How do I permanently kill native milkweed?

grandmothers_rose(z6b VA)April 28, 2012

I planted native milkweed three years ago for the Monarchs. The Monarchs all, as in every single one, had OE so, last fall after two years of growth I decided to dig up the milkweed. This spring I have dug up shoots no less than four times, removing as much of the root as I could follow in the soil. I can tell the next time it pops up will be too near my perennials to dig up. What can I spray on the milkweed to kill it? Regular Round-Up sprayed twice on consecutive days did not phase it the least.

I truly understand the phrase "noxious weed" which is also used to describe native milkweed. I hope this post serves as a warning to other uninformed people who are considering planting it. In my opinion, native milkweed should never be recommended without a dire warning in the same sentence.

I also grow butterflyweed, tropical milkweed and swamp milkweed that appear to be ok.

Thank you for reporting this comment. Undo
terrene(5b MA)

Do you mean Asclepias syriaca - common milkweed - when you say native milkweed? Because there are over 100 species of milkweed that are native to North America.

Anyway, I think you might be posting on the wrong forum here. No offense, it seems odd to come to a butterfly forum asking about eradicating a native host plant that is critical for one our most beloved species. On top of that, the native milkweeds are under attack by herbicides on a mass scale, due to GMO food crops and blanket applications of glyphosate.

That said, if your desire is to have a garden that is formal and "under control", Asclepias syriaca and some of the other milkweeds that spread by runners do not make good garden plants. I would just keep pulling or clipping it, it will die off. Repeated roadside mowing also manages to eliminate some of the native milkweeds too.

    Bookmark   April 28, 2012 at 9:59AM
Thank you for reporting this comment. Undo
grandmothers_rose(z6b VA)

It is Asclepias syriaca. Pictures in my Weeds of the Northeast book look just like it.

Terrene, please forgive my rant, it's not directed at you and I appreciate that you confirmed the method to eradicate it.

I posted here because I planted it on the advice of numerous posts saying it was a good host for the Monarchs (which it was.) Some people did say it could get out of control, but I didn't know it would grow from roots thinner than a pencil 6 feet away from the mother plant 6 months after the mother plant was dug up. Even mint is easier to eradicate in my garden!! I went out for the fifth time this morning to dig up more rhizomes. I am doubly frustrated because of its persistence and because all the Monarchs had OE. If the Monarchs had been healthy I could have dealt with the milkweed issue better. I dare say I'm a bit bent out of shape because the rhizomes are in my rose garden, now, instead of the annual part.

The weed book says to keep mowing it, too. So I'll continue to dig where I can and just break off the shoots when they sprout.

I will plant more of the tropical milkweed this year. I know it will die over the winter! Does it have any bad garden habits? Self seeding is fine, I just can't take the persistent roots.

    Bookmark   April 28, 2012 at 12:35PM
Thank you for reporting this comment. Undo
runmede(7a Virginia)

Our winters are cold enough to kill the OE. I'm 7A and looks like you are 6A. The common milkweed dies to the ground and comes up every year. Just cut the dead tops off in late fall and the shoots that come up in the spring will be OE free.

All milkweeds will eventually get OE because it is carried by the butterflies. It is more prevalent in the fall. I wash my milkweed in tap water (my water is chlorinated). Then I dry it off and feed it to the caterpillars.

I wish that I had time to hot link all these links. Just copy the url and put into your search engine.
Have you looked through this?
How to tell if butterflies are infected with OE

An infected pupa may develop dark spots or blotches two or three days before the butterfly emerges. These abnormal dark areas are parasite spores. Spores form on the eyes, antennae, wing veins, but mostly on the abdomen. You can see the spores through the outside layer of the pupa a day or two before pigments that color the butterfly normally darken the pupa. Before a butterfly emerges from the chrysalis, pigments are laid down coloring the scales that cover the butterfly. This normal change in the color of the pupa is symmetrical. The color change of an infected monarch happens earlier and does not create a balanced pattern on the pupa.

Here is a link that might be useful: My Monarch Guide Dreaded OE Spore

    Bookmark   April 28, 2012 at 2:08PM
Thank you for reporting this comment. Undo
grandmothers_rose(z6b VA)

Thanks for the websites!

Yeah. I did some research on the web and posted a few things here, too. Really, every single cat had OE. Many just died as cats, even in the "J" position, all chrysalises I found never hatched, all the cats were dull colored from the OE and it was worse at the end of the summer. Looked just like the photos on the web. All the bitty cats I took inside pupated but couldn't fly, and were still on the butterfly weed the next day. OE must be really bad around here (Shenandoah Valley.) The worst part is I had lots of cats, 50 or so.

I saw one website that suggested carefully cleaning the eggs to remove the spores. I might try that this year if I find any eggs. I bookmarked it. I'll have to bleach/clean the milkweed, too. The info on cleaning the eggs is at the end of the website.

I'll keep the butterfly weed and a couple tropical milkweed plants one more year. But the native, common milkweed has to go.

Here is a link that might be useful: how to clean Monarch eggs

    Bookmark   April 28, 2012 at 7:50PM
Thank you for reporting this comment. Undo
terrene(5b MA)

Grandmothers, I apologize if I came on a little strong, it was actually a little startling to read your post at first. In my yard and gardens, Asclepias syriaca pretty much grows where it wants, even in the middle of one of my woodland gardens in mostly shade! 2 years ago I "thought" I transplanted all of it out of that garden and to another spot - well that didn't work too well, it still came up as strong as ever, and is slow to establish in the new spot. Now I just leave it be and garden around it, because every year a few Monarch females find these plants and lay eggs on them and they make good food for the cats.

Some of the milkweeds including A. syriaca appear to have the ability to sprout from sections of root that are left behind in the soil. It also pops up a few inches or feet over from where it was the previous year. So don't be surprised if it pops up now and then even after you've removed most of it. It's a plant for wilder areas but IMO it should be safeguarded for the Monarchs.

Butterfly weed, tropical, and swamp milkweeds are much better behaved and stay put where you plant them! :)

A pic of a female laying eggs on the common milkweed in the woodland garden, where it's growing amongst the violets, Lunaria, and woodland phlox -

    Bookmark   April 29, 2012 at 9:06AM
Thank you for reporting this comment. Undo
grandmothers_rose(z6b VA)

Terrene, I still have some seeds (stored in the fridge) that I used to grow my milkweed. Want some? They grow into super vigorous plants! ;)

Or maybe it is the cow manure compost that the milkweed likes so well . . .

    Bookmark   April 29, 2012 at 1:07PM
Thank you for reporting this comment. Undo
terrene(5b MA)

Thanks grandma, but I've got plenty of A. syriaca seeds. I collect it from wild patches around here and scatter seed and share seed on the Seed Exchange. I keep a mental log of significant patches around here, because I use wild sources of milkweed as supplemental food for the cats as well places I can collect eggs and larvae!! :)

    Bookmark   April 29, 2012 at 4:33PM
Thank you for reporting this comment. Undo

Is there anyone willing to give me or sell me some different types of milkweed seeds? Thanx

    Bookmark   April 29, 2012 at 9:57PM
Thank you for reporting this comment. Undo
grandmothers_rose(z6b VA)

I have some of the INVASIVE common milkweed and some tropical milkweed. You should be able to e-mail me through gardenweb and I'll mail some to you. I didn't have any trouble sprouting either one and the common milkweed has been in my fridge (already cold stratified) so long it should sprout the minute you put it in some dirt. Thre are some really good instructions on the web for sprouting milkweed.

Here is a link that might be useful: how to sprout milkweed seeds

    Bookmark   April 30, 2012 at 7:42AM
Thank you for reporting this comment. Undo

Is there anyone that I can get some milkweed seeds from? I would love different kinds and colors!!! If anyone willing to sell or give seeds please email

    Bookmark   May 4, 2012 at 7:07PM
Thank you for reporting this comment. Undo


Have you tried the GW Seed Exchange? There are MANY users there who would LOVE to trade seeds with you.

Don't forget to read the Special Instructions for the Seed Exchange, first. If you have any questions just ask! Gardenwebbers are really helpful people.


Here is a link that might be useful: GW Seed Exchange Forum

    Bookmark   May 5, 2012 at 3:56PM
Thank you for reporting this comment. Undo

I have common milkweed throughout our small suburban garden. It does spread and when I need to trim it, I do. I find the monarchs really like the tender shoots anyway. I love the smell when it blooms and I have had my only sighting of a banded hairstreak on the bloom!

    Bookmark   May 9, 2012 at 2:12PM
Thank you for reporting this comment. Undo
runmede(7a Virginia)

Don't just blame the milkweed. It may be your containers. Those need to be bleached too. This year I ended up putting some bleach into my washing machine and turning off the wash cycle. Make sure you use cold water. Hot water will kill the bleach. I put my containers in there to bleach them. Then, I rinsed them in the large tub near the washing machine with hot water. Then, further washed with them with dish washing detergent. Then, rinsed them again with hot water. Then, some cold water. You need to make sure you get all the bleach and soap off. Those will kill the caterpillars, too. I'm in Herndon, VA. Probably about an hour from the mountains.

    Bookmark   May 9, 2012 at 11:34PM
Thank you for reporting this comment. Undo
terrene(5b MA)

Drsonja, feel free to check out my exchange page below and send an email if you want milkweed seeds. I have seeds for several species of Asclepias that you can get by doing a SASBE/BEAP (self addressed stamped bubble or bubble envie and postage). Instructions are on page.

Here is a link that might be useful: terrene's exchange page

    Bookmark   May 10, 2012 at 3:37AM
Thank you for reporting this comment. Undo
jazzygardener(z4 MN)

Milkweed is the only plant that the monarch butterfly will lay her eggs on. I have it planted in my garden and I encourage my neighbors to do the same. If you want to keep it from spreading dig a drench around the area that you have it planted and sink that heavy black plastic landscape edging at the root depth. This will keep the roots from spreading.

    Bookmark   May 17, 2012 at 1:19PM
Thank you for reporting this comment. Undo

Round-Up will kill butterflies. Monarch Watch or the National Butterfly Association, can't remember which, recommends using vinegar to kill your weeds.

    Bookmark   May 21, 2012 at 12:09PM
Thank you for reporting this comment. Undo

I hope it isn't rude of me to resurrect a thread from a few years ago, but I came across this thread while searching for information on controlling asclepias syriaca, more specifically, whether the rhizomes can be contained so as to prevent them from taking over (the seeds I'm not as concerned about).

I have a couple of 1 year old syriacas in my garden (planted last year), as well as some new syriaca and purpurascens seedlings I have started indoors. I'm just now realizing/reading about how aggressive established syriaca can be. I have been fighting ongoing battles with Japanese knotweed and bindweed in my garden, which makes me very leery of inviting more rhizome-related trouble! I also have a fairly small garden, which means that if the syriaca begins spreading, it will quickly be popping up in my raised veggie beds on the one side, or in my rose/perennial beds on the other side.

That said, is there a way to contain the syriaca rhizomes? Jazzygardener, above, mentions black plastic landscape edging--do others recommend this approach? Perhaps I'm overly cautious because of my J. knotweed experiences--those roots spread far too deeply underground for some black plastic to do much good, but J. knotweed is somewhat notorious for that so it may not apply to syriaca. If black plastic would work, what about large nursery pots sunk into the ground?

Or alternatively, might it be a better idea for me to focus on better-behaved asclepias that would be more manageable? As mentioned, I do have some purpurascens seedlings and from my reading, it looks like there are many other asclepias varieties that are better behaved. I don't want to do the butterflies any disservice, but I don't know if I can take on another garden battle! What would you recommend?

Thanks all for any thoughts and opinions. :)

    Bookmark   March 26, 2014 at 11:19AM
Thank you for reporting this comment. Undo
runmede(7a Virginia)

Asclepias incarnata (swamp milkweed) clumps and does not run.

You can plant tropicals so that you will have some food this year. In 7b, you would not have a problem with them being invasive.

I saw someone put down some plastic landscaping edging around the stand of milkweed and the common milkweed clumped instead of running around everywhere.

    Bookmark   March 26, 2014 at 2:43PM
Sign Up to comment
More Discussions
Journey of the Butterly
PBS stations are repeating The Incredible Jouney of...
Aristolochia Elegans Seeds for SASE
I have harvested a ton of seed pods (at least 45 pods!)...
Help for monarchs?
US Fish and Wildlife is spending some money to save...
socalgal_gw Zone USDA 10b Sunset 24
Coral Honeysuckle
I remember reading that Coral Honeysuckle is a good...
looking for mistletoe
Would love to attract a purple hairstreak .... any...
Meredith Mays
Sponsored Products
Sea Gull Lighting Outdoor Lighting. Cape May Wall-Mount 1-Light Outdoor Burled I
Home Depot
MR16 Square 3 Light Track Kit by SATCO Lighting
$83.85 | Lumens
Missoni Home | Mekele Vivid Pillow 32x32
Mighty Purse Poppy Pink Phone Charging Clutch
Classic Hostess
Classic Wicker Round Outdoor Dining Table, Patio Furniture
Sandstone 9-Inch Wall Sconce with Sea Turtle Cutout Design
$151.20 | Bellacor
People viewed this after searching for:
© 2015 Houzz Inc. Houzz® The new way to design your home™