Category Archives: Milkweed

Saving Swamp Milkweed

What I’ve found with Swamp Milkweed, Asclepias incarnata, in St. Louis MO is that it only lives for about three years, sometimes only two years in a typical home garden setting. While it prefers a wet-rain garden setting, all of my beds are raised for drainage and not ideal for this species.

One swamp milkweed that did spectacular last year, this year it now looks poorly and possibly dying. From my past experience I know that this plant will probably not make it next year. Here are a couple of pictures of the milkweed.



swamp-milkweed-dying-02What I’ve had success with in the past is cutting in back to six inches, digging up the root ball and separating it into individual plants. I will then keep them in pots for a month or two and make sure they are always moist. I then will plant it back in the garden.




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Milkweed Sources


Finding milkweed for the Monarchs can be a daunting task if you limit yourself to your local big-box stores.

Monarch Watch has put together a list of over 250 vendors. You can download the list at this link.

St. Louis Local Suppliers


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Asclepias curassavica – Tropical Milkweed


This particular milkweed has been the focal point of some recent controversy, so I thought I would put together as much research as I could find on this Monarch favorite.

Definition – Ophryocystis elektroscirrha (OE) is a protozoan parasite that infects Monarch and Queen butterflies.

Karen Oberhauser indicates that in Southern and Costal States + California – that OE can be a problem as the plants don’t die and OE can build up. Some sites advise to cut it down to the ground at the end of the season if you are in one of the warmer climates.

Thanks to Andy S. with this article from It again talks about the Southern State problem with OE and what can be done.

Here’s a recent TedTalk which seems to indicate that Curassaivica is good for Monarchs and is in fact medicinal against OE.

I emailed Chip Taylor, a well known expert in this field, about this video and this is his response.

“I haven’t had time to view the TED but here is my take from what I know about the issues.
There is a twist to the story – or interpretation. Monarchs surviving on A.c. having acquired an infestation of spores – are able to mate and pass on the spores to offspring since spores would be transferred to the new eggs or surrounding leaves. Monarchs receiving similar doses of O.e. spores but which have fed on other milkweeds would likely die – ending transmission to the next generation.
If you follow this, O.e. is a self-limiting disease (but you will never hear the researchers talking about it in these terms). Mortality/viability is dose related. Too much and you are dead, a little bit and you live to carry to spores to the next gen. A.c. allows more to survive and hence favors spore transmission.
That’s an issue in the south where A.c. overwinters (almost exclusively in gardens so the scale of the problem is quite limited) where O.e. can build up on leaves. It is less likely to be an issue in the north. Cutting back A.c. in the south at least twice a yr is recommended. It wouldn’t hurt to do that in the north if expecting to produce more than one gen on A.c.”
Dr. Jeffrey Glassberg, the President of NABA, North American Butterfly Association, wrote an article in the Winter 2014 issue of American Butterflies. Here’s the PDF. He says, “There is little evidence to support the idea that planting Tropical Milkweed will weaken Monarch populations and NO evidence to support the idea that Tropical Milkweeds are trapping Monarchs and stopping them from migrating to Mexico.

Here is a AskNature Article with the same information as the video.

Cardenolides per Species – interesting that Curassaivica has a very high percentage.

  • Asclepias curassavica – 1055
  • Asclepias syriaca – 50
  • Asclepias incarnata – 14
  • Asclepias tuberosa – 3
  • Asclepias verticillata – 1

San Antonio note – I got this email from a woman who lives in San Antonio. She said, “Monarchs are staying at the A. currasavica milkweed patch on the San Antonio Riverwalk all winter.” If you also look at the map below, you will see a lot of Monarchs do seem to stay in the southern states over the winter. Curassavica does seem to be stopping these Monarchs from migrating.


My summation –  it always makes sense to be aware of the OE problem and if in the South or California to take measures to limit use of Asclepias curassavica or at least cut it back a couple times a year. While only 8% of migrating Monarchs have OE, 85 % of the non-migrating Florida population have it. 

In Missouri – since tropical milkweed dies with the frost, spore transmission is not a problem.  What I have observed over the last 18 years is that even though I have a large tropical milkweed patch in October, as soon as we get a cool spell and the winds are moving in a southerly direction, the Monarchs take off on their migration.

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Winner – Asclepias Incarnata Soulmate


While I had poor germination with these seeds. probably because they were not cold-stratified, the one which did germinate in March is a winner now at the beginning of August. Most of my regular Asclepias incarnata looks terrible – almost as if it is dying and I don’t know the reason. Most people I know don’t have good luck with this so-called perennial in St. Louis. This particular variety looks spectacular the first year and I’m amazed that it’s blooming this first year. I’ll definitely keep these seeds for planting this fall.

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Monarchs – Back in St. Louis


I’ve finally had a female Monarch sighting in my garden and she was laying eggs. I saw about a dozen eggs laid, but there were probably more. If you look close at one picture, you will see all the aphids and white flies on the milkweed. I’m pretty sure they don’t have any impact on the larvae.

Instead of spreading my plants out, I put all my milkweed into one area to try and entice the Monarchs into my back yard. Most of the plants are tropical milkweed, but I also have incarnata and tuberosa.



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Common Milkweed Cuttings


Asclepias syriaca or Common Milkweed is a great plant to grow for Monarchs. While I don’t recommend it for most gardens since it is so invasive, I’m going to try and grow it this year in a large pot to keep it contained.

The problem is that no one in the St. Louis, MO area carries the plant. Even my main source for native plants, Missouri Wildflowers, had a crop failure this year and has no plants. I’m trying a second way to get some plants and that’s by cuttings.

I’ve got a friend with milkweed in her front yard, Yvonne, and she allowed me to come over and take some cuttings. I’ve got ten cuttings in plastic bags using rooting hormone and two cuttings I just stuck in a pot outside which is in some water to keep it well hydrated.

I’ll report later on the success/failure of both techniques.


REPORT – ZERO success!
I was both disappointed and surprised that none of my milkweed cuttings rooted.


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European Ideas for Swamp Milkweed



I was recently on vacation in Europe and found a couple of interesting gardening ideas which I thought I might try to add to my butterfly garden.

As you can see from the picture #1 – this gardener has raised beds which have a tendency to shed water instead of it soaking into the ground. She solved this by sinking a pot next to her tomato plant. Just fill up the pot and the water slowly goes into the soil.

In picture #2, they have sunk a large plastic container in the ground and as you can see it holds water more than the surrounding ground.

I’m going to try both of these ideas for my plants that prefer wet feet like swamp milkweed and Lobelia cardinalis.

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Monarch Butterflies Have Arrived in St. Louis


Yesterday, April 22nd, I saw my first weathered Monarch butterfly arrive in St. Louis. It went right past my 50 assorted milkweed plants, but I’m hoping it doubles back and lays some eggs. I think it was a female.

I also learned today that St. Louis has started a “Milkweeds for Monarchs – The St. Louis Butterfly Project.

St. Louis City is going to put in 50 Monarch gardens and is encouraging the community to plant 200 more.

While the effort is noble, they have a number of recommendations which need to be tempered with experience. They recommend a 3′ x 3′ area and suggest filling it with 9 different plants – 3 of which are invasive. A New England Aster can fill a 3′ x 3′ area by itself.


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How to Double Your Milkweed Plants


I brought in a few cuttings from my tropical milkweed, asclepias curassavica, last fall and later put them in pots. One easy way to double your number of plants is to cut them in two, and put the cuttings in a pot of their own.

The plants prefer wet conditions while rooting so keep everything moist. I like to keep water in my tray.

Make sure you wear gloves – the white sap is toxic and can cause blindness if you rub it in your eyes.

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Milkweed May Cause Temporary Blindness


I was reading Betty Hall’s blog about gardening and milkweed and ran across a great article about possible blindness problems with milkweed. Article 1Article 2

If you cut the milkweed, get the white sap on your hands, and then rub your eyes, it can apparently cause temporary blindness.


Since I cut a lot of milkweed to raise monarch caterpillars, it’s definitely something I need to be aware of in the future.

On thing I do which may mitigate the problem is that I almost always wear gloves. Glove will not only protect your hands, but also they are easy to take off if you have to rub your eyes.


I like to use the throwaway exam/medical gloves. I have a tendency to get my cuticles infected and so they provide protection to my hands and can be thrown away when they rip. I do reuse them when possible.

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