Swamp Milkweed, Pink Milkweed, Marsh Milkweed, Swamp Butterfly Weed
Asclepias incarnata, commonly known as Swamp Milkweed, is a stunning, moisture-loving perennial that plays a crucial role in supporting monarch butterflies and other pollinators. Native to North America, this milkweed species thrives in wet meadows, riverbanks, and marshy areas, making it an excellent choice for rain gardens and naturalized landscapes.
Milkweed plants belong to the Apocynaceae family, which includes other flowering plants such as oleander, hoya, plumeria, and the desert rose.
Swamp Milkweed is an erect, clump-forming perennial that stands out for its tall, graceful stems, showy blooms, and narrow, lance-shaped leaves. It produces brilliant clusters of lilac-pink star-shaped flowers atop upright branching stems, creating a magnet for pollinators. The flowers are rich in nectar and fragrant, often emitting a light vanilla scent. After flowering, Swamp Milkweed produces elongated, spindle-shaped seed pods, which remain through winter, eventually splitting open to release silky-haired seeds.
Unlike Asclepias syriaca (Common Milkweed), Swamp Milkweed is more restrained in its growth habit and does not spread aggressively via rhizomes, making it an excellent choice for well-maintained pollinator gardens.
Swamp Milkweed is native to Manitoba, Quebec, and Nova Scotia, extending south through New England to Georgia, west to Louisiana and Texas, and north to North Dakota. Thriving in wetlands, damp meadows, marshes, and stream banks, this adaptable species plays a crucial role in wetland restoration and rain garden projects, supporting biodiversity.
Swamp Milkweed’s tall and elegant growth habit makes it ideal for the back of flower borders or naturalized meadow plantings.
After blooming, Swamp Milkweed produces elongated seed pods that split open to release silky-haired seeds, which are dispersed by the wind. These seedpods add late-season interest to the garden and provide food for birds and small mammals.
The foliage serves as a larval host for monarch butterfly caterpillars, which feed exclusively on milkweed species.
Swamp Milkweed thrives in USDA hardiness zones 3-9, making it highly adaptable across a wide range of climates. It is exceptionally cold-hardy and can withstand harsh winters, making it a reliable perennial for northern regions. In warmer climates, it remains resilient as long as it receives adequate moisture
Swamp Milkweed is a powerhouse for wildlife, offering both habitat and food for various species. Monarch butterfly caterpillars rely on its leaves as a primary food source, while adult monarchs and other butterflies feast on its nectar-rich flowers. Native bees are frequent visitors, benefiting from the plant’s abundant nectar supply. In addition to pollinators, Swamp Milkweed supports beneficial predatory insects that naturally help control garden pests, contributing to a balanced and healthy ecosystem.
Discover more plants that attract butterflies.
Swamp Milkweed has low toxicity but contains cardiac glycosides and resinoids, which can cause nausea, vomiting, diarrhea, weakness, and confusion if ingested in large amounts. Its milky sap may cause contact dermatitis and eye irritation. Toxic parts include flowers, fruits, leaves, roots, seeds, and stems. Harmful to humans, cats, dogs, and horses.
Monarch butterfly caterpillars store these toxins in their bodies, making them unpalatable to predators.
Swamp Milkweed is naturally resistant to deer and rabbits due to its milky sap, which contains toxic cardiac glycosides.
Swamp Milkweed is not invasive and does not spread aggressively like other milkweed species. It self-seeds modestly but remains manageable in most garden settings.
Swamp Milkweed is a must-have for pollinator gardens. With its showy pink blooms, essential role in supporting monarchs, and easy-care nature, it brings both beauty and ecological benefits to any landscape. Whether planted in wet meadows, rain gardens, or perennial borders, this native wildflower is a stunning and practical choice.
Milkweed: Is it Right for Your Garden? Pros and Cons Explained
Swamp Milkweed can be propagated through seeds, cuttings, and division. Here’s how to propagate this plant using these methods:
From Seeds
Cold Stratification: Swamp Milkweed seeds require a period of cold stratification to break dormancy. Place the seeds in a moist medium, such as vermiculite or perlite, and store them in a refrigerator at 35–38°F (1.5–3.3°C) for 4 to 12 weeks.
Sowing: After stratification, sow the seeds just beneath the soil surface in seedling trays filled with a well-draining seedling mix. Maintain ambient temperatures between 65–75°F (18–24°C) and keep the soil consistently moist. Germination typically occurs within a few weeks.
From Cuttings
Selecting Cuttings: During the summer, choose healthy, green stems approximately 1/3 inch (0.8 cm) in diameter.
Preparation: Cut the stems underwater to prevent air embolism and dip the cut ends into a rooting hormone to encourage root development.
Planting: Insert the treated cuttings into a moist medium such as sand, vermiculite, or potting soil. Ensure the medium remains consistently moist throughout the rooting period.
Root Development: Roots typically develop within 6–10 weeks, after which the new plants can be transplanted to their permanent location.
By Division
Timing: The optimal time to divide Swamp Milkweed is in late spring when the plant is actively growing.
Process: Carefully dig up the entire plant, ensuring minimal disturbance to the root system. Gently separate the clump into smaller sections, each containing at least one healthy stem and a portion of the root system.
Replanting: Immediately replant the divisions at the same depth they were growing previously, and water them thoroughly to help establish the roots.
While division is possible, it’s important to note that Swamp Milkweed has a deep taproot, making it somewhat sensitive to disturbance. Therefore, division should be done cautiously to avoid damaging the plant.
No serious pest or disease issues.
Monarch butterflies lay their eggs on both Swamp Milkweed (Asclepias incarnata) and Common Milkweed (Asclepias syriaca), but they often prefer Common Milkweed due to its broader leaves and abundant foliage for caterpillars. However, adult monarchs are highly attracted to the nectar of Swamp Milkweed flowers.
Swamp Milkweed thrives in full sun and moist, well-drained soil. It is best suited for rain gardens, wet meadows, pond edges, and damp low-lying areas where water naturally collects.
Swamp Milkweed typically grows between 3 to 5 feet (0.9 to 1.5 meters) tall, depending on soil moisture and growing conditions.
| Hardiness |
3 - 9 |
|---|---|
| Plant Type | Perennials |
| Plant Family | Apocynaceae |
| Genus | Asclepias |
| Common names | Swamp Milkweed, Milkweed |
| Exposure | Full Sun |
| Season of Interest | Summer (Mid, Late) |
| Height | 3' - 5' (90cm - 150cm) |
| Spread | 2' - 3' (60cm - 90cm) |
| Spacing | 36" (90cm) |
| Maintenance | Low |
| Water Needs | Average |
| Soil Type | Clay, Loam |
| Soil pH | Acid, Alkaline, Neutral |
| Soil Drainage | Moist but Well-Drained, Moisture Retentive, Poorly Drained |
| Characteristics | Fragrant, Showy |
| Native Plants | United States, New York, New Jersey, New Hampshire, Maryland, Vermont, Rhode Island, Pennsylvania, Connecticut, Delaware, Massachusetts, Maine, Rocky Mountains, Pacific Northwest, Southeast, Northeast, Southwest, Midwest, Illinois, Kansas, Indiana, Ohio, Michigan, North Dakota, South Dakota, Wisconsin, Nebraska, Iowa, Missouri, Minnesota, Idaho, West Virginia, Virginia, Georgia, Florida, Arkansas, Alabama, Kentucky, North Carolina, South Carolina, Tennessee, Louisiana, Nevada, Texas, Oklahoma, New Mexico, Utah, Montana, Wyoming, Colorado |
| Tolerance | Deer, Rabbit, Clay Soil, Wet Soil |
| Attracts | Bees, Butterflies |
| Garden Uses | Beds And Borders, Bog Gardens, Ponds And Streams, Rain Gardens |
| Garden Styles | Prairie and Meadow, Informal and Cottage |
| Hardiness |
3 - 9 |
|---|---|
| Plant Type | Perennials |
| Plant Family | Apocynaceae |
| Genus | Asclepias |
| Common names | Swamp Milkweed, Milkweed |
| Exposure | Full Sun |
| Season of Interest | Summer (Mid, Late) |
| Height | 3' - 5' (90cm - 150cm) |
| Spread | 2' - 3' (60cm - 90cm) |
| Spacing | 36" (90cm) |
| Maintenance | Low |
| Water Needs | Average |
| Soil Type | Clay, Loam |
| Soil pH | Acid, Alkaline, Neutral |
| Soil Drainage | Moist but Well-Drained, Moisture Retentive, Poorly Drained |
| Characteristics | Fragrant, Showy |
| Native Plants | United States, New York, New Jersey, New Hampshire, Maryland, Vermont, Rhode Island, Pennsylvania, Connecticut, Delaware, Massachusetts, Maine, Rocky Mountains, Pacific Northwest, Southeast, Northeast, Southwest, Midwest, Illinois, Kansas, Indiana, Ohio, Michigan, North Dakota, South Dakota, Wisconsin, Nebraska, Iowa, Missouri, Minnesota, Idaho, West Virginia, Virginia, Georgia, Florida, Arkansas, Alabama, Kentucky, North Carolina, South Carolina, Tennessee, Louisiana, Nevada, Texas, Oklahoma, New Mexico, Utah, Montana, Wyoming, Colorado |
| Tolerance | Deer, Rabbit, Clay Soil, Wet Soil |
| Attracts | Bees, Butterflies |
| Garden Uses | Beds And Borders, Bog Gardens, Ponds And Streams, Rain Gardens |
| Garden Styles | Prairie and Meadow, Informal and Cottage |
How many Asclepias incarnata (Swamp Milkweed) do I need for my garden?
| Plant | Quantity | |
|---|---|---|
| Asclepias incarnata (Swamp Milkweed) | N/A | Buy Plants |
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Create a membership account to save your garden designs and to view them on any device.
Becoming a contributing member of Gardenia is easy and can be done in just a few minutes. If you provide us with your name, email address and the payment of a modest $25 annual membership fee, you will become a full member, enabling you to design and save up to 25 of your garden design ideas.
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