Meet the Natives: Swamp Milkweed

ESSENTIAL FOR MONARCH BUTTERFLIES, plants in the milkweed family are such important additions to the wildlife garden that I cannot imagine being without mine.

Shown above with a visiting monarch, swamp milkweed (Asclepias incarnata) grows about four feet tall and bears flat heads of pink flowers in summer or even into early fall. A cultivar called "Ice Ballet" has white flowers, while the cultivars "Cinderella" and "Soulmate" are varying shades of pink. The flowers are followed by attractive seed heads in the fall.

As the name implies, this milkweed is a lover of wet places, making it a perfect addition for any wetland (or just plain wet) garden. Mine is growing in a drainage area that also serves to draw water away from my house. The photo below shows the rock-filled drainage ditch leading away from this mini-wetland, which was just scooped out of our clay-filled soil. As you can see from the photo, the flowers attract hordes of butterflies, and not just monarchs. (These are fritillaries.) Swamp milkweed also attracts hummingbirds, hummingbird moths, and certain beetles.


Milkweeds are essential for monarch butterflies because plants in this family are the only ones monarch caterpillars will eat. The milkweeds contain toxic chemicals (warning: toxic to humans though apparently only in large quantities) that cause the caterpillars to taste bad. This protects them from predators.

In Canada, swamp milkweed is native in Manitoba, Quebec, and Nova Scotia; in the United States, it is native to the Northeast; as far south as Georgia, Texas, and Louisiana; and as far west as North Dakota.

Plant swamp milkweed in a moist spot; heavy soil and/or occasional standing water are not a problem. The site should probably receive full sun, though some sources say that this plant can tolerate part shade. Because it has a long taproot, don't plan to move it after you've planted it. Swamp milkweed will spread slowly by rhizomes, and you can naturalize it by scattering the seeds.

The plant is said to attract aphids, but it's highly unlikely that these insects will kill the plant. If aphids gross you out, try to remember that birds take a different view--"bird ice cream," I call them--and will most likely control any aphid outbreak for you. If deer are a problem in your neighborhood, you'll be happy to hear that they don't like the taste of milkweeds.

For more information on milkweeds, I highly recommend the 10,000 Birds blog entry for July 20, 2007. Ten Thousand Birds is a great blog to follow if you're interested in birds, especially if you're a bird watcher.

For additional information on swamp milkweed specifically, check out "This Week at Hilton Pond" for July 15-21, 2001. While you're there, I hope you'll look around this website. The Hilton Pond Center for Piedmont Natural History sure sounds like a place I'd like to visit. The Lady Bird Johnson Wildflower Center also has good information on swamp milkweed.

15 comments:

Corey said...

Nice informative post! And thanks for the link.

Wild Flora said...

Thanks, Corey. It's a pleasure to recommend your site.

julie said...

Thanks for all of the great milkweed info. Anyone interested in learning more about milkweed's most admired "customer," the monarchs, may want to start visiting Journey North's monarch migration site (http://www.learner.org/jnorth/tm/monarch/AboutFall.html). It's a citizen science site where you can enter data from your own observations and follow migration sitings from throughout North America as monarchs make their way to overwintering destinations in California and Mexico.

Wild Flora said...

Great tip, Julie. Thanks!

jodi said...

Good to see you back blogging, Wild Flora. (I've been insanely busy too, so I can understand the 'vacation'. Glad also to see you profiling one of my favourite plants (and our monarchs too!) I have to say I've never seen aphids on our swamp milkweeds, but maybe the birds and ladybird beetle larvae take care of them.

The chrysalids aren't hatched yet--I'm expecting any day now to see them opening and the monarchs emerging.

I have an email somewhere in my computer (which had a tantrum several weeks ago) from you about A. syriaca and how the doughheads in the NS goverment still list it as noxious. I think we ought to all get our heads together and do something about that.

Wild Flora said...

Hi Jodi,
One of the reasons I had to come back to blogging is that I missed hearing from people like you and Julie. I haven't seen aphids on my swamp milkweed either, but so many of the articles I looked at mentioned the aphid angle that I thought I had to mention it. I also think it's time something was done to change noxious weed laws that ban milkweeds. One idea I've been mulling is to try to start some sort of blogging meme on the topic. In the meantime, I'm collecting information on noxious weed laws and how they affect milkweeds and monarchs, and I also want to double check to make sure that these laws really still are on the books. (It's just so hard for me to believe anyone would do such a thing!) Within the next week, I should have something to post here on the blog.

Puddock said...

Hi Flora

Thanks for visiting my blog. I love your pic of monarch butterflies. We don't get them here in Scotland. We do get Peacock butterflies though, which are probably our most spectacular butterflies. Love the blog!

Wild Flora said...
This comment has been removed by the author.
Wild Flora said...

Our first visitor from the British Isles! And from the land of my ancestor (grandmother), as well. What a treat. Hi, Puddock, and thanks for stopping in. I've never heard of Peacock butterflies and will have to look them up.

Puddock said...

I took some pics of Peacock butterflies in the garden today. I'll put them up on my blog tomorrow. They are lovely, they have large eye patterns on their wings, like the eyes on a peacock's tail.

Wild Flora said...

Way cool, Puddock. Thanks!

Craig & Sara said...

Can you tell me where to get Milkweed to add to our yard? I haven't seen much online about native NW plants to purchase. Thanks!

Wild Flora said...

Dear Craig and Sara,
Usually a good place to get leads on where to purchase native plants is through your local native plant society. There is a good list of state and provincial native plant societies at the website of the Michigan Botanical Club, http://www.michbotclub.org/links/native_plant_society.htm

Anonymous said...

Hi Flora! I allow milkweed to grow in my garden. I do keep it "thinned" out so that it doesn't take over the other perennials though. We usually have two or three Monarchs in our garden, every year, however to date I haven't seen any. Only a few swallow tails. Milkweed smells beautiful. It came here itself, I did not plant it, nature did, so if the town I live in wants to fine me, good for them, they obviously have nothing better to do with the tax money I pay them! Anita from Ontario

Wild Flora said...

Hi Anonymous Anita from Ontario,

According to another post I wrote on this topic, as of 1996 the province of Ontario only tried to control milkweed on a "complaint" basis, so as long as you're on good terms with your neighbors and/or nobody can see the milkweed, you're fine. My philosophy is that homeowners in less rural areas should be encouraged to keep and plant milkweed for Monarchs, of course. This would help to offset the harm done when milkweed is kept out of agricultural areas.

F