Which Native Milkweeds Are Best For Monarch Butterflies?
Monarch Butterflies need Milkweeds (Asclepias sp.), right? Because Monarchs lay their eggs on Milkweeds and only Milkweeds. But when it comes to attracting and supporting Monarchs, are some Milkweeds better than others?
Scientists from several universities have recently published some research on this very question. I became aware of this study thanks to Sue Dawson, who started the Facebook group Gardening with Nature in Mind.
The researchers tested 9 species of Milkweed over three years. All were native to the Midwest. Plots of each species were established at research farms operated by Iowa State University at different locations throughout the state. They recorded the number of eggs laid and the survival rate for the resulting caterpillars (larva).
Turns out the best Milkweeds overall are Swamp Milkweed (A. incarnata – also called Rose Milkweed) and Common Milkweed (A. syriaca), which scored high for both egg-laying and caterpillar survival. Gardeners tend to avoid Common Milkweed because it is pretty aggressive, but Swamp Milkweed can be found at many garden centers.
I was disappointed that Butterflyweed (A. tuberosa) scored low for number of eggs, though it does well with caterpillar survival. Butterflyweed is my favorite Milkweed for 3 reasons: its mounded habit, its tendency to gradually grow into large clumps instead of running all over the place, and (most of all) those incredible orange flowers.
It’s a funny thing, too, because I have plenty of Swamp Milkweed but have seen Monarch Caterpillars in our garden only on Butterflyweed.
For gardeners, it makes sense to plant a variety of Milkweeds. If at all possible, that variety should include Swamp Milkweed. Though it naturally grows in moist to wet soil, Swamp Milkweed does OK for me in fertile soil that has just medium moisture. In addition to Swamp Milkweed and Butterflyweed, we currently have Prairie Milkweed (A. sullivantii) in our garden – and I’m trying to establish some Poke Milkweed (A. exaltata) as well.
And I wouldn’t plant Common Milkweed unless you have a lot of space or are ready to engage in a long-term struggle against a ruthless expansionist. Another Milkweed to avoid is Honeyvine Milkweed (Cynanchum laeve), which can be a real pest and is not ornamental at all. Plus it does poorly at Monarch caterpillar survival.
If you want to read the article yourself, here’s a link.
Have you noticed if Monarchs prefer a particular Milkweed species in your garden?
I am familiar with milkweed from back east, but have not seen any growing wild in my area. I’ll be trying out the orange butterflyweed this year.
It’s a beauty, and does well in dryer soils.
I only have common milkweed here and there – so far it’s not toooo aggressive but I do pull up some of them each year. I’m so glad to hear that swamp milkweed was highly ranked – I planted several in the garden last year (grown from seed!) and am really looking forward to having them come up this year and, hopefully, put on some good growth. Butterflyweed is also on my list.
Swamp Milkweed is beautiful and it has a really nice vanilla fragrance.
Since the only milkweed I have been able to get established is the Asclepia that is what I have in my garden. I don’t have the full sun that these plants need. I have tried Swamp milkweed in places that flood in my garden but again not enough sun.
Where we do a lot of birding there are huge swathes of Swamp milkweed. I rarely see Monarchs on these plants. I have often wondered why. Maybe we aren’t there when they are.
Hard to say, I can’t explain it.
Weirdly, I haven’t had much luck with true native milkweed in my garden. I think it’s the shade and heavy soil that I garden in. I typically plant Tropical milkweed, A. curassavica. Not ideal, but at least the monarchs have something as they migrate through here in spring.
I know the Xerces Society discourages the Tropical Milkweed but I don’t know if that applies everywhere. You would be closer to its native range, I imagine.
In the three monarch waystations where i work swamp milkweed and butterfly weed do well. And, on my fourth attempt, the glorious purple milkweed (A purpurascens) reached maturity. However, as noted by Tina (above) it is the controversial tropical milkweed (A curassavica) that really draws the monarchs.
As a side note, I visited a garden in Kansas City several years ago, not far from the home of Monarch Watch in Lawrence, KS. When I asked the gardener about the prolific plantings of tropical milkweed literally covered in feasting monarchs, she described that milkweed as an energy bar for the butterflies on their way south.
Congratulations on the Purple Milkweed! All mine has died out, alas. I don’t know what to say about the Tropical Milkweed, I feel I ought to read up on it.
Here in southeast Texas, one of the best performers is A. perennis, sometimes called shore milkweed, and sometimes aquatic. Slim milkweed (A. linearis) does well, too. From what I’ve heard gardeners say, both establish fairly well. Sometimes, people will try to establish green antelope horn (A. viridis), which is one of our most common natives.
Several on the list are native to Texas, but aren’t found in my area. I’ve never seen swamp milkweed, for example.
Huh. All of those are new to me, except for the A. viridis.
I’m not sure that my shady yard would support any kind of milkweed, but I’ll look into it. A new year’s resolution for the garden.
Poke Milkweed will tolerate shade.
I will keep that in mind!
I have four varieties of milkweed here in MA – swamp, common, butterfly weed, and whorled. I’ve seen monarchs mostly nectaring on the swamp milkweed. I feel like the caterpillars prefer the common one, but I’ve seen them laying eggs on the swamp milkweed too. I haven’t seen them on the butterfly weed or whorled milkweed nearly as much, so same as the research!
Well, it’s good to have some affirmation.
The first yeas I planted a Butterfly weed I had a dozen Monarch catepillars on. Ditto the Honeyvine. it is a real pest in my flower beds.
That’s what I hear about the Honeyvine. I hear it is really hard to get rid of.
I have common milkweed in my yard, and yes, it will spread, but I have not had trouble controlling it. I haven’t had much luck growing other varieties, including butterflyweed. Also, doesn’t egg and caterpillar survival depend a lot on what predators one has in one’s yard?
Well, if the Common Milkweed is manageable that’s a plus. Do you have it in open fields or in your garden beds.
GREAT POST! There are several species of Milkweed here on the farm but I have not seen that many Monarch butterflies. Some years there are more than others. Believe it or not, last year was the first year I have seen their caterpillars. I always check the milkweeds hoping to find caterpillars. Thanks for sharing!
It took several years before I saw Monarch cats on my Milkweeds as well.
It is too bad butterfly weed isn’t as good, that’s what I have. I am trying to start some of the showy milkweed seeds though, and it looks like they’re pretty good. I have so many things planted for the butterflies, but I actually don’t get many. I get loads of different bees, but wonder where the butterflies are? I live a block from rural areas, so maybe they prefer that to the edge of the suburban streets!
I can’t live without butterflyweed, even if it isn’t tops for attracting Monarchs.
Butterfly weed doesn’t grow here naturally. From what I’ve seen the monarchs seem to like common milkweed, which we have a lot of.
In open fields, not in gardens, I assume.
Yes, I don’t see many in gardens.
Have lots of wild Common Milkweed at our WI place. Don’t have trouble with it spreading, but it is a messy plant. Thought about spreading some seeds here, but maybe I’ll try the swamp milkweed instead. Btw, the butterflies are going to love your zinnias!
I think you’re right. I would try the swamp milkweed first in your home garden.
Great summary! I already have common milkweed growing scattered across the property (and not being too much of a problem). I’ve been thinking of planting in the wetter areas, so will definitely be checking out swamp milkweed. Thanks!
The swamp milkweed is a sweet plant. There’s also a white cultivar called ‘Ice Ballet’, it’s not as tall.
By the way, not sure if you know that the link back to your blog doesn’t work.
I did read about that study, too. It’s interesting…most years, I’ve found many more eggs on Swamp than on Butterflyweed. But last year, I seemed to have a record number of eggs and caterpillars on the Butterflyweed. The study was conducted over three years, but I’m wondering if more years would show occasional shifts. I can’t seem to get Common Milkweed going here (too much shade and rabbits). I’ve tried to start it in a controlled area, but no luck. So I think it’s time to give up. I could grow it in my sunny garden, but then it would take over everything else! Thanks for sharing the highlights of the study.
Maybe changes in weather influences which plants they favor. Or there are other factors we aren’t even aware of.
This is great, reminds me of the butterfly bush we had in my family home growing up.
Butterfly bushes are great for attracting butterflies looking for nectar. They are not host plants, though – butterflies do not lay eggs on them, as far as I know.
We planted our first milkweed last summer, and haven’t noticed any butterflies anywhere near it. There are so many eucalyptus trees that they swarm to here. I will see what happens this year. It was not my choice. There is so much for the butterflies anyway. There is a native relative of the milkweed that the monarch butterflies leave their eggs on. I don’t know what is so special about the eucalyptus trees.
I read somewhere that there has been a big drop off in the number of West Coast Monarchs.
That is only because there was such a horrid proliferation of them for a while. When they migrated through San Jose, they stuck to anything, even roadways. They swarmed the blue and red gums on the central coast. Yet, through it all, they ignored the California poppy, which is relatively scarce in some regions.
Lucky you having these beauties.
Let’s hope everyone does enough to keep them from disappearing.
Elizabeth Roth left a comment in Gardening with Nature in Mind, saying she found the group through this article. Thank you, Jason! I have been spending so much time on Facebook, that I haven’t been keeping up with my blog or blog reading, so I am glad she posted that, so I could come find this post. I try to post for Gail’s Clay and Limestone Wildflower Wednesdays, but have let that slip the last few months. I hope to get one done in March.
When I first started the flower beds in our small SE Nebraska yard, common milkweed volunteered. It has not been aggressive over the years. I do pull a couple up from time to time so they won’t be crowded and get diseased, or if one pops up in a different area. Over the years I have planted whorled, showy, swamp, and I am thinking some kind of green that didn’t survive. I stopped planting tropical after finding out it can cause them to breed when they should be migrating.
Like Beth, I am curious about what the findings would be if they extended that study. I find differing amounts of monarch eggs and caterpillars on the different kinds from year to year. Sometimes there are lots on a few plants, but none on the same kinds that are near them, so I wonder why that is.
I have found eggs only on the Butterflyweed. It took several years before I found any eggs at all, but we are in a more urban area.
Just wanted to share my pics