Swamp Milkweed – How to Grow Asclepias Incarnata


Swamp Milkweed Bloom

Swamp Milkweed is a native perennial that grows to about 4’ tall and is very showy.  Similar to common milkweed in structure, it blooms slightly later which allows for a longer milkweed blooming season. 

Like other Asclepias, this is a larval host to the Monarch butterfly, and is pollinated by many other butterflies and bees as well. We’ve had at least 15 Monarch Caterpillars on a single plant in our micro-prairie.  It has gorgeous pink/white blooms that are long lasting (~ 1 month).

But if you would like to learn more about this plant, how to grow it from seed and care for it – then by all means read on!

Swamp Milkweed Facts

  • The name Asclepias is for the Ancient Greek God of medicine Asklepios
  • Native Americans used this and other types of milkweed as medicine for a variety of ailments
  • This milkweed is a ‘clay-buster’, as it can grow really well in heavy wet clay soil
  • This is a larval hose for Monarch Butterflies

Scientific Name

The Scientific Name of Swamp Milkweed is Asclepias Incarnata

General Description and growing conditions of Swamp Milkweed

Leaves and Stalk

Swamp milkweed is similar to common milkweed in that it has an un-branched stalk (except for flowering area) and opposite leaves.  The primary differences between Swamp Milkweed and Common milkweed is that Swamp Milkweed only spreads via seeds, not rhizomes. 

Also Swamp Milkweeds leaves are a bit smaller, being 2.5” – 6” long and a bit narrower, as well as coming to a point instead of being rounded.   I’ve noticed that the leaves of Swamp Milkweed turn a nice purple color in Fall.

Flower

Swamp Milkweed will produce several clusters (umbels) of ¼” flowers that are very detailed and intricate.

After blooming, pods will form at the base of the flowers that contain the seeds.  These pods will be several inches long by ½ inch wide.  Once the pods turn brown and have dried, they will begin to split open and release seeds to the wind. 

If you wish to harvest seeds, you can do so once the pods are brown you can collect the pods.  Another method of saving pods is to place a small rubber band around the pods while they are still green.  This will prevent pods from splitting open and releasing seeds.

We have a wonderful method for harvesting Milkweed seeds without making a mess. You should read it to save yourself some clean up time!

Pods are beginning to open on this plant.
Beautiful fall color on the leaves. (Flanked by Big Bluestem grass.)

Swamp Milkweed Growing Conditions

This plant needs full sun or partial sun and moist soil to thrive.  Partial sun generally will result in smaller plants with fewer flowers.  As hinted at by the name, this plant likes to have wet feet (moist soil).  Planting this on dry sites will be unlikely at having much success in survival.

I have 5 plants in our backyard prairie, and they are thriving.  This is a heavy clay soil, but stays fairly moist as it is at the end of a long slope.

Swamp Milkweed asclepias incarnata

Garden Uses

This is an ornamental plant that can grow where many others cannot.  That being said, planting it at the bottom of slopes or low spots will yield healthier plants.  I use mine in our microprairie, at the back of the slope, as the ground is moister in that particular location.

==>Learn how to make your own micro-prairie hereOpens in a new tab.<==

Micro Prairie

But, Swamp Milkweed is not invasive, so it can be planted as a specimen or clustered in borders or other areas.  Just remember, the more plants you have should mean better likelihood of attracting Monarch Butterflies.  Swamp Milkweed blooms for approximately 1 month, making it a longer-blooming perennial.

Swamp Milkweed is a great companion plant to other members of the Asclepias Family, such as Butterfly Weed.  Read about Butterfly Weed here ==> https://growitbuildit.com/asclepias-tuberosa-how-to-grow-buttefly-weed/Opens in a new tab.

Growing Swamp Milkweed From Seed

To grow Swamp Milkweed from seed, cold stratify in a moist paper towel in the refrigerator for 2 months, stored in a zip lock bag.  Alternatively, you could direct sow in the fall, or winter sow the seeds.  I generally winter sow, as that is the easiest if you are trying to get a set number of plants.

Swamp Milkweed Seedling
Swamp Milkweed Seedling

Sow the seeds directly onto the soil, lightly covering.  The seeds generally do better in a firm seedbed.  After germination, grow the plants until they are several inches tall then plant out into the garden.

We’ve written a detailed guide (with pictures) for all Milkweed Plants. Click below to read it!

As an aside, this plant has been found to have one of the highest seed production ratesOpens in a new tab. of all plants in the Milkweed family Asclepias.  So if you are able to locate a population, it should not be hard to collect an abundance of seed!

Purchase Seed

We have ordered a variety of native flower seeds from Everwilde Farms, which you can order right from Amazon through our link on our RECOMMENDED PRODUCTS PAGE. (We may earn a small commission when you purchase through our links, at no cost to you. This helps support our website.)

Video Overview

Below is a short video we made in our backyard micro prairie on Swamp Milkweed.  You can get some gardening ideas from seeing what we’ve done.

Have you been to our youtube channel?  You should check it out, as we post videos like these!

Faunal Associations of Swamp Milkweed

This plant attracts dozens of insects for pollination and feeding on the leaves.  Here are just a few examples of what you can expect to see if you grow a healthy population of Swamp Milkweed;

Disease Problems

This plant will get aphids, just like other milkweeds.  If infestation is severe, use a garden hose, and while holding the stalk with one hand use the garden hose to knock of the aphids.  Alternatively, you can use a soapy water mix to kill the aphids.  I personally don’t do anything to my plants, as the aphids will attract lady bugs eventually.

milkweed aphids on swamp milkweed asclepias incarnata
Note that these aphids appear to have attracted a predator! Go ladybug go!

Swamp Milkweed uses

Warning!  Swamp Milkweed is toxic in its raw form.  Unless you have been trained in the proper way to prepare young shoots, stalks, buds – don’t eat this plant.

Medicinal

Like common milkweed, Swamp Milkweed has been used for thousands of years by Native American tribes to treat various ailments.  Primarily they used the root to generate an infusion for treating ailments ranging from infant naval after birth, lung problems, etc.

Fibers

The fibers of Swamp Milkweed stalks can be used to make rope/cordage and woven into cloth.  As with Common Milkweed, wait until the stalks are brown/dry and can be broken off at the base.  Once dry, remove the outer layer by hand, then weave the fibers into a cloth.  Or, you can twist the fibers opposite to make rope.

Feather/parachute Uses

A really interesting use for Swamp Milkweed was that it helped the Allies win World War II!  The parachutes that are attached to each seed in the seed pods were used in World War Two to fill life jackets for the Allies.  This is because the feathery parachutes are much more buoyant than cork and other materials.  Additionally, the feathers can be used to stuff pillows, as they are quite soft.

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Joe Foster

Hi - I grew up outdoors in nature - hiking, fishing, hunting. In high school I got my first job at a garden center where I learned to garden and landscape. I've been growing plants from seed and designing native plant gardens for over six years. I hope to share some of my knowledge with you! Additionally I am a wood worker / DIY enthusiast. I enjoy designing/building projects (with hand tools when I can!). I hope to give you some tips and useful information!

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