellent for attracting butterflies and other pollinating insects. It is an important nectar source butterflies, including Pipevine, Spicebush, and Eastern swallowtails. Native sweat bees, leafcutter bees, and yellow-faced bees forage the flowers for pollen and nectar. Also, Like all members of the Asclepias genus, Swamp milkweed is a larval host plant for Monarch, Queen and Soldier butterflies. The plant contains a milky latex that is toxic to most animals, but Monarch, Queen and Soldier caterpillars are adapted to feed on them despite the chemical defense. Learn more about Monarchs and Milkweed in Florida here.

Family: Apocynaceae (Dogbane family)
Native range: Most peninsular counties, Wakulla and Leon counties
To see where natural populations of Swamp milkweed have been vouchered, visit www.florida.plantatlas.usf.edu.
Lifespan: Perennial
Soil: Moist to wet, well-drained soils
Exposure: Full sun to minimal shade
Growth habit: 4–6’+ tall, not as wide
Propagation: Collect seeds from plants once follicles split. Germinate on top of soil with a light mix barely covering seeds. Seeds can be stored in the refrigerator for a couple of months.
Florida regions of landscape suitability: North, Central, South
Garden tips: Swamp milkweed is one of our most striking native milkweeds. It does best in mixed butterfly and wildflower gardens planted in moist sunny landscapes, but can tolerate occasional drought once established. The plant does well in a container.
Caution: Do not confuse this plant with the nonnative Tropical milkweed (Asclepias curassavica), which is typically sold at retail garden centers. Tropical milkweed does not die back in winter in Florida (as do native milkweeds) and can encourage overwintering in adult Monarchs. It also is linked to the transmission of the Ophryocystis elektroscirrha (OE) infection.

Swamp milkweed is available from nurseries specializing in Florida native plants. Visit www.PlantRealFlorida.org to find a grower in your area.

Learn more about Swamp milkweed from the Florida Native Plant Society and the Institute for Regional Conservation

For information on other Asclepias species, see these resources:

Clasping milkweed

Clasping milkweed (Asclepias amplexicaulis) is a late spring- through summer- blooming milkweed that occurs in dry sandy areas from sandhills to pine savannahs, open woodlands and fallow fields.
Read more… Clasping milkweed

Florida milkweed

Florida milkweed (Asclepias feayi) is a dainty endemic at home in the sandhills and scrubby flatwoods of Central and South Florida. It emerges from winter dormancy in spring and typically blooms mid-summer.
Read more… Florida milkweed

Fewflower milkweed

Fewflower milkweed (Asclepias lanceolata) is a delicate wildflower found in swamps and moist to wet pinelands and prairies throughout Florida. Its stunning orange flowers typically bloom late spring through fall.
Read more… Fewflower milkweed

Swamp milkweed

Swamp milkweed (Asclepias perennis) blooms in late spring through early fall and attracts many pollinators. It is a larval host plant for Monarch, Queen and Soldier butterflies.
Read more… Swamp milkweed
Savannah milkweed's greenish-yellow, urn-shaped flowers

Savannah milkweed

With its diminutive stature and greenish-yellow flowers, Savannah milkweed (Asclepias pedicellata) is oft overlooked in its native pineland and prairie habitats. It blooms late spring through fall, peaking in summer.
Read more… Savannah milkweed
Green antelopehorn in flower.

Green antelopehorn

Green antelopehorn (Asclepias viridis) is an herbaceous perennial wildflower found in pinelands, pine rocklands and disturbed areas in a few Florida counties. It flowers winter through summer, with peak blooms in spring.
Read more… Green antelopehorn

Longleaf milkweed

Longleaf milkweed (Asclepias longifolia ) is a deciduous perennial wildflower that occurs naturally in bogs, moist to wet flatwoods and prairies. It typically blooms in spring but may bloom well into summer or early fall.
Read more… Longleaf milkweed
Whorled milkweed in flower.

Whorled milkweed

Whorled milkweed (Asclepias verticillata ) is one of the smaller, more delicate native milkweeds and is easily overlooked when not in bloom. It flowers late spring through summer and into early fall.
Read more… Whorled milkweed

Butterflyweed

Butterfly milkweed (Asclepias tuberosa) is a perennial that produces large, showy clusters of bright orange to reddish flowers from spring through fall. It occurs naturally in sandhills, pine flatwoods, and other sandy uplands.
Read more… Butterflyweed