Swamp Milkweed (Asclepias incarnata) Growing & Care Guide for Gardeners
Article by Dean Ravenscroft, Ph.D. - Updated 31st Jan 2024
- Plant Characteristics: A tall, herbaceous perennial with clusters of small, fragrant, pink to mauve flowers. It is especially known for being a vital host plant for Monarch butterflies, providing food for their caterpillars.
- Growing & Care: Prefers moist, well-drained soils and full sun. While it is named for its preference for swampy areas, it is surprisingly drought-tolerant. It's a low-maintenance plant that can thrive in a variety of garden settings.
- Tips for New Gardeners: An excellent choice for beginners interested in supporting butterfly populations. Requires little care once established. Be mindful that the sap is toxic if ingested and can irritate skin.
Asclepias incarnata, commonly known as Swamp milkweed, Rose or Pink milkweed, Swamp silkweed, or Rose milkflower is an herbaceous perennial and part of the Apocynaceae family (Dogbanes).
Asclepias incarnata typically grow from two to four feet (0.6 to 1.2 m) high, making them excellent border plants.
Asclepias incarnata plants, photograph by peganum; CC.
Swamp milkweed are a perfect go-to plant for butterfly gardens as it is a major food source for caterpillars of the Monarch butterfly.
Its floral nectar also attracts other pollinators and hummingbirds.
Plants carry fragrant blooms and can be found naturally in abundance in wet meadows, marshes, swamps, and flood plains from the east coast and as far west as the Rocky Mountains, and in southern Canada.
Asclepias incarnata, flower photograph by Fritz Flohr Reynolds.
Plants are tall-stemmed with numerous lance-shaped leaves. They typically bloom from early summer through to mid-autumn.
Asclepias incarnata, display clusters of small flowers with color variations from light pinks to light purples. (A notable exception is Ice Ballet, a popular nursery selection that produces white blossoms; this plant does not grow in the wild).
Self-seeding occurs after blooming, the plant produces elongated pods that later split releasing seeds on silken threads to be carried on the wind.
Swamp Milkweed, photograph by USFWS Mountain-Prairie; CC.
Gardener's HQ Guide to Growing Swamp Milkweed
Asclepias incarnata can be planted in the spring or autumn / fall in moist soils and in a sunny or partial shaded location.
Be aware that if planted in the spring, the plants will concentrate their energies on developing a strong root system, with leaves appearing later in the process.
To plant Swamp milkweed a hole should be made that is twice the size of the plant's root ball, and buried so that the root ball's top is even with the soil top. Fill in the soil applying firm pressure.
Gardeners should choose their planting location carefully, as these plants, with their deep root systems tend to be difficult to transplant. Beyond that advice, they require little care.
Photograph of a Swamp Milkweed flower being visited by a Great Spangled Fritillary butterfly by Joshua Mayer; CC.
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Asclepias incarnata Growing and Care Guide
- Scientific Name: Asclepias incarnata.
- Common Name: Swamp milkweed.
- Growing Zone: USA: 3 to 8.
- Life Cycle / Plant Type: Perennial.
Plant Details
- Plant Height (Inches): 30 to 48.
- Plant Spread (Inches): 12 to 24.
- Time of Bloom: Middle of summer to early autumn.
- Flower Details: Pink, Purple.
- Leaf Foliage: Green.
- Fruit:
- Growth Form: Upright / erect.
Ideal Growing Conditions
- Best Light Conditions: Partially shady to full sunlight.
- Rate of Growth: Average pace.
- Suitable Soil Types: Loamy, Neutral.
- Soil Moisture: Moist/Wet.
Caring Conditions
- Care:
- Level of Maintenance: Low.
- Propagation: Seeds.
- How to Prune: Not usually required.
- Pests:
- Diseases:
Further Information
- Can Attract: Monach butterflies.
- Tolerant of: Deer, Clay Soil, Wet Soil, bogs.
- Best Garden Use: Border, Foundation, En masse.
- Family: Apocynaceae.
- Closely Related Species: Adenium, Allamanda, Amsonia, Asclepias, Nerium, Pachypodium, Wrightia, Vinca.
I hope that you enjoyed this guide on how to grow Asclepias incarnata. You may also enjoy the following Asclepias growing guides: How to grow Asclepias curassavica, Butterfly Flower, and Asclepias syriaca.
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