How to Collect & Grow Milkweed Seeds (Asclepias)

If you want to grow milkweed from seed, fall is the perfect time to collect seeds and start sowing. We know we can’t have monarch butterflies without specific milkweed plants (Asclepias spp.) so we need to protect this vital, host larval plant. Plus, the native species make a beautiful addition to the garden.

Also see How to Sow Seeds Indoors for Outdoor Plants for other types of seed propagation.

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Growing Milkweed

There are a few options for collecting milkweed seeds for propagating new plants. You can collect seed from existing plants, purchase seeds, or perhaps receive some as a gift.

No matter what, it is important to know what you’re growing. These tips are intended for hardiness zones 4 to 8.

While many milkweeds (Asclepias spp.) are native to parts of Canada and the United States, it’s not one-plant-suits-all. Some species play nice, others may be deemed aggressive or harmful in your area and should not be planted. Before adding any milkweed plants to your garden, check with your local conservation office or university extension office to ensure they are not on the naughty list.

Another consideration we have is butterflies. We can grow milkweed like Common milkweed (Asclepias syriaca) which is a food source for monarch (Danaus plexippus) caterpillars. But most important is the bigger picture, doing what we can to provide diverse habitat to support all of our native wildlife. Protecting monarchs alone will do nothing if we do not have suitable food and habitat for everything inter-connected with them.

Growing for wildlife also means avoiding pesticides and herbicides. There is no sense in attracting living things just to harm them.

And finally, milkweed—if non-tropical—is a seed that requires stratification. This is a process that occurs naturally in cold climates, where the seed is exposed to period of cool, damp conditions near freezing over winter which in turn readies it for germination in spring.

When growing your own from seed, you can naturalize the process and let winter handle it with outdoor sowing in fall or mimic these conditions in your home for indoor seed starting.

Either way, the first step is to know what you’re growing and from there, gather seeds and get sowing.

I’ve provided more tips and details on all of these points below.

Collecting Milkweed Seeds

If you already have seeds you can jump to the next step.

These tips will help you collect milkweed seeds to sow your own plants. This is particularly helpful if you intend to forage for seeds.

Get familiar with milkweed: there are some imposters out there. Prior to flowering, dogbane (Apocynum cannabinum) and smartweed (Polygonum genus) may fool you. In fall, once the infamous seed pods are popping open, revealing the fluff (coma) and seeds inside, it’s easy to identify.

Know your local laws. In some areas it is illegal to remove any natural materials from public or private property. I collect the seeds from the plants in my own garden. I also let my milkweed self-seed, meaning I just leave it and it does everything for me.

Grow diversely. Because milkweed plants tend to be clonal (closely related), it is worthwhile to collect seeds from several different areas for better germination rates and diversity. Trading with a friend is a good option.

Wear gloves. The sap of milkweed can be harmful to both skin and eyes.

Timing is everything. Milkweed seeds are not viable if collected too soon. You can be too early, but probably not too late. In the images (above), the first image shows immature green pods. These are not ready yet. The second image shows the pod wide open with the fluff and seeds. That’s your time to collect seeds before the wind and rain disperse them.

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The image (above) show a milkweed seed pod. The seeds are the little brown things sitting in the fluff. The part we see is actually the seed casing. The actual seeds are inside which are usually a creamy white color if they are still viable.

When we grow milkweed from seed, we plant the entire thing (casing and seed). Exposure to water and warmth gradually breaks down the casing, allow the seed to sprout. Some growers also scarify the seed coats (gently rough them up with a nail file or sandpaper) to further assist the process.

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Double check for viable seeds | Some of the seed casings will be empty (not have seeds inside) or the seeds may be old and not viable. You can always cut a few open to check.

Choose insect-free seeds. If the seed pod has milkweed bugs on it, the seeds are probably no longer viable (won’t germinate). Choose seeds from other bug-free milkweed plants instead.

Remove the fluff. Once you’ve collected your seeds, you want to allow everything to dry and remove any fluff and other plant materials. 

Store your seeds. Keep them in a cool, dark place. This has helpful tips on the best way to store seeds at home.

Growing Milkweed from Seed

Once you’ve confirmed that your milkweed seeds are suitable for your growing in your area, there are a few options for sowing. These tips are for non-tropical milkweeds that grow in four-season climates.

Fall is the time for direct sowing seeds outdoors. The benefit is that nature provides the winter conditions needed to stratifiy the seeds. As mentioned, stratification is a process where the cold and damp of winter naturally prepares the seeds for spring germination.

Another option is to sow the seeds indoors. It’s a long, slow process, just as it is outdoors, but can be done. There are milkweed enthusiasts who have their routine down to a science and get good germination rates. Ultimately, they are ensuring that the seeds have exposure to cold and damp over a sufficient period of time to ensure their seeds sprout and then provide optimum seed starting conditions. If this is something that interests you, it’s a fun pursuit.

You may also want to try winter sowing in containers.

No matter how you do it, it will take several months including the cold stratification period to eventually grow.

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Outdoor Seed Sowing

Fall

• The perfect time to sow milkweed outdoors is right when nature does it: when fall weather is consistently cool but not yet freezing.
• Sow the seeds and cover with one-quarter inch of soil. Keep watered until the ground freezes.
• Mark your sowing area with tags so you don’t mistake the germinating plants for weeds in spring.

Winter

• It’s not as successful as fall sowing, but you can also “winter sow” the seeds in containers. There are photos and instructions here. While the process is called “winter” sowing, start milkweed by November or December to allow enough time. And be sure you allow the cold to reach your seeds.

Spring

• Spring sowing can work if you have stratified the seeds first. See Indoor Seed Starting below for instructions.

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Indoor Seed Starting

If you are starting your milkweed seeds indoors, allow approximately 3 to 4 months from the time you stratify in the fridge until transplanting outdoors. You can transplant outdoors from spring to fall so long as the ground is not frozen and you have time to allow the roots to establish.

If you are new to this, I have a detailed ebook on indoor seed starting here.

This is how I start milkweed from seed indoors. There are lots of variations online.

Soak seeds in warm water for approximately 12 hours, then pat dry.

Place seeds in a plastic food bag with a combination of perlite and vermiculite or within moist paper towels or dish towels. The towels should feel damp but would not drip water if squeezed. You can also use potting mix for this. The drawback is, it’s easy to misplace the seeds because they are the same color as the mix but try it if you like (I do it this way).

Stratification. Stash bag in fridge for 45 days, sometimes it works in a shorter time but this seems to be the sweet spot for many of us who experiment with this at home. The point is, they need the moisture and cool temperatures over a certain period of time for this to work. Set a reminder on your phone to check every week to be sure everything is moist, but not too damp or dry.

After 45 days, sow seeds one-quarter inch deep in small pots on a tray using potting mix. Place directly under grow lights or by a sunny window. Water from below by adding water to the tray as needed. A soil temperature of 70-75°F (21-23°C) is ideal.

Germination typically takes 15 days or so if conditions are right. Continue watering as needed.

Harden off. When seedlings are at least 6-weeks old and 2 to 3-inches tall, prepare them for life outdoors by hardening off over a 1 to 2-week period, depending on how drastic the change will be.

Transplant into the garden. Choose a full sun location and keep watered until well-established and ready to survive on their own.

Related: Clever Tip for Saving Your Best Garden Seeds

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Seed Sowing Summary

• Before growing milkweed, find out the best varieties for your area, ensuring they are non-invasive.
• Collect milkweed seeds in late fall when the seed pods are brown and open or easy to pop open.
• Allow seeds to dry completely before storing them and remove any fluff or plant material first.
• The seeds require several weeks of cold temperatures to germinate (stratification).
• Direct sow in fall or indoors in spring.

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Milkweed Facts

Milkweed (Asclepias spp.) is an American herbaceous perennial with over 140 known species. This plant has gained attention in recent years because some types are the sole host plant for monarch butterfly larvae (babies). No milkweed means no monarchs. And any species loss affects the entire food web.

If you are growing specifically for monarch butterflies, find native species for your region that we know monarchs and other milkweed butterflies (and insects) prefer, either as host larval plants for their caterpillars or as a nectar source.

Milkweeds are also a food source for bees and many other beneficial insects and their prey. The fluff (called coma) from the seed pods provides nesting material for birds and animals.

The ‘milk’ of milkweed is a sappy, latex-like substance. It is irritating to touch and toxic to animals. Historically, hunters used milkweed in arrows to weaken prey animals.

Milkweed flowers have complex structures and the pollination process is interesting. The pollen is contained in sacs (pollinia) that stick to the feet of visiting pollinators including bees and butterflies. Upon flying away, the sacs break open, releasing the pollen into the flower, or it may be carried away to another milkweed for cross-pollination. Sometimes, they are too sticky and the insect is trapped.

Monarchs have co-evolved with particular milkweed species in different regions, using it as a natural defense. Ingestion of the sap (which contains cardiac glycosides) by the monarch caterpillars makes them taste horrible to potential predators like birds. 

Those orange and black markings are code for: don’t eat me or you will regret it! 

Other butterfly species have also adopted these colors to foil the birds. They don’t eat the milkweed leaves but they look like they do, so those predators leave them alone too. It’s very cool!

The familiar, fluffy white stuff found in milkweed pods called coma, also known as silk, floss, plume, or pappus is used for insulating clothing. It’s less successful as a pillow stuffing lacking fluffiness for comfort. Coma is also good at absorbing oil with potential for absorbing oil spilled in waterways.

Frequently-Asked Questions

Can I just scatter milkweed seeds?

You can. That’s how nature does it. But, if you want the plants in a certain place or better odds of germination, they will need your help.

If you have not stratified the seeds first, sow them directly outdoors in fall using these instructions so nature can do it for you.

If you are sowing at any other time of year, give them their best chance by soaking and stratifying them first.

And, if you do “scatter” them, cover them with some moist soil to keep them in place.

What is the best time to plant milkweed seeds?

Outdoors: fall.

Indoors: any time so long as you can get the young plants established before winter. I find it takes around 3 to 4 months from seed to transplanting time.

How long does it take milkweed to grow from seed?

This can really vary depending on growing conditions.

This example applies to indoor seed starting:

Stratification: 6 weeks
Germination: 2 weeks
Ready to transplant: 6 to 8 weeks

Total: 14 to 16 weeks (3 to 4 months)

Should I soak milkweed before planting?

When the seeds self-sow outdoors, nature “soaks” them over the winter into spring thaw.

But you could help them along by presoaking the seeds before sowing.

When starting these seeds indoors, I soak them before beginning the stratification process in the fridge.

Does milkweed come back every year?

Yes. If you’re growing milkweed where it belongs and it’s getting what it needs, it will come back each year.

And, if you leave the plant to produce seeds each fall, some of those seeds will very likely self-sow.

Some gardeners complain that their milkweed is too good at self-sowing. If this is a concern, remove the seed pods before they mature in fall.

Can I sow milkweed seeds in winter?

Yes, but. If you can sow them (one-quarter-inch deep) and there are a few months of cold weather (around freezing or colder) still to come, it can work. See the sowing instructions for more information.

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I hope you’ll try collecting and growing your own milkweed seeds. There are many different approaches to growing it and my tips are just what works here. So be willing to experiment and find what works best where you are.

Now go grow some butterflies!

~Melissa the Empress of Dirt ♛

Sources | Read More

• How to collect and grow milkweeds to help monarchs and other pollinators| Michigan State University Extension
• Save Milkweed seed and help the Monarch Butterfly | University of Illinois Extension
• Collecting Milkweed Seeds | Michigan State University Extension
• Growing Milkweeds | Monarchwatch.org
• Milkweed Regions & Seed Needs |Monarchwatch.org
• Xerces Society | Monarch Conservation | Find Milkweed Seeds
• Asclepias (Milkweed) | Wikipedia – see images of various types