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. How to Harvest & Plant Milkweed Seeds: Learn how to collect, harvest, and plant common milkweed seeds to attract monarch butterflies to your garden. Saving butterflyweed seeds Monarch butterflies aren’t the only ones that love butterflyweed. Finding Asclepias tuberosa or Butterflyweed seed pods is relatively easy. Getting the seeds without
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.
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. Certain milkweeds are a host larval plant for monarch butterflies and their caterpillars cannot survive without it.
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.
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) 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. 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.
No matter how you do it, it will take several months including the cold stratification period to eventually grow.
Get Milkweed Seeds
Outdoor Seed Sowing
- 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.
- 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 sowing can work if you have stratified the seeds first. 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.
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 flower pots 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.
Sow Indoors | 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. 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.
How to Harvest & Plant Milkweed Seeds
Learn how to collect, harvest, and plant common milkweed seeds to attract monarch butterflies to your garden.
Support monarch butterflies with milkweed
Want to help stop the decline of monarch butterfly populations and bring more of these fluttering beauties back into your garden? Plant milkweed — it’s the sole food source for monarch caterpillars and is attractive to many pollinators for its nectar-rich flowers.
Where to buy native milkweed seeds & plants
The Xerces Society can help you find a seed source in your area. Visit their Milkweed Seed Finder here for more information.
, 800-925-9387 , 866-417-8156 , 800-476-9453
You can plant milkweed starter plants or plugs purchased at specialty nurseries like the sources listed above. Any species in the milkweed family will do, but the easiest to grow is the common milkweed, Asclepias syriaca. Plant them in full sun in groups of three to six spaced 6 to 24 inches apart scattered around your garden. Smaller groupings are less prone than mass plantings to insect or parasite infestations or predators. Also keep in mind that milkweed plants have some toxicity — so keep them out of places where livestock may graze and don’t let pets or children chew on them.
It’s also easy to collect milkweed seed (be sure to ask property owners first) and start it yourself. Scroll down to the gallery for our tips on how to collect the seeds from the pod.
Planting milkweed seeds
Milkweed seeds need to be stratified to help them germinate. Stratification is when a seed is moistened, chilled or frozen and thawed, breaking down germination inhibitors on the seed coat, such as waxes, hormones, oils or heavy coats. Milkweed seed planted in fall is naturally stratified. Spring-planted seeds need to be pre-chilled in the refrigerator, which replicates the natural process of snow and cold breaking down the seed casing.
Planting milkweed seeds in fall
Plant seed in fall in a sunny location. Simply sprinkle seeds on well-tilled soil and pat them down, add a topdressing of soil, and water them in. Fall-sown seed will be naturally stratified outside.
Planting milkweed seeds in spring
You can plant milkweed seeds in early spring as soon as the soil can be worked, but they will need to be stratified for 2 to 3 months in the refrigerator before planting in spring for better germination.
When emerging milkweeds have three to four sets of leaves, thin seedlings to 6 inches apart.
Starting seeds indoors in winter
You can also start stratified seeds indoors in late winter. Sow 2 to 3 seeds in a pot filled with seed-starting mix, cover with ¼ inch of mix, water lightly and set under lights. Germination takes 7 to 10 days. Plant seedlings outside in a sunny spot when they have 3 to 4 sets of leaves and the ground is warm.
Saving butterflyweed seeds
Monarch butterflies aren’t the only ones that love butterflyweed.
Finding Asclepias tuberosa or Butterflyweed seed pods is relatively easy. Getting the seeds without a load of the white “silks,” however, can be a bit more difficult unless you know how to open and hold the pod for seed saving.
As you’ll see in the short video, you want to start by tearing off the fatter end – the part that was attached to the stem.
Then carefully pry the pod open and firmly grasp the pointy end. (That’s what I was signalling by clamping my fingers in the video – hold the pointy end firmly!) This keeps the silks firmly in place so you’re removing the seeds only. Then scrape.
After collecting the seeds I like to leave them in an open container for a few days so they can dry out before placing them in the refrigerator.
You can also see here for full instructions on how to sow immediately or to save and cold stratify the seeds.
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