How to Cold Stratify and Grow Milkweed Seeds (2024)

Asclepias incarnata stratifying in a cold/moist chamber at the Nebraska Statewide Arboretum. Photo by Rebecca Chandler.

Most of my Milkweed has been Common Milkweed. Put it in refrigerator dry, and did nothing else. Will try wet next time. Does it make any difference what temp it is held at ? currently have some in freezer.
Let one Monarch go two days ago. Still have 4 in Chryslis. Will make 2018
number around 30 Monarch's. Plan to tag them in 2019. Currently starting Tropical milkweed for next spring and plant as many stalks as I can find room for. Best milkweed because of flowers and it can sustain a large number of cats. Like your website. Cooper

Hi Stephen,
Thank you for your questions! I have had the most luck with the moist/cold method of stratification rather than the dry/cold method. The moisture helps to soften the seed coat so that the sprout can emerge. Freezer may work but it might also make the seed less viable over the period of 30-60 days. The ideal temperature is between 33–38°F. Best of luck!

If normally the seeds fall and overwinter in zones 3-5 where it was 25 degrees below 0 last winter, how is it possible they need to be kept 33-38 degrees to for just a month or two germinate? There are no Midwest winters with those weather conditions.

I heard from a Park Ranger that you should only plant milkweed indigenous to your area. And he specifically said that people are planting tropical milkweed because it's prettier, but it confuses the butterflies. They think they are much farther south and they stay in the area too long and freeze to death. Just passing on information, not judging. I never would have known and totally would've planted the more attractive plant!!

I plant about 6 or 7 varieties of milkweed and have found that monarchs in the fall are drawn more to the Tropical Milkweed over everything else. I've heard people say that if the tropical variety is left to stand that more OE can accumulate on it and it can be detrimental to Monarchs. In Oklahoma it dies back to the ground and I just pull up the old plants after I harvest the viable seed pods. This past year I tried to feed Butterfly Weed to my cats and they didn't want it so I went back to the Tropical. The flowers look like they hold up better and so does the foliage so perhaps that's why Monarchs prefer it. I'm not really sure. I haven't had any problem with Monarchs being confused and not knowing when to migrate -- I doubt that has any effect on them. I think the main thing is to provide a variety of milkweed so the butterflies have want they want and need during all times of the year.

It only applies to those that live where the milkweed grows into the fall. You don’t want monarchs stopping to bread when they should be going south. I was told to cut my tropical milkweed down in the fall to keep the monarchs from stopping. I forgot to last year and we did see a few monarchs that didn’t hatch or getting moving south fast enough. I won’t forget this fall.

I have stratified with the refrigerator method about 1,000 seeds, but I collected so many last fall I still have another 10,000 (i don't know the real number, but it's a big bag). Can I just put the seeds out on the snow in February?

Dan,
WOW, that is great!! You can absolutely just stratify them the "all natural" way if you have the space. Another option is to distribute them to folks in your community or set up a 'seed swap' event. You can also donate viable seeds to
Save Our Monarchs Foundation
P.O. Box #390135
Minneapolis, MN 55439
and we will distribute them in our School Pollinator Program.
Thank you for helping the Monarchs!

Recently I wrote to someone regarding extra Common Milkweed seed pods I have. What I do is to save the seeds in the fall just as the pods begin to open. There are many more than I can use so if anybody wants some, let me know directly or on CHAT. I do not charge for doing this and all I need is the mailing address of those that would like some.

I love to plant more Milkweed of different types. Do you still have some seeds ? Would it be possible to send me some? I really would appreciate it so much.
Helga Cotton
185 Yellowwood Drive
Sharpsburg, Ga 30277

Would you send me some seed please and thank you:
Lora Ost
32 Parsonage Rd,
McHenry, MS. 39561

Hi all! If any one has any extra Milkweeds seeds could you please send to me, I’d appreciate it!
Lyn Dominguez
10418 Carmen Lane
Royal Palm Beach FL 33411

It’s really important that you plant native milkweed to your specific area. So in Florida it would not be a good idea to plant milkweed that is native to Wisconsin or something like that. It’s best to do a search to see what milkweed is native to your specific area.

Do you have any leftover seeds for a Scout project? We are in Silver Spring

Great website and great tips on cold stratification for asclepias!! I am giving stratification my first try this week. After I cold stratify can I just plant them outside after average last killing frost? Or will the birds get them? Are indoor pots safer to sprout them then transplant? I have 8 weeks until avg last killing frost here in NW Arkansas. Thanks !!

Hi Alan,
Thanks for reading and best of luck with your milkweed! Yes, you would want to plant them outdoors after the last average frost in your area. However, I do prefer to start them indoors (after stratifying them) and then transplant them outdoors when they have reached a few inches tall. That way, I know that I am giving them every advantage of surviving and so they are larger so they can feed more caterpillars once the monarchs arrive. However, both of these methods will work. If you would like to read more on growing milkweed indoors check out my other blog: https://www.saveourmonarchs.org/blog/5-steps-to-planting-milkweed-seeds

Hi. If you plan to plant an acre or two you should get ahold of Dick Seng. The gentleman 2 posts above yours. He says that anyone that wants free seed pods full of seeds to get ahold of him and he will mail some to you.

Hi Eli,
Putting dry milkweed seeds (also called dry, cold stratification) improves the germination rate minimally. I did an experiment where I tried dry, cold and wet, cold stratification methods on the same types of milkweed seeds and the wet, cold seeds did significantly better than the dry, cold ones.
You can either plant them outside after your last average frost in your area or start them indoors under a grow light (my preferred method). You can read more here: https://www.saveourmonarchs.org/blog/5-steps-to-planting-milkweed-seeds
We sell milkweed seeds in bulk here: https://www.saveourmonarchs.org/store/c12/Bulk_Seeds.html

Hello I'd like to purchase milkweed seeds in bulk. Thanks!

I grew up in MN with the monarchs, but now live in desert AZ. Do monarchs fly thru here on their migration? I have never seen any. (Surprised to see a robin once🙂.) Someone sent me some wild milkweed seeds and I will try growing them. I will try the tropical ones if they don't survive here. Wish me luck.

Hi Jenny,
You can view the Migration Maps at Journeynorth.org to see if monarchs fly through your area on their migration. You can also find out what species of milkweed grow in your area at https://www.growmilkweedplants.com/map.html. Best of luck!

Update, saw a beat-up monarch in my garden over the fall. Poor thing. Bought some showy tropical milkweed seeds to plant in the spring. Also native varieties. Will be prepared next time one passes thru.

Hi Jenny,
Thanks for your questions! You can track the monarch migrations and see real-time maps of their migration at https://maps.journeynorth.org/maps Thanks!

Send info

I put a bunch of swamp milkweed seeds in a ziplock bag without a wet towel and stuck in my fridge probably 3-4 months ago. Obviously, not what I should have done, according to what I'm reading now. Do you think they are salvageable?

I did the same as you, and then planted them and mine are sprouting nicely.

They will be fine. As long as they've been in the fridge for 6-8 weeks, we've noticed that by keeping them in a zip lock bag with some wet sand for a week or two before planting them they'll germinate even faster.

I have had both showy milkweed and tuberosa seeds in fridge for just about a month, but they havent done anything save for some of the tuberosa seeds splitting apart..are they supposed to sprout before planting? If not, is it ok to just put them in pots and under grow light before last frost then plant in containers outside? (I'm in an apartment so cant put in ground.)

Go ahead and start them indoor under the light. keep in mind that the best way to grow milkweed with no effort is by fall-winter sowing:
www.savethemonarchbutterfly.ca/Grow-Milkweed-Plants-For-Pennies.pdf

Hi Dani,
No, the seeds are not necessarily supposed to sprout in the fridge. If they have started to sprout, that is okay but you will want to put them into soil immediately. If it isn't warm enough yet in your region, you can start them indoors in a sunny window or under a grow light.
The purpose of the cold stratification period is just to awaken them and let them know that Spring is near. In nature, they would go through a natural stratification period (winter) and know that spring has arrived when it starts to warm up. They would not start sprouting when it is still cold because it would lessen their chances of survival. I hope that helped! Best of luck.

Hello, I just pulled out a bag of milkweed pods (uncertain of the type) my son and I collected in Bethesda, MD last fall. It's now the end of April. Is it too late to cold stratify and plant the seeds? Also, we have a lot of seeds. Can we sow directly into the soil now and/or plant in seed trays without cold stratifying? This is our first time collecting milkweed pods to plant-- next year we'll know to cold stratify. Thank you!

Go ahead and cold stratify them, you're still in time to plant this year.
As for next year you should consider fall-winter sowing for less effort.
This link will show you how:
www.savethemonarchbutterfly.ca/Grow-Milkweed-Plants-For-Pennies.pdf

Sure fire way to sprout seeds indoors is to clip off the point of each seed with a nail clipper( yes, tedious).
Place the seeds in a container and cover with 1” non- chlorinated water. Put in a warm spot ( I kept mine in microwave with door ajar/ light on -about 80 degrees). Change the water ever 12 hours for 7 days. They will sprout!
I planted in small peat pots and kept moist and warm in a sunny window with lights on them during the day. When 2-3” high, hardened them off over a week 1hr first day working up to 7 hrs in a week.

I am in Delaware and it’s early June. I just got seeds but if a stratify them it will be July. Is it too hot in July to plant the seeds? Should I just wait a couple months? This is new to me.
Thanks!

Try this Alan and good luck! :-)
http://savethemonarchbutterfly.ca/Growing-Milkweed-Seeds-Year-Around.pdf

I would like to contact Dick Seng to get seed pods. How do I find him? I am very much interested in planting as much milkweed as possible in my area. Thank you kindly

Yes, I too would like to get the contact information for Dick Seng

About how long does it take for sprouted seeds to be ready to transition to the garden?

I usually wait for the plant to be at least 5-6 inches tall. ( Providing the weather is warm)

It takes at least a month for them to be large enough to be transplanted. I also recommend a "hardening off" period (gradually transitioning them outdoors) before you put them in the ground. Best of luck!

Do I use the same stratification & planting for Asclepias Purpurascens seed as the other MW?

Yes, you can use the same methods with Asclepias purpurascens .Thanks!

I live in San Antonio, TX and just received butterfly weed seeds from a friend. Is it ok to plant them right now and put in pots so the plants can be portable during cold weather days?

Yes,I'm not sure I understand your question. You can cold stratify them naturally by putting them in soil and leaving them outdoors during the winter. I have found the the cold/wet stratification period works very well because in the winter, they are usually under a blanket of snow that keeps their seed coats moist.
If you mean, can you start them indoors and grow them throughout the winter, that is also an option. However, because milkweed has a very long taproot, sometimes it makes it difficult to transplant them once they have gotten to a large size. Hope this helps! Best of luck.

Hello, any tips on planting outside when they've sprouted?

Hi Stacy,
More info on your question are available here:
http://www.savethemonarchbutterfly.ca/Grow-Milkweed-Plants-For-Pennies.pdf

If you want them by mail follow this page for more details:
http://savethemonarchbutterfly.ca/Free-Milkweed-Seeds-For-All-2021.pdf
See which native plants grow better in your area:
https://www.monarchmilkweedhabitat.com

Hi! Thank you for this article. What kind of soil should I use to start the seeds indoors, please? Is regular potting soil OK?

Always use good top soil to germinate milkweed seeds. :-)

Thank you, Leo!

This is my first attempt at growing milkweeds. I bought several varieties of milkweed seeds and have the seeds in the fridge following your stratification directions. I have seeds left over. Can I hold these over for next year? Can I put them in the freezer like I do with veggie seeds? Thanks.

I've had mine in wet sand in the fridge ( not freezer) for 4 years and they germinate like crazy when plant it. :-)
http://savethemonarchbutterfly.ca/Fall-Spring-Milkweed-Sowing.pdf

I started growing milkweed 4 seasons ago. I keep all my seeds, several types, that I don’t plant in the freezer. Most of my seeds germinate. I put some seeds in clear plastic containers and put out side and I start some indoors both wet & dry cold stratification. Best to sow seeds in fall, Mother Nature been doing it that way for a long time.

It's the start of April in Massachusetts and I have just collected a ton of common milkweed seeds that overwintered in fields. Should I just put them in the ground where I want them or germinate them first then put them in the ground. I assume the winter has already stratified them. Thanks.

You can do it both ways, most of us prefer the germination in outdoor small pots and transplant when they are 5-6" high.

Kristin, You did good with your tuberosa, my advice would be to put them into one or two gallon pots right away for more growth during August. By late fall cut the plants to the ground and keep them into the pots, in order to survive our freezing-thaw cycle of our winter you need to keep them repaired from the elements always outdoor in the cold like a shed, covered patio etc... ( make sure you water them once in awhile) Next spring summer you'll have some nice two years old plants. They are late coming up in the spring, to speed up the process bring some plants in the garage by early March. :-)
This is what I do with all my potted perennials and always come back. This was our last year backyard:https://www.photo-pick.com/online/fe0Z5BzL.link

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I purchased Common Milkweed seeds Native to N.H. Very excited to do more to help the Monarch butterfly’s. The instructions are not clear enough. States full sun, Stratify for a minimum of 4 weeks in refrigerator, which I understand how to do with dampened paper towels, what I’m unclear on is when to plant the seeds? A month from now after stratifying? In the spring once frost danger is over? Or when do I plant sprouted seedlings in New Hampshire?

Jennifer, I do have a page that has all that info:
http://savethemonarchbutterfly.ca/milkweed-general-info.pdf

Great Article! Thank you for sharing this very informative post, and looking forward to the latest one.

Definitely need a lot of patience for this one since you need to wait for at least 30 days but it's all worth it. I have to agree when you said that you put them in a container for it to avoid being damaged. Great tip! Thank you for sharing!

Great Article! Thank you for sharing this is very informative post, and looking forward to the latest one.

Great Article! Thank you for sharing this is very informative post, and looking forward to the latest one. If you are looking for hydroponic supplies here in Australia just visit thegrowshop dot com dot au.

Thank you so much for this clear description.
I’m eager to plant them once frost is clear.

I love to sit and watch them. They are absolutely beautiful.

I live in the very NE corner of Georgia and would love some Common Milkweed seeds from anyone who has extra from last fall. I did bring many seed pods back from Western PA and they were full of seeds. Gave many to neighbors and for mine, I simply lightly sowed them into the ground in January (as they would in nature). Many came up!!! They were just baby seedlings, about 1/2 high, then they were gone!!! Not sure if bugs, caterpillars or rabbits got to them. I protected them from rabbits by covering with a hard yard cloth (1/4" screen) , but one day, they were no longer. I will try to plant in pots indoors first and then transplant after last frost. So, if Dick Sent (one of the commenters) has any extras, I'd love to have some. Thanks.

I just started making my garden a place for hummingbirds and our monarchs. I live in the Santa Cruz Mountains and am aware of the need for milkweed for our butterflys. I purchased a mature milkweed and now working on the seeds and how to grow my own plants. It's August.Any suggestions are welcomed regarding the seeds. They are from Home Depot Asclepias Fascicularius. It looks as though I should put the seeds in the fridge for 30 days? The weather here has been in the low 80s If you have a suggestion for this Newby please feel free to comment. I thought that Monarchs were mainly here in California and I'm glad to here they live in many places and have many folks working to help them. Thanks to all who help them.

So totally new to this and had some seeds given to me. What do you do with them during the months leading up to putting them in the fridge?

So useful! Thanks for sharing these tips.

Great information here and wonderful comments. I life in So. Fla. and have a Butterfly Plant Exchange every other month. We've been doing it for 2 years and we always have about 25-30 show up to share seeds, seedlings, cuttings, etc. We post the events on a Nextdoor group and use sign. up dot com to manage RSVPs. (We also have wonderful refreshments). Different people volunteer to host it, affording an opportunity see active gardens and get ideas/learn more. I encourage others to start a Butterfly Plant Exchange in their area.

I harvested seed in the fall, and I plan to wait until spring to start the stratification process so I don't grow them too early to plant.
Are there any specific storage requirements until then?

If they require cold stratification it's best to keep them in the fridge in a zip lock bag, for any other storage you can use paper bags until ready to plant. Good Luck. :-)

Any advice on getting purple milkweed going? Last year I tried both inside and outside and only got one small plant out of 20 seeds. I’ve purchased more seed this year hoping for better results. I have lots of extra swamp milkweed if anyone needs any. Great article, thanks for your help.

I still have quite a bit of butterfly weed seed that stayed put on the plant over the winter in eastern Ontario. Would that satisfy the requirement for moist cold stratification if I just start planting the seeds elsewhere in the yard to expand my butterfly weed plantings? I've had good success with the plants (purchased from a native plant nursery) and they bloomed last year for months (with deadheading of the seed pods until early fall).

Hi Heather,
They should be ok to plant those seeds anywhere you like now.
I've put a page together for our local group in Windsor, ON that has almost all you need to know to become a milkweed expert. :-)
http://savethemonarchbutterfly.ca/milkweed-general-info.pdf

What would be the recommended cold stratification period for Antelopehorn Milkweed Asclepias asperula?