Asclepias incarnata is also known as swamp milkweed, rose milkweed, rose milk flower, swamp silkweed, or white Indian hemp. It is a herbaceous perennial plant species native to North America that usually grows spontaneously in damp to wet soils, but it can also be cultivated as a garden plant for its attractive pink flowers.
Swamp milkweed is easy to grow in environments with medium to wet soils and plenty of bright direct sunlight. The plant can tolerate well-drained soils, even though the species thrives in swamps and wet meadows, but it will not survive prolonged periods of drought.
If you want your garden full of butterflies, you can grow swamp milkweed and you will be surprised to see how their blooms will attract these beneficial pollinators. You can also grow swamp milkweed for its ornamental characteristics and you can even use it as a cut flower and use its long-lasting blooms to create bouquets and floral arrangements.
Like many other milkweeds, Asclepias incarnata contains latex, a chemical that repels insects and other herbivorous animals, so you can rest assured that these plants will not invite any unwanted guests into your garden.
|Botanical Name||Citrus x Junos|
|Common Name||Swamp milkweed, rose milkweed, rose milk flower, white Indian hemp|
|Plant Type||Herbaceous, perennial wildflower|
|Mature Size||Around 1 meter (3-4 feet) tall and 0.5-1 meter (2-3 feet) wide|
|Sun Exposure||Full sun|
|Soil Type||Moist, loamy, fertile soil|
|Soil pH||Slightly acidic|
|Bloom Time||Mid-summer, Early fall|
|Flower Color||Light pink, light purple|
|Hardiness Zones||3-9 (USDA)|
|Native Area||Canada and US|
About Swamp Milkweed
- Asclepias incarnata is not as invasive as other milkweeds or plants and it grows well in the garden and it will produce attractive blooms for up to 20 years.
- The genus was named after the Greek god of medicine – Aesculapius because some species have been used for a long time to treat a variety of symptoms. The name of the species means “flesh-coloured” in Latin.
- The Asclepias incarnata flowers represent a great source of nectar for bees and are beneficial for pollinating insects and especially butterflies such as Monarchs, Swallowtail butterflies, and Greater Fritillaries. Milkweeds are host plants for the monarch butterfly. Scientists estimate that over the last several decades, the monarch butterfly population has dropped between 20% and 90%, so, planting milkweed in the garden may help the survival of the monarch butterflies.
- Swamp milkweed is also popular with other types of beneficial insects such as native bees, bumblebees, honeybees, wasps, flies, and skippers. Another adorable visitor of the swamp milkweed flowers is the Ruby-Throated Hummingbird.
- What you will need to know if you are considering growing swamp milkweed plants in your own garden is that they are usually considered toxic for dogs, cats and horses. The stems of milkweed exude a toxic milky sap when cut, so it is highly recommended to handle these plants with care and to make sure your curious pets don’t munch on them.
- The dried stems of Asclepias incarnata are used in the textile industry and quality fibres which are used in twine can be obtained from these plants. The seeds can also be used in combination with other fabrics in order to produce textile products or are used to stuff pillows. The seed floss is used to mop up oil spills from contaminated water. The latex contained within the leaves and stems is used to make rubber.
- Asclepias incarnata pairs well with plants like cardinal flower, swamp sunflower, narrow leaves sunflower, mistflower, New England aster, New York aster or lurid sedge.
- Swamp milkweed makes a perfect addition to sunny borders, cottage gardens, wildflower meadows, pond gardens, stream banks, butterfly gardens, and moist sunny areas.
Swamp Milkweed Features: An Overview
- Asclepias incarnata is a perennial wetland plant but will do fine in medium-moist conditions once it establishes. It is native to most of the USA and Eastern Canada.
- Asclepias incarnata is a plant that contains toxic sap that can be harmful to humans and pets in large quantities. However, in the past, people used the roots of swamp milkweed to make a tea that was thought to eliminate parasitic worms.
- Asclepias incarnata is a tall plant, it grows in height between 100 and 150 cm and grows from thick, white roots.
- Typically, its stems are grouped together and from plants that emerge in late spring, after most of the plants have begun their growth for the year.
- The leaves are disposed oppositely along the stem and are 7.5 to 15 cm long and 1 to 4 cm wide, being narrow and lance-shaped, with sharp ends. The leaves of swamp milkweed may turn purple at the end of the summer and fall, but this is a normal occurrence; the green leaves will grow next spring again.
- Swamp milkweed blooms early through mid-summer and produces small, fragrant, pink to mauve ( sometimes even white) coloured small flowers which are rounded umbellate racemes.
- The colours of the flowers vary from dark shades of purple to softer ones or even to pinkish purple and white types may be found as well. The flowers have five reflexed petals and an elevated central crown.
- The flowers of swamp milkweed have a sweet, subtle vanilla scent.
- After the plant blooms, it produces green follicles about 12 cm long, that when ripe, split open. These follicles release light or dark-brown flat seeds which are attached to white hairs that catch the wind. This is a natural mechanism for seed dispersal and it is a commonly encountered way used by other milkweed species too.
Growing Swamp Milkweed
Asclepias incarnata best grows in areas characterized by wetland conditions. In the wild, this plant can be found near swampy areas, bogs and marshes or along banks of ditches and streams. The swamp milkweed has a fleshy taproot system that remains shallow, but there are cases when it can reach a depth of more than 25 cm and it favours loamy soil with high organic matter content.
The soil where the plant will be planted should be moderately moist because this species does not support large periods of time of dryness. Asclepias incarnata best grows close to the shore of a water source, but it can survive in prairies, roadsides and fields.
Swamp milkweed needs full to partial sun conditions, but for maximum growth and development, the plant should have direct sun exposure lasting for up to six hours a day. The preferred soil is slightly acidic, even though the plant can tolerate a pH of up to 8.0 as long as other ambient conditions are optimized. Asclepias incarnata relies on insect pollination for fertilization and disperses its seeds via air.
This plant is a hardy perennial that survives and comes back every year in spring. Even though the foliage is dead and the plant goes dormant in the winter months, the rootstock is still alive and it does not require any special protection during the cold months.
In the fall, it is recommended to prune the stalks to about 15 cm in height in order to discourage monarchs from establishing winter-breeding colonies. With this procedure, you will also eliminate OE spores that may be present on the plant. You can also prepare the plant for winter by adding some high-quality mulch or regular leaves, that are not showing signs of rot, to work as an insulator to keep it from getting too cold.
When it comes to pests, aphids are the most common ones. They damage the plant by sucking liquid from it, stressing it and eventually, if the damage spreads, it can even kill the plant. As a remedy against aphids, once you notice them on your plants, the first thing that you need to try is to hose them off.
If the infestation is not severe, the aphids will fall off the plants without too much effort. In more severe cases of aphid infestations, hose the plants repeatedly and use natural or organic sprays like a soap-and-water mixture, neem oil, or essential oils
Other pests that may attack your plant are whiteflies, scale insects, spider mites, thrips, leaf miners, snails and slugs. As for common diseases, there may appear leaf spots, root rot or verticillium wilt. You can help the plant by removing the affected areas and improving soil quality and drainage as these diseases are fungi that are commonly caused by high levels of humidity.
Planting Swamp Milkweed
Asclepias incarnata is one of the plant species that is planted via seed and purchased from plant nurseries as plug plants. The seed pods have to be collected once they have are dried out and are ready to be cracked open. It is recommended to keep the seeds in a paper bag for approximately two weeks before storing them in a cool, well-ventilated area and keep them away from sun rays for up to 12 weeks. If you want to make the germination faster for the next spring, keep the stored seeds at temperatures between 1 and 3˚C.
The germination stage, you will need an empty germination tray and fill it with about 10 cm of moist substrate. You can use a store-bought seedling mix or a moss-based mix.
For the next stage, after the stratification period is over, spread the seeds on the soil surface, but make sure that there is sufficient space between the seeds. Tap them gently in the soil before coating them with another fine substrate layer.
If moisture and temperature conditions are maintained, seedlings should take between 4 and 8 weeks to properly develop their first leaves. As soon as the little plants are large enough to handle, you can transplant them into individual pots.
- QUALITY - All seeds packaged by Seed Needs are intended for the current and the following growing seasons. All seeds are stored in a temperature controlled facility that is free of significant amounts of moisture.
- QUANTITY - Seed packets by Seed Needs offer generous quantities. You can share with friends and family, or save your extra seeds until the next season, if properly stored.
- PACKETS - This packet displays a beautiful illustration of the variety to be grown, as well as detailed seed sowing information on the reverse side as well. Measures 3.25” wide by 4.50” tall.
- PROMISE - Seed Needs will never knowingly supply GMO based seed products. The vast majority of our seeds are open pollinated & heirloom, with the exception of a few hybrids.
- GERMINATION - Seed Needs packets contain some of the freshest seed available. Direct from the growers. If sown correctly, you will begin seeing results in only a matter of days.
- Pollinator Garden - Milkweed plant is the perfect plant to grow to have your very own butterfly garden. Also great for pollinators.
- VARIETIES - The 4 varieties included in this assortment is rose, butterfly, common and showy milkweed flower seeds for planting!
- SAVE THE BUTTERFLIES - Butterflies rely on certain plants. Monarch butterflies need milk weed to help them survive.
- BEAUTIFUL - Not only are milkweed plants helpful to butterflies and bees, they are beautiful plants, with showy flowers.
- PACKETS - Each milkweeds seeds packet is printed on water resistant paper, in full color with growing and harvesting directions included. Each heirloom flowers seeds packet contains at least 400mg of seeds.
- Monarch Butterfly - Common Milkweed (Asclepias syriaca) is the only food source for Monarch caterpillars, and grown Monarch butterflies love the plant as well. With declining Monarch populations in the US, these host plants help provide homes. Minimum of 400 mg per packet.
- Beautiful - Common Milkweed is a native to most US states. The beautiful native produces purple/pink clusters of flowers and is a favorite wildflower among gardeners.
- Pollinator Friendly -The nectar in Milkweed attracts many butterflies and bees. Milkweed also provides the necessary large leaves for caterpillars and nectar flowers for grown butterflies.
- Easy to Grow -- Instructions included on each packet with additional growing tips in the “How To” section of our website. Plus we are available to answer your questions as well. If these seed don’t germinate, we will happily make it “Right” for you.
- Safe Seed -- Sow Right Seeds has taken the Safe Seed Pledge and sells only Non-GMO heirloom seeds that are safe for you and your family.
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If you decide to plant the seedlings outdoors, choose an area where weeds do not grow or where there is minimal weed growth. Another aspect that you will have to keep in mind when you chose the area for swamp milkweed is to choose a place where there is ample soil moisture.
Place the swamp milkweed plants at a distance of 46 cm apart in order to allow them to spread as needed. After planting the seedling, don’t forget to lightly water them as when the plant is not fully developed, its roots may struggle to survive in extremely damp soil.
Also, make sure to constantly remove weeds that may steal nutrients from your plants. Although is a low-maintenance plant, it should not be planted next to highly competitive vegetation. If the plant vegetation around it is increased, swamp milkweed may struggle to compete as it is a slow-growing plant and will rarely produce flowers in its first year of growth.
Watering Swamp Milkweed
When it comes to watering swamp milkweed, remember to always keep the soil moist as it encourages optimal development and flowering each year. You will have to water these plants regularly to keep the soil moist, but pay attention not to overload the soil with water especially in the first year, when the roots are not fully developed.
One tip regarding watering and determining of moisture of your swamp milkweed plants, especially in the hot summer months, is checking if the leaves start to drop. If that happens, it means they are lacking moisture so, in this case, you can try to provide some afternoon shade for your plants. Another aspect that influences the frequency of watering, is how often it rains in the area where you live and also the time of the year as in the fall, spring and winter it may rain more than in the summer.
Propagating Swamp Milkweed
Gardeners will generally propagate swamp milkweed with seeds and this is a relatively simple process. To grow swamp milkweed from seeds, sow them in winter or put them in a cold moist stratification for 30 days. If you will create a cold environment for them and give them 30 days it will increase the germination rate.
The stages of propagating swamp milkweed from seed are the following: fill a pot or container with moist potting mix, plant between 3 to 5 seeds, cover them with soil, and place the container in a location that will receive morning and afternoon sun.
The germination will occur once the daytime temperatures rise above 21˚C. If you want to gather swamp milkweed seeds you will have to gather the pods immediately after begin to open up. Once the pods open, you can gather all the seeds which should be stored in a dry room. After they are fully dried, you can store the seeds for a couple of years in a sealed plastic container.
In most cases, swamp milkweed that grows from seeds should be established in the second year. In their first year, the young plants may produce a few smaller blooms if the soil is fertile and the seedling is more vigorous. But as a general rule, the plants will bloom in their second year.
If you are considering growing swamp milkweed in your garden, you will get to enjoy the fact that in the spring, summer and fall months this flowering plant will be visited by many insects including multi-coloured butterflies. By growing swamp milkweed in your garden, you will also help the monarch butterfly as milkweeds are their host plants.
So, if you decide to grow Asclepias incarnata a.k.a swamp milkweed in your outdoor area, you will enjoy a beautiful flower and host the monarch butterfly too. But at the same time, the plant will repel some species of unwanted guests as it contains latex.
Moreover, this plant will not only enhance the natural beauty of your garden, but it can also add a subtle vanilla fragrance and colour to your home with its soft pink flowers by using it as a cut flower. It is important to remember that swamp milkweed will thrive in full to partial sun and its ideal environment consists of wet to moist conditions and rich soil that contains rotting organic material. Swamp milkweed can tolerate occasional flooding as long as it is only a temporary situation, but it will not tolerate hot dry conditions.
Most gardeners agree that swamp milkweed is a low-maintenance plant and a great companion for many plants and flowers. As long as you grow this plant in a sunny location and provide it with plenty of moisture, it will reward you with fragrant blooms that will attract butterflies and other beneficial insects to your garden.
Are you growing swamp milkweed in your garden? Share your experience in the comments!
Swamp Milkweed FAQS
How invasive is swamp milkweed?
Swamp milkweed is not typically considered invasive. It is a native plant to many parts of North America and is a beneficial plant for monarch butterflies. While it can spread through seed and sometimes by rhizomes, its growth is generally not aggressive enough to label it as invasive in its native habitats.
Why is milkweed illegal?
In some areas, certain species of milkweed might be restricted or discouraged because they can be toxic to livestock when consumed in large quantities. However, it’s important to note that not all milkweed species are illegal everywhere. Many jurisdictions encourage the planting of milkweed, especially to support monarch butterfly populations. Always check local regulations before planting.
What’s the difference between swamp milkweed and regular milkweed?
The term “regular milkweed” often refers to common milkweed (Asclepias syriaca). Here are some differences between swamp milkweed (Asclepias incarnata) and common milkweed:
- Habitat: Swamp milkweed prefers wetter habitats like swamps and wet meadows, while common milkweed is more tolerant of dry conditions.
- Leaves: Swamp milkweed has narrow, lance-shaped leaves, while common milkweed has broader, oval leaves.
- Flowers: Swamp milkweed typically has pink to mauve flowers, while common milkweed has pinkish-purple to almost greenish flowers.
- Height: Both can reach similar heights, but swamp milkweed is generally a bit shorter, usually up to 4 feet, while common milkweed can grow up to 6 feet tall.
- Growth: Swamp milkweed is generally less aggressive in its growth habits compared to common milkweed, which can spread more readily through rhizomes.
How aggressive is swamp milkweed?
Swamp milkweed is not particularly aggressive. While it can spread by seeds and occasionally by its rhizomes, it does not spread as vigorously as some other milkweed species, like the common milkweed. In a garden setting, it’s generally easy to manage.