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.
If you want the big picture, this explains everything you can do to help monarchs in your garden.
Growing Milkweed
With over 80 species of milkweed plants, it is important to know which ones are suited to your specific growing region.
Once you know which species are suitable, you can save seeds to grow new plants.
Wildlife Milkweed Supports
Various milkweeds are host larval plants for both butterfly and moth caterpillars:
- Butterflies: Monarch (Danaus plexippus), Queen (Danaus gilippus), and Gray Hairstreak (Strymon melinus).
- Moths: Unexpected Cyncnia (Cycnia inopinatus), Delicate Cycnia (Cycnia tenera), Isabella Tiger Moth (Pyrrharctia Isabella), Milkweed Tussock Moth (Euchaetes egle), Stalk Borer Moth (Papaipema nebris), Striped Garden Caterpillar (Trichordestra legitma)
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 generalized 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 is the eco-system as a whole. Protecting monarchs (Danaus plexippus) alone will do nothing if we do not have suitable food and habitat for the entire inter-connected food web—all the plants, animals, insects, and more that rely on one another to exist.
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. This has a complete tutorial on stratifying seeds.
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.
What Do Milkweed Seeds Look Like?
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) or clip off the tips with nail clippers (careful not to touch the actual seed) to further assist the process.
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.
If you are collecting a large volume of seeds, there are lots of tips online for ways to remove the seeds readily without too much fluff fuss. There are also videos like this one showing how to use a shop vacuum to separate the seeds. The fluff is trapped by the filter; the seeds fall to the bottom of the canister.
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 stratify the seeds. This is how I sow native seeds including milkweed outdoors during the cold seasons.
As mentioned, stratification is a process where the cold and damp of winter naturally prepares the seeds for spring germination. See How To Stratify Seeds for more information.
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.
Get Milkweed Seeds
Before acquiring seeds, check that the species is non-invasive and recommended by conservation groups in your region.
Milkweed Seeds | Botanical Interests
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.
- If possible, sow in pots as shown here, not the ground. This allows for better control over conditions. Either way, also cover growing area with hardware cloth to keep animals out.
- The right sowing depth is approximately one-quarter inch.
- Use markers or tags so you don’t mistake the seedlings for weeds in spring.
- Allow full exposure to snow and rain and check on a regular basis in case water is needed.
Winter
- It’s not as successful as fall sowing, but you can also “winter sow” the seeds in covered containers as well. This explains the winter sowing milk jug method. It is a fun method to try for a large variety of seeds.
Spring
- Spring sowing can work if you have stratified the seeds first providing cold, moist stratification in your fridge. See Indoor Seed Starting below for instructions.
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. Just avoid transplanting during heat waves.
If you are new to indoor seed starting in general to this, I have a detailed ebook on indoor seed starting here.
This explains cold-moist seed stratification in detail and gives other methods.
This is how I stratify and sow milkweed from seed indoors. There are lots of variations online.
You will place the seeds in moist paper towel or growing medium in the fridge.
Presoak Seeds (Optional) | Some advice says to soak seeds in water for 12 hours prior to placing in fridge to help further soften the seed coats. I’ve not noticed any particular difference whether I do this or not but it does not seem to do any harm.
Place Seeds In Moist Paper Towels Or Growing Medium | Place seeds between sheets of moist (not dripping wet) paper towel or in moist growing medium, perlite, or vermiculite and put everything in a plastic food bag or food container. Some gardeners use little flowerpots but that takes up more fridge space. I prefer paper towel in a ziplock bag because it’s easier to keep track of the seeds and uses little space.
Label and date your bags or containers with seed name, start date, and fridge end date.
Some avoid closing the food bag or container for “better” air circulation, hoping to avoid mold. I close mine and have not had any issues.
Stratification | Keep seeds moist and cold in fridge for approximately 45 days—unless you have specific information on your seed type that advises otherwise. In general, this takes 1 to 3 months for milkweeds. Set a reminder on your phone to check every week to be sure everything is moist, but not too damp or dry. The paper towel (or growing medium) must not dry out.
There is also a fast method where you switch between fridge and freezer every 24 hours for a week total. The catch is you can’t let the seeds actually freeze solid in the freezer. I put a tea towel around the bag to prevent this from happening. Done right, your seeds are ready in 7 days. But the only way to know for sure is to try sowing them.
Sow Indoors | After stratification, 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. Keep soil moist but not soggy. 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 (at least six hours total direct sun per day) and keep watered until well-established and ready to survive on their own.
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 and moisture to germinate (stratification).
- Direct sow in fall or start indoors in spring with cold, moist stratification.
Milkweed Facts
Milkweed | Asciepias spp.
Milkweed Growing and Propagation Guide
Herbaceous perennial
- Vital Habitat: Asciepias syriaca leaves are the only food source for monarch butterfly larvae. There are also other milkweed butterflies reliant on these plants.
- Wildlife Value: Provides nectar for hummingbirds, bees, and butterflies.
- Flower Colors: Pink, yellow, white, green, purple
- Precautions: Milkweed sap can be irritating to skin and harmful to eyes. Wear gloves when handling milkweed and wash your hands thoroughly when done.
- Some milkweed plants can be invasive or aggressive in some regions: research before planting.
- In Canada and the United States avoid Asclepias curassavica and other tropical milkweeds which causes environmental and (possibly) butterfly problems.
Shop Online: Milkweed plants | Naturehills.com
Milkweed seeds | Botanical Interests (both US Shipping)
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.
Milkweed Examples
Common milkweed | Asclepias syriaca (zones 3-9)
Pink or mauve flowers
Swamp milkweed | Asclepias incarnata (zones 3-6)
Pink flowers
Prairie or smooth milkweed | Asclepias sullivantii (zones 3-7)
Bright pink flowers
Showy milkweed | Asclepias sullivantii (zones 3-9)
Pink and purple flowers
Butterfly weed | Asclepias tuberosa (zones 3-9)
Orange flowers. Some cultivars have yellow flowers.
Monarchs will use this but it’s not their preferred host larval plant.
Tropical Milkweeds (Not Recommended)
The long bloom time of these tropical milkweeds may be detrimental to our monarch populations in part due to parasites.
Bloodflower or tropical milkweed | Asclepias syriaca (zones 9-11)
Red-orange with yellow flowers. Native to South America.
Asclepias curassavica is also tropical and not suited to cold climates,
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 tussock moth caterpillars (Euchaetes egle) are on the leaves
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
Milkweed germinates readily in nature when conditions are right but it can take some practice to sow it intentionally. The key is to provide an adequate period of cold, moist stratification, either naturally outdoors or using a fridge indoors to help promote germination.
While you can scatter seeds just as nature does, germination rates will be fairly low. The workaround is to sow the seeds outdoors in containers fully exposed to the elements from fall to spring. Cover the containers in hardware cloth or wire mesh to keep animals out. This has complete instructions on winter sowing native seeds. You can also stratify and sow seeds indoors for a head start.
The best time to plant milkweed seeds directly outdoors is fall. Milkweed needs at least six weeks of moist, cold stratification in winter conditions to eventually germinate in spring.
How long it takes milkweed to grow from seed depends on the growing conditions. For example, indoors, cold stratification in the fridge takes around six weeks, then, after sowing indoors, germination takes two weeks. From there, the plants can be ready to transplant after another six to eight weeks. In total, the process is approximately 14 to 16 weeks (3 to 4 months).
You can presoak milkweed seeds before sowing or ensure the soil is consistently moist. When the seeds self-sow outdoors, nature “soaks” them over the winter into spring thaw.
Perennial milkweed species grow back each year. If you’re growing milkweed where it belongs and it’s getting what it needs, it will come back each year.
You will also get new plants each year if the flowers are left to turn to seed as well.
Some gardeners complain that their milkweed is too good at self-sowing, growing aggressively. If this is a concern, remove the seed pods before they mature in fall.
Yes, you can sow milkweed seeds outdoors in winter so long as there are a few cold months yet to come. For best germination rates, sow in containers in a shady location. Cover containers with wire mesh to keep animals out but allow snow and rain in. Seeds will sprout when temperatures warm and light increases in spring.
Resources
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
- Getting Started With Seed Saving (Flowers, Fruit, & Vegetables)
Listen
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 moths and butterflies!
~Melissa the Empress of Dirt ♛
How to Sow Milkweed (Asclepias) Seeds
Equipment
Supplies & Materials
- 10 seeds Milkweed seeds
- 10 pots Small plastic flowerpots optional for winter sowing
- 1 roll Paper towels optional for fridge stratification
- 1 box Food storage bags optional for fridge stratification
- 1 bag Potting mix optional for sowing in pots
Instructions
Fall & Winter Outdoor Seed Sowing
- Sow seeds in ground (soil) or containers (with potting mix) approximately 1/4-inch deep.
- Place hardware cloth over planting area or containers to keep animals out.
- Water thoroughly.
- Mark locations (or containers) with winter-proof plant tags.
- Keep soil moist until winter freezes set in. Seeds will sprout in spring.
Spring Sowing Starting Indoors
- Slow Stratification: Pre-chill (stratify) seeds in moistened paper towel in plastic food bag and keep in fridge for 45 days. Check every few days and re-moisten paper towel as needed.
- Fast Stratification: Alternate between fridge and freezer every 24 hours for one week. Cover plastic bag with a dish towel (or similar) as needed to ensure contents do not freeze.
- After stratification period, sow in pots of potting mix and continue growing indoors.
- The best time to transplant outdoors is when plant is established with several true leaves and weather is cool, either in spring or fall.
Notes
- Make sure the milkweed you choose is recommended in your growing region and not invasive.
- Prior exposure to moist, cold (stratification) over weeks or months is necessary for milkweed seeds to germinate. This occurs naturally when sowing seeds directly outdoors in fall or early winter.
- Roughing up the seed coat prior to sowing may also improve germination.
- Check your seed packets for more tips.
