Save on Seeds, Perennials & Bulbs

How to Germinate and Grow Milkweed Seed

Instructions for preparing and planting Common Milkweed Seed (Asclepias Syriaca) and Swamp Milkweed (Asclepias Incarnata). We found these techniques best for growing results.

Common Milkweed Butterfly Weed and Swamp Milkweed
Common Milkweed up top, Bright orange Butterfly Weed on the left and gorgeous Swamp Milkweed on the right. All are host plants for Monarch Butterflies.

Let’s Get Started: Understanding Milkweed Seed & Germinating

Step 1: To start Milkweed seed we recommend starting inside, but before this happens Milkweed seeds need to go through a cold stratification period.  Cold stratification is very important for the germination and growth of Milkweed.  It helps break the seeds natural dormancy cycle.  To do this, we recommend placing Milkweed seed in a damp paper towel or damp sand in a zip lock bag and place in your fridge for 3 – 6 weeks (30 days). Place in an area of the fridge, where it won’t get damaged. We taped ours to the bottom of a refrigerator shelf.

Common Milkweed

Growing Indoors

Step 2: Planting - Once the 30 days are complete, it’s time to plant the cold stratified Milkweed seeds. We recommend planting in 2-4” peat pots. Fill peat pots ¾ of the way with seed starting potting soil and gently add water.  Water should be able to drain through the peat pots.  Once the soil is damp, place 1-2 cold stratified seeds into each pot.  To finish, place 1/4 inch of soil on top of the seed.

Watering - Gently water the planted seed to give additional hydration. The best way to water is from the bottom up.  Use a flat pan under the peat pots and add a half inch of water to the bottom of the tray. Don’t over water as it can cause fungus. Water every day or every other day as needed, the best way to test the soil dampness is to touch it. If the soil seems dry then add water; if it’s wet, wait for the soil to dry out to water.

IMG_5621

Light Requirements - For the next few weeks, make sure the Milkweed is either in a sunny window, in a green house or under a grow light. Milkweed needs lots of sun and warmth to grow.  If you’re using a grow light, make sure to lower the bulb closer to the pots or your seedlings may become leggy, as they stretch to the light. In our experiment, this happened to us. Ideally a sturdier stem is better. Cold stratified seeds should germinate and sprout within 10-15 days once planted.  In total Milkweed from the day they are cold stratified to growth can take 40 plus days, so be patient!

Tray of Seedlings

Other planting options: Place dry seed (not stratified) in seed starting soil and plant in peat pots under a grow light or in a greenhouse to germinate seeds.  The success rate for this is low and more difficult to accomplish.  If you choose to use this option it can take months for the seeds to germinate.

If you are planting seed outside, we suggest seeding in late fall, and let the Milkweed seed lay on the ground through winter. Milkweed seed will have a long winter of dormancy, so once the sun comes out and the ground warms in the spring, the seeds will germinate on their own.

 

Transplanting Milkweed Seedling Outdoors

Step 3: Milkweed does well in open areas with full sunlight exposure areas like fields, parks, cultivated gardens, roadsides, highway medians, and road sides.  We suggest transplanting Milkweed when the plant is no larger than 3 inches tall. In most cases in transplanting, the Milkweed plant will go though some shock and could lose all its leaves. This happens, don’t panic. The plant is trying to establish its roots and will eventually grow leaves again.  This is the main reason we suggest planting seeds in peat pots, because Milkweed roots are very sensitive.  Peat Pots breakdown over time in the ground, which allows the milkweed roots to grows without being disrupted.  We found this to be the best way to transplant. If you decide to plant in plastic containers, but make sure it’s deep enough for roots to grow. If you receive a plant already grown in plastic, be careful to take out the plant and not disturb the roots.Transplanting a Milkweed

When to Plant Milkweed

Soil moisture and temperature are very important when growing Milkweed. The best time to plant Milkweed is in early spring after the danger of frost has passed.  If you plant seeds late in the spring, the seeds may not grow due toCommon Milkweed Field Grown germination time and temperature. Common Milkweed seed doesn’t germinate over 85 degrees.

Caring for Milkweed Plants

Once your seedling is planted, water it for a few days to get it established, but after that, the plant doesn’t need a lot of supplemental water. Only water if you have an unusual dry spell.  Peat pots are nice to use, but you need to be sure there is no top edge above the soil line after transplanting. In dry climates, this will wick away valuable soil moisture. A small 2 1/2" diameter x 3 in. deep pot is ideal. Asclepias are somewhat finicky native plants. So minimizing the time growing in a pot and transplanting them as young plants is the best approach.

Are you excited about saving the monarchs? Have any tips for growing milkweed seed? Share with us on facebook or instagram, we would love to see. Happy Growing!

22 thoughts on “How to Germinate and Grow Milkweed Seed”

  • Wanda Fleming

    Where can I get Milkweed,either seed or plants?

    Reply
    • Amanda

      Hi Wanda,

      We sell Milkweed seed here: http://www.americanmeadows.com/wildflower-seeds/milkweed-seeds
      and plants here: http://www.americanmeadows.com/butterfly-weed

      Happy Gardening,

      Amanda

      Reply
  • Pamela kanarr

    I received the milkweed seeds the packet states it has already been cold stratified. I was told that I needed to do this. I just wanted to be sure

    Reply
    • Amanda

      Hi Pamela,

      If you received the packet from us, we would recommend still going through the cold stratification process. Let us know if you have any other questions.

      Happy Gardening,

      Amanda

      Reply
  • Ray Dupont

    Please give me tips for getting stratification and growth with seeds in jugs that are placed outside in Indiana in February. Thanks.

    Reply
    • jprince

      Hi Ray,

      you can get good germination outside in a northern spot like Indiana, as long as you time things correctly. That's the tricky part! Ideally, the seeds would be subjected to cold enough temps to stratify naturally through the cycle of freezing and thawing, but after they sprout, you'll have to make sure that the tender baby plants are no longer subjected to freezing temperatures. One way to do this is to 'winter sow' the seeds; leave them outdoors in the jugs in the heart of winter and watch carefully as they sprout in spring. If you see cold weather coming, you'll need to bring them indoors for protection until things warm up. Otherwise, you can refrigerate the seeds and sow them in your jugs indoors, bringing them out as soon as the conditions are favorable. Good luck and keep us posted! - Jenny

      Reply
  • sue

    Are both milkweed varieties good for Monarchs? I have wild milkweed and I've had caterpillars but then no chrysalis appear. ?????

    Reply
    • Amanda

      Hi Sue,

      Thanks for the question. Yes, any variety of Milkweed will help attract butterflies to the garden.

      Happy Gardening,

      Amanda

      Reply
    • jprince

      Sue - remember too that caterpillars are easy prey! If you see them disappear quickly, they likely became food for wasps or ants. Many folks find a way to protect caterpillars by bringing them into a screened porch or pool cage area, or by creating temporary habitats with laundry hampers, screened fish tanks, and even buckets covered with stretched-out pantyhose. If you do this, you'll need to provide them with milkweed cuttings until they're ready to be released - which is the fun part! - Jenny

      Reply
    • Elaine Clark

      I had a lot of monarch caterpillars this year, most get eaten by birds, insects, dragonflies. So i started to being them in and put them in a reptile cage and now I am getting the chrysalis. make sure you get a reptile cage with a plastic screened top. there re so many predators out there jumping spiders praying mantas, your outdoor cats dispensary.I am using a little book called How to raise Monarch Butterflies , by Carol Pasternak and its very informative.
      Good luck <3
      Elaine

      Reply
  • Jos

    I have cold stratified common milkweed seeds. I want to establish them on a very steep slope that is already filled with native and non native plants and shrubs. Can I just hand broadcast the seeds or should they be planted under soil? Also what about ground temps?

    Reply
    • Jenny

      Hi Jos. You stratified your milkweed seeds! Excellent, you're halfway there. Most milkweed seeds need a warm soil to germinate - around 70 degrees F, and they do want to pushed into the earth at least an inch deep. This is why so many folks choose to sow their stratified seeds in flats and grow them to 4-6 inches in height before transplanting them outdoors. Not sure if this will work for your scenario, but it is another option for springtime planting. Fall planting can be done by scattering unstratified seeds over the area. Hope you see lots of Monarchs - Jenny

      Reply
  • Carolyn

    I have 15 asclepsis tuberosas transplanted in small pots. My problem is that very few of them are really green. Leaves are yellow. I have them in compost and have been careful not to overwater. I have lost 7 plants already. Do you have any suggestions. Thank you.

    Reply
    • Jenny

      Carolyn - ok, here are two suggestions for you to try and remedy those yellow leaves! 1) I'm not sure where you've got them set out, but there's a chance that they simply need more sunlight. If it's possible that they're too shaded, definitely try moving them into a sunnier spot. 2) Compost can be a tricky potting medium, because it's rarely tested for nutrients. If sunlight is not your issue, I would recommend transplanting your seedlings into a potting mix that lists the nutrients right on the bag. This way you'll know for sure that your asclepias is getting proper nutrition - they should green-up quickly. Hope this helps and Happy Gardening! - Jenny

      Reply
      • Carolyn

        I have had them in my hothouse, but thought maybe it was getting too warm (I'm in the CA foothills). So I moved them outside. I will try your suggestion and re-pot, though I have read that they're very sensitive to having their roots moved. Thanks again.

        Reply
        • Jenny

          I think you're right to be wary of disturbing their roots; however, young plants are a bit less susceptible - so you may just get away with it! Asclepias has a long tap root and if you try to dig it up and transplant it, you almost always meet failure. But if you take a small potted plant and put it into a larger pot, there's a good chance that the taproot will stay intact and unharmed. Keep us posted!

          Reply
  • Lindsey Shorter
    Lindsey Shorter August 6, 2016 at 1:06 pm

    I purchased some Swamp Milkweed seeds. The package doesn't mention that they are stratified. I live in Southern Illinois. Should I plant them this fall so they go through the stratification process outdoors over the winter? Thank you so much!

    Reply
    • Jenny

      Hi Lindsey, you could certainly plant them outside this fall to make sure that they go through the stratification process; be sure that you wait to scatter them until after a killing frost. Otherwise, we've had success with refrigerating our seeds in damp ziploc bags inside the refrigerator for a couple of months (you can tape them to the underside of a shelf to keep them out of your way) to get them stratified before planting in the spring. That should do the trick if you're unable to plant this fall! Happy Gardening - Jenny

      Reply
  • Janine

    I have plants that are planted in my garden. We have some harsh winter weather here in Pennsylvania and I was wondering what I need to do for these plants? Should I cut them back? And if so when and how short? I think 2 of the plants are Swamp Milkweed while the other 2 I'm not that familiar. But I do not want to lose any if I can help it. Thanks for your reply!

    Reply
    • Jenny

      Hi Janine, great question! Technically, your Swamp Milkweed is perennial in your zone and you shouldn't have a problem keeping it happy through the winter (mine have survived and thrived for several years in Northern Vermont). However, for some extra insurance, you could scatter some seeds from each plant all around your planting area after the first killing frost. That way, you'll have new plants emerging if these don't survive the winter. As far as the other varieties, you might look at our site to try and ID what you've got so that we can give you good advice for those as well: http://www.americanmeadows.com/wildflower-seeds/milkweed-seeds - Happy Gardening, Jenny

      Reply
  • delbert hayes

    it is septin iowa, I have 3 ft plants with pods on, do I pick the pods off and pull the little dark seed of the white silky fiber and put in a bag in refrig?

    Reply
    • Jenny

      Delbert - that is definitely an option, although you'll want to make sure that your seeds are stored in damp paper towels and I'm worried that you might have to check on them a few times before spring to make sure that they're moist. What has worked very well for me is to leave the plants as-is and harvest the seeds in late winter or early spring. I always find plenty still attached to the plant; however, if you're nervous about the wind blowing them away before you can harvest, you may remove a pod now (or within the next 2 months) and store it in a safe place outdoors. That way, your seeds will be stratified naturally and you won't have to worry about them disappearing. Hope this helps and Happy Gardening - Jenny

      Reply
Leave a Reply
You are using an out-of-date browser.

You will still be able to shop AmericanMeadows.com, but some functionality may not work unless you update to a modern browser. Update My Browser

×

Please wait...

Item added to your cart

has been added to your cart.