Winter Sowing Milkweed Seeds Part 1: Supply Checklist
Each year I try to implement new gardening techniques that get more results with less work. This year I’m adding winter sowing to that list. Is winter sowing right for you?
3 Big Advantages to Winter Sowing Milkweed
Almost everyone in North American can benefit from winter sowing milkweed seeds. The few exceptions are those that live in regions without a true winter.
1. Winter weather provides a natural cold stratification process. When seeds are subjected to cold before gradual warmth, this breaks their dormancy and causes them to sprout. Warm weather varieties (e.g. tropical milkweed) don’t require this.
2. Seedlings sprout early inside their miniature greenhouses giving you a head start on garden season and north-migrating monarch butterflies.
3. You have more control of where plants grow. If you direct sow in fall or spring, seeds can get moved around by weather or wildlife before they germinate.
When to Wintersow
Some start sowing as early as the winter solstice (which is just before Christmas). Earlier start dates are recommended for those further south, since freezing temps are in shorter supply.
I’ve started milkweed seeds inside before with less than one month of ‘refrigerator’ cold stratification. Starting seeds by February should be more than enough time (in most regions) to create the desired outcome.
Native milkweed is the cornerstone of a successful butterfly garden, so start with those species if you are just getting started. Once you have natives established, consider other non-invasive varieties to attract even more butterflies.
What’s native to your region? Check out my milkweed resources pages, which lists the native region for 25+ milkweed varieties.
Common Milkweed Varieties that are Wintersown
These are the native and perennial milkweed species we planted to build our foundation…
1. Asclepias incarnata (swamp milkweed)
2. Asclepias purpurascens (purple milkweed)
3. Asclepias syriaca (common milkweed)
4. Asclepias tuberosa (butterfly weed)
5. Asclepias verticillata (whorled milkweed)
6. Asclepias sullivantii (prairie milkweed)
Less Reliable Milkweed for a Northern Butterfly Garden
Once those varieties were established, our sowing options became more adventurous…
1. Asclepias variegata (redring milkweed) native to most of the eastern US and Canada. Suited for hardiness zones 3a-9b. (this has been reported to have a better germination rate using water stratification)
2. Asclepias viridis (spider milkweed) native to much of the eastern US. An early milkweed for USDA zones 5-9. Surprisingly, we had excellent germination rates winter sowing viridis during the 10th coldest Minnesota winter on record…which was followed by a cold spring with torrential rains! Three years later, it keeps coming back…
Winter sowing milkweed doesn’t require a huge investment (of your time or money!) and the rewards can be quite substantial when spring rolls around. You’ll be happy to learn most of the tools needed are already inside your home.
Winter Sowing Containers
These are some container options that have been successfully used by other gardeners. Consider trying a couple methods to see if one works better for you. Keep in mind all containers must also be clear enough to allow light to penetrate the soil.
Any container should have the ability to hold up to 4″ of soil, with ample room up top for seedling growth.
Here are some containers to consider for your winter sowing milkweed adventures:
1. Disposable food storage containers with snap-on lids
2. Plastic Milk Jugs
3. 1L or 2L plastic soda bottles (we have had the most success using these containers)
4. Clear plastic storage bins with snap on lids (The lids don’t have to be clear)
5. Clear plastic Cups
6. Ice cream buckets
7. Grocery store Rotisserie Chicken container
8. Containers for baked goods like cakes, muffins, and cookies
9. Distilled water jugs
10. Plastic fruit containers (eg strawberries or blueberries)
Use a good all-purpose potting soil, seed starting mix or make your own. Do not use a moisture-control variety, because excess moisture could lower germination rates for some milkweed species.
We use pro-mix which has sphagnum peat moss and perlite mixed in to allow more air around developing plant roots and improve drainage. We are also experimenting with the seed starting mixes.
Other Tools Needed?
Duct tape, a scissors or box cutter, a marker for outdoor use, sturdy plant labels, and a drill (or something that will make drainage holes in your plastic containers).
Weather Resistant Garden Markers
Once you’ve got the necessary tools, it’s time to sow your seeds of monarch love! Click the link below for step-by-step winter sowing instructions:
11 Simple Steps for Winter Sowing Milkweed
Please see comment section below for more info about winter sowing tools…
I just received some local milkweed seeds (well actually I got a Pod) and I was going to Cold Straiate then in the fridge for 30 days, then germinate them in Peat pots – guessing this would then put them best for fall planting but they will have germinated and started growing by the time winter rolls around – will this hurt the new little plants?
Hi Christine, if you’re in a region with a true winter, I would skip the CMS and just fall plant the seeds.
Hello. I am in central Ohio, about 20 miles south of Columbus. We collected milkweed seeds this past fall. I believe it is too late to put them outside in plastic jugs for winter stratification. Do you recommend putting them in the refrigerator now until we plant them in April? We are doing an Earth Day event with the Girls Scouts and I’m just trying to make sure we have the most successful pollinator garden possible.
Hi Scott, it’s getting a little late in the season to rely on cold temps for a solid month…a more reliable option is:
Cold Moist Stratification
I am in the Northeast Region, and the milkweed that is native to the area is Asclepias incarnata (swamp milkweed). I’ve tried looking everywhere, but can’t seem to find this variety in stores. I have Home Depot, Walmart, and some other stores. I am trying to keep it to the native variety. Any suggestions on where I can find this?
Hi Barbara, if you want seeds, these will be easy to find online in the suggested milkweed stores section…plants should be easier to find closer to spring.
Suggested Milkweed Stores for Seeds and Plants
Are there any milkweed types that aphids don’t really like ?
unfortunately, I’ve pretty much seen them on all milkweed varieties…probably least on A. tuberosa, but that’s not a monarch favorite either.
Hi Tony. Glad I found your site. This is the first year I’m planting milkweed (swamp) and other flowers specifically to attract the Monarchs. I grow all my flower and vegetable plants and keep the seeds in airtight freezer bags with silica gel and packed in a plastic container. Reading your article here, I’m late getting started with the Milkweed, and possibly with the Marsh Mallow too. Since I have the seeds in the freezer, does that count toward stratification and, if not, can I at least cut down the time in the refrigerator? I’m in south central Missouri and plan to grow the plants inside. Also, should I avoid putting the planted seeds on the heat mat with other seed starts? They’ll be under lights in a cool basement. I also have a plastic tunnel on my raised garden bed and can put plants out in peat pots in early spring if that’s better. Have never been so paranoid a planting a seed before! But I want those Monarchs back. Appreciate your your work to save the Monarchs.
Hi Ruth, yes…storing seeds in the freezer counts as cold stratification. The ‘moist’ part can help the seeds to germinate faster. More info here:
Cold Moist Stratification
Also, I only use a heat mat until the seeds have germinated. Yes, you could try some seeds in your raised bed set up to. It’s always good to try a couple different propagation methods to seed what works best in your region…good luck!
I followed your instruction for sowing milkweed seeds in containers last winter and had great success. I started a 10’x40′ milkweed garden in the spring and had many cats by mid-late summer. I even bought one of your tents and watched some of them pupate up close. BTW, the Monarchs seemed to prefer the red milkweed for their eggs over the common milkweed.
I have a question for you. Is the “greenhouse” effect of the containers important? I have a salad table outside that I used for sowing seeds this time which I covered with hardware cloth to keep the birds off. Will this work? (I also started several containers for insurance.) The table won’t provide a greenhouse for the seeds, but it will allow the winter weather to have its effect. What do you think?
Best regards, Kellie
Hi Kellie, congrats on your sowing success! The greenhouse effect increases the speed of germination…obviously you don’t ‘need’ it if you think about all the seedlings that come up in your garden each spring. Gardening is all about experimentation and different propagation techniques work better/worse depending on your region. I’m sure covering with hardware cloth will work, but the seeds might not germinate as quickly…good luck!
I collected my milkweed seeds last fall, made sure they were dry and placed in zip baggie. But I thought I was to store in freezer until this spring. I am confused as to whether I was to store in freezer or refrigerator. Help… I hope I didn’t ruin the seeds.
Hi Laurie, some people store their seeds in the freezer or refrigerator….I store mine in a cupboard. As long as they’re not warm weather varieties, your seeds should be fine.
Hello everyone, I have a question… and a bit of a problem, I have recently found some milkweed seed pods with most of the seeds missing, and I’m not sure what type of milkweed it is so I’m not sure when or how I should plant the seeds. Happy early almost spring! And thank you to anyone that helps!
Hi Madison, it’s a lot easier to start seeds when you know what you’re planting. Otherwise, it’s just a guessing game. You could still try winter sowing (if you’re in a region with a true winter) and reserve a separate spot in your garden to plant the seedlings. Once you figure out what they are, you can transplant them if needed. good luck!
Winter sowing as described in the article works, I’ve done it successfully. However, it’s far better and easier to grow more much easier under grow lights but you must cold stratify.
Hello and happy January. I will be sowing on Sunday! I just got into this and have LOTS of extra seed in case someone wants some. They are common milkweed from Michigan. I have 5 people already at work that planted seeds in December, and my sister took some to plant near her home.
My question is this: How many plants do you need for each cat? I have about 100 seeds planted in three containers so far and will sow more tomorrow.
Thanks for the great work and info you are doing. Love it!!
Hi, I would like to purchase some seeds from you. I live near Cincinnati Ohio and wonder if they will make it here. Our climates are similar. I am a senior citizen and love to grow things so would love to try this. Will be waiting for a reply. You cam msg me or e mail. Thank you, Phyllis
Hi Cindy, over two weeks it takes just 1-2 caterpillars to finish off an entire milkweed plant. It sounds like you should have plenty of milkweed available when they monarchs make it back to Michigan this summer.
Tony, I’m growing tropical milkweed cuttings indoors for the first time this year and I can’t get rid of the aphids!I followed your instructions in the blog and am using the hydrogen peroxide spray you recommend, but they keep coming back. I’ve taken to squishing them, but it’s really starting to take a toll on the plants. How can I get rid of them? Can I use real pesticide since we’re many months away from the cats feasting on them?
Thanks for your help!
Hi Sue, hydrogen peroxide kills fungus gnat eggs in the soil, but not aphids.
To treat aphids indoors, I use cotton swabs dipped in isopropyl alcohol to kill them. here’s more info about aphids:
Stop Aphids from Taking Over Milkweed
Tony thanks so much. They’ve been driving me crazy. Oh I’m gonna get them now!
So I am in Southern Ca. and have difficulty propagating narrow leaf milkweed seed. Any suggestions?
Hi Gao, check out my western resources page to see if you can find someone with first hand growing experience for this particular milkweed species:
Western Monarch Resources
Regarding winter sowing in containers, which is the the best type of soil to use: starter mix, potting mix, or potting soil? Isn’t potting soil heavier than the others?
Hi Pam, that sounds like a great idea. See starter mix has much finer particles than regular potting soil, so it might yield a higher germination rate. Maybe try some containers with potting soil and some with seed starting and see if you noticed a difference…
I love in Ellsworth, Maine. We have milk weed all over the place. A neighbor has a whole field of it!
You mentioned once that it doesn’t transplant well. I’m thinking you meant transplanting from the ground from and established field.
I don’t even know what kind of milk wee we have! Is there any way you can help me out?
It is pink and smells sweet.
The seeds need to be in the frig for a month starting at the end of December?
Hi Rebecca, if you’re winter sowing in your region you can probably wait until February since you’re in a northern region…your seeds will get a natural cold stratification from your winter weather. Refrigerator stratification is for warm weather regions or if you miss planting in fall/winter. It sounds like your neighbor might have common milkweed. Here’s more info:
Common Milkweed for Monarchs
Just read through steps one and two – live in Northern MN.
Will try the “winter method” with my seeds, in February.
Do I leave the seeds in the baggies for now? Sealed or open?
Hi Kim, as long as the seeds are completely dry you can seal the bag. Mold issues only occur when seeds are wet. I let seeds sit in a bowl 24 hours before storing them.
Hi Matt, thanks for the great info. I’d just like a little clarification. I harvested some milkweed pods from a field near me. the pods opened easily and the seeds are brown. I live in Ohio so I will get a good winter and would like to winter sow them, probably right after Christmas. what do I do with the seed pods until then, that’s a good 3 months. do I seperate the seeds and put in plastic bags? I worry about mold. or just leave it all together pods and all and let dry naturally? thanks, I appreciate your help!
Hi Caty, I would separate the seeds now. As long as you let them dry, you can store them in a plastic bag without worrying about mold. Here’s more info:
Harvesting Milkweed Seeds
I enjoy this so much. A good friend I used to work with (she retired) used to bring in this 3 sided glassed box where she used to have the monarchs pod on the top. She would bring it in to the residents of our nursing home and they would enjoy watching the process. She would let them bring them out to fly free when they were ready. Its such an easy thing to do and so helpful. Really Really cool!! I love it. I will be doing this process too. Thanks for doing this.
I’ve got my milkweed seeds stratifying in slightly moist sand to plant soon. Wherever did you get the redring milkweed seeds as the plant is supposedly ever so rare? Ready for super sow Sunday but it might be on Monday that they get planted.
Hi Brian, I had gotten them from a gardener a while back and the seeds weren’t viable. Every once in a while, I’ll search for seeds online but no luck. One of these years, hopefully…good luck with your winter sowing containers!
Hi Tony, I have had a surprising experience. Here in southern Louisiana we have not had a cold winter. The few times we have had a freeze I have covered up my milkweed trying to save it for the coming year. It is growing fine and blooming too. Well yesterday I go out to check the plants in the garage and to start planting my seeds for the winter in my trays when I all of a sudden I see a cat!
I also had to cover the plants outside for a freeze last night. Well I searched all the milkweed in the yard…I have 9 cats!
My questions are 1) I have enough milkweed to get them through but what about the butterflies? I don’t have any flowers. 2.) Are these still the super butterflies that live 6 months? Can they still make it to Mexico? They are roughly about two weeks old now.
I have gathered them together and have them inside now to keep them warm.
I would appreciate if you could give me some advice on this surprising event. Thank you Jackie
Hi Jackie, what an unexpected January surprise!
I don’t think butterflies will migrate this late in the season, but who knows? They could possibly survive winter in your region if you temps remain on the mild side…if they stay, they will probably live out a shorter life span like summer monarchs. It is possible they could mate with returning migrators.
If they eclose during a cold spell, you may have to keep them a few days. In that case you would need to feed them. There is some info on this post about feeding/releasing adult butterflies. Good luck with your first batch of the new year!
Release Monarch Butterflies
Question: I’ve brought several milkweed pods from NH to Long Island NY. Can you provide info to help them survive in this different climate zone please? Thanks!
Hi Bridget, I wouldn’t worry too much about transporting seeds from one location to another. I would focus on whether the species is perennial to your region, which I’m guessing it is since NY and NH are both out east. You can winter sow the seeds or try fall planting. Here’s more info:
Fall Planting Milkweed Seeds
how do you get milkweed over the winter?
Hi Josie, are you looking for milkweed seeds and plants? If so, check out my resource page:
Milkweed Plants and Seeds for North American Butterfly Gardens
I started a butterfly garden a few years ago and this past summer collected all my milkweed pods to donate and give to friends to help promote native host plants for Monarchs.
My concer however is that I gathered all the pods at the summers end and they’ve been on a shelf in the house since. They seem very try and brittle now. Does mean they will be no good now for winter sowing and harvesting?
Any feedback would be appreciated!
Hi Zack, is it possible you picked the pods before the seeds were ripe? We typically separate all our seeds when we harvest them and store them in paper or plastic bags once they are fully dry.
It can’t hurt to try winter sowing, but make sure you have an alternative source for seeds or plants if things don’t work out…good luck!
This is the first year that I have collected warm weather milkweed seeds (tropical and goose/balloon). I have read that the refrigerator is generally the best place to store seeds as long as you keep your seed storage containers away from the freezer section of your refrigerator.
I was wondering, how do you store your warm weather milkweed seeds over winter?
Hi Brian, I just keep mine stored in a cupboard, and then soak them in warm water 24 hours before planting.
Interesting info here!
Quick question about planting of milkweed seed. I have read some information from other sources that say that milkweed seeds need light for germination and therefore should not be covered with soil when planted. Can you comment on this?
Here in Iowa, I will be working to establish Sullivant’s milkweed, Butterflyweed, and swamp milkweed.
the 3 milkweed species you are growing require cold stratification. You can do this naturally with winter sowing or place seeds in the refrigerator in late winter and spring. I plant seeds about 1/4″ deep and cover with soil. You should have good germination rates this way, provided you have viable seeds.
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