The Life Cycle of Milkweed

Monarchs LOVE Swamp Milkweed (<em>Aslcepias incarnata</em>) if you have rich soil and moderate to wet conditions, this is the one to grow! It's native to most of the continental US, except the West coast.

Monarchs LOVE Swamp Milkweed (Aslcepias incarnata) if you have rich soil and moderate to wet conditions, this is the one to grow!

You’ve read about the plight of the Monarch Butterfly and are ready to support this regal species by including Milkweed in your garden. But when is best to plant it? What does it look like? When will it flower?

We provide US native milkweed all over the country to people in urban centers, and deep in the countryside, of all ages and walks of life. In doing so, I have run into a great deal of misconceptions. A deeper understanding of the life cycle of the plant can help your milkweed patch become a booming hub of beautiful and unusual pollinators, including the Monarch Butterfly!


Milkweed Life Cycle

<em>Asclepias syriaca</em>, Common Milkweed, ready to disperse seeds. A perfect time to harvest the seeds.

Asclepias syriaca, Common Milkweed, ready to disperse seeds. A perfect time to harvest the seeds.

Dissemination and Germination

When milkweed goes to seed in the Fall, the seeds take aloft on their down, and finally land, working their way to the soil surface during the rains of the Fall. And there the seed will rest, and not germinate until Spring. Even if there is a warm spell. Why? To keep it safe during the Winter. If it germinates in the fall, and the seedling is very young, small and tender when the freezes do come, the tender roots will not survive.  How does it do this? There are enzymes in the papery seed coat that inhibit germination. That enzyme breaks down over the Winter, and the seed can grow at last, in the Spring when temperatures are sufficient. Germinating in the Spring, it has all Summer to establish roots.

Tip: when pods are approaching full size, but still green, tie a rubber band or string around them. They won’t open up and get everywhere!  Mark the plants and be certain to return. It’s no good to bind the seeds, and then not harvest them.  Harvest when the pods look mottled brown and no more milky sap is reaching the pods.  Leave at least half the pods for nature to sow in her own ways.

The mistakes commonly made:

  • Harvesting the seed too soon. The pod should be drying out and beginning to split. The seeds will have edges that appear like dry, dark brown colored paper. Seeds that are too young will appear orangish and translucent on the edges.
  • Planting in the Spring. Only a small percentage of milkweed seeds will break dormancy when planted in the Spring. Southern lines of milkweed and Butterflyweed (Aslcepias tuberosa) seem somewhat more cooperative. Fall is the best time to plant.
  • Planting INDOORS in the Fall. The seeds need to be outside. They are a WILD flower. They generally will not sprout indoors.
  • Planting in a container. Milkweed grows substantial roots in its first year. It will long suffer if grown in a container more than just a fraction of its first year. Get it outside in the Earth, where it belongs.


The First Year

A first year <em>Asclepias incarnata</em> plant (Swamp Milkweed) will have to wait another two years before it's blushing vivid pink with nectar-rich flowers.

A first year Asclepias incarnata plant (Swamp Milkweed) will have to wait another two years before it’s blushing vivid pink with nectar-rich flowers.

The first year the young milkweed builds its roots. Deep sturdy roots that will help it survive drought, floods, and freeing temps. It works so hard, at developing its roots, as a matter of fact, that the lovely tender green leaves that Monarch caterpillars love are quite diminutive, altogether unimpressive. I keep a close eye on first-year plants. Believe it or not, Monarchs can find them! And boy, do their caterpillars eat. A first year plant may not be sufficient to feed a caterpillar. Be braced to transfer the lovely boys and girls to a larger plant, or rear them on harvested milkweed under the safety of your watch.

Mistakes commonly made:

  • Not recognizing the small plant for what it really is- Milkweed! I have heard back from disappointed customers, that they didn’t see the iconic 4′ tall stems with softball-sized clumps of flowers. When I suggested that they look for more modest plants, they were able to spot their young milkweed growing healthfully among the grasses.
  • Not waiting long enough for germination. Wildflowers evolved any strategies for survival. One of these is a variable germination rate. Suppose there is a drought in the late spring. Early sprouters will perish. The later sprouting seeds will come up and thrive. Butterflyweed is notoriously stubborn, sometimes coming up as late as July!

The Second Year

Monarchs readily lay eggs on second year milkweed plants like this Common Milkweed (Asclepias syriaca).

Monarchs readily lay eggs on second year milkweed plants like this Common Milkweed (Asclepias syriaca).

Here we go! The plant is now able to produce a considerable amount of foliage. In the case of a thriving larger-leaved variety, maybe enough to feed a Monarch caterpillar! Adult Monarchs will readily find the plant. Scientists still aren’t certain how monarchs recognize milkweed from the air, but once they land on it, chemical sensors (kind of like tastebuds) on the feet of the Monarch recognize the milkweed at once!

Mistakes commonly made: 

  • The plant looks a lot like milkweed now. But it rarely will flower the second year. Being disappointed or thinking that you are doing something wrong is the only issue. Just be patient!


Showy Milkweed, <em>Asclepias speciosa</em> produces large stunning flowers its third year. It is native to the American Central Prairies and West.

Showy Milkweed, Asclepias speciosa produces large stunning flowers its third year. It is native to the American Central Prairies and West.

The Third Year

Flowers at last! The third year a mature milkweed plant has developed, it produces large lush foliage, ample flowers, and will serve as a nectar source for adult butterflies and bees, and there is plenty of leaves for the caterpillars. After a long-bloom that can last much of the summer, seed pods will form that open in the fall, starting the cycle anew. You can collect these seeds once the pods have begun to turn brown and open, sowing your own milkweed seeds.

Mistakes commonly made:

  • Harvesting seeds too early.
  • Using insecticide to kill aphids.

Ranges of our Native Milkweeds

It is important to plant milkweeds that are native to your area. This is for the welfare of the plant and the Monarch Butterflies, who may rely on the species of milkweeds they encounter to navigate on their journey. Below are range maps of the several species of US native milkweed for which we carry Seed balls.  There are many additional milkweeds that are also native. Some have restricted ranges, some are endangered or threatened. Most, unfortunately, are next to impossible to purchase seeds for. We have worked hard to find high quality milkweed seed for every part of the continental US. To see current data for ALL US native milkweed ranges, check the Biota of North America Program. They produced the maps, below.

Click maps to go see the image and description for the species or to purchase.

56 Comments

  1. Most helpful! Thank you. Chairman, Springdale for Monarchs

  2. DO MILKWEE SEEDS ONLY LAST SO LONG BEFORE YOU CAN PLANT THEM????

    • Milkweed seeds can keep a few years if kept cool and dry.

    • Milkweed has optimal germination after one year of storage. Most milkweeds need to endure a cold season before they will grow.

      • How poisonous is the plant? I have 4 tall ones (about 4.5 feet tall) that shot up this year and bloomed. I like them, but I am worried about my small children and German shepherd. Is this plant highly poisonous and what kind of contact would be required to experience negative effects? The children and pets won’t eat them, but may occasionally have skin contact with the plant if left there.

  3. Thank you so much for this informative artice. Greatly appreciated!

  4. Your maps have no key. Do I buy the recommended variety if I like in the dark green, light green, or yellow area? I assume the tan area is out of range.

    Otherwise, I have found this site to be very helpful.

  5. What is the lifespan of a milkweed plant?

  6. This is my second year growing from potted nursery plants. Do I cut back the canes or the surface or leave them to grow as they stand?

    Thanks.

  7. I’m in California and just ordered my milkweed seeds. are they already cold stratified? if I plant them and soak them well in my garden should they grow? or should I put them in the fridge for a few weeks? then plant

  8. Thank you for this article…it really helped solve some of the mysteries in my milkweed garden!

  9. I purchased Asclepias curassavica and live in del Mar CA. From nursery and they have little green buds in the leaves. About 10 inches tall with 3 different stems.
    1. Will it grow?
    2. Should I separated the stems?
    3. How old do you suspect it to be?

    • Asclepias curassavica is not a US native milkweed. It attracts monarchs so densely that it can spread the infectious OE disease that is killing Monarchs in the south. We never recommend this plant for Monarchs. Please consider replacing the tropical milkweed with native California species that are now available like Asclepias fascicularis and Asclepias eriocarpa.

  10. How long does swamp milkweed live?

  11. This is my second year in attempting to grow milkweed here in Northern California. This year some of my plants are at least 72″ tall. My question is do I need to water them to extend the growing season? Also last fall I was walking along tha Trinity River and found myself surrounded by Monarchs and low and behold I was also in an area covered with Milkweed. We spend our summers about three miles upriver and have never seen even one Monarch in the area. I hope that you can help with my watering question.

    • What does waiting moderation mean?

      • I water in moderation or waiting in moderation. To water in moderation is to keep moist but not wet. The soil should not appear shiny once the water is absorbed.

        Did you find a typo in our article? Let me know, I’ll fix it right away!

    • 7′ tall! Wow, do you know what species they are?

      We recommend letting nature determine the watering for native wildflowers. In areas with annual dry cycles, the plants native to that area are adapted with deeper roots, and periods of dormancy.

  12. Hi, I just ordered and received the Green Antelope Horn Milkweed and the Woolypod Milkweed seedballs. I live in Austin, TX and it is already starting to heat up. Can I plant now? Should I put the seedballs in the refrigerator first? If so, how long should I keep them there? Will they have flowers this year? I love my tropical milkweed and it was covered w/ blossoms and butterflies all last fall. It was spectacular! I am hoping to introduce some different types of milkweed and could use your advice. Thank you!

    • Hi Amy, We recommend planting these species only in the Fall to mid winter. The seed balls tend to mold if put in the fridge. You can certainly try, but both species are for fall planting. In Springtime in Texas, I recommend our Spring Planting Butterflyweed (Asclepias tuberosa) for Spring planting.

  13. We are on our second year if a couple of milkweed plants. Suprisingly they came back. I didn’t see flowering, but was pleased to see a few fat catepillers last year and hope to see more this year. What I did not see were pods. Was I supposed to see them on a first year plant? I really want to grow more from seed and the two plants I have are coming back in force.

    • Hi Andrea,
      Milkweed comes back year after year in good conditions. It is a perennial, so it should come back. Flowering doesn’t occur until the second or third year, and only after flowering will you get pods.

      Monarch caterpillars eat the leaves, so you can see them the first year.

      • My Asclepias Syriaca (common Milkweed)won’t bloom after 3 years? The plants are growing large and lush and multiplying beautifully, but will not bloom for some reason. I live in Atlanta, Ga.

        • I suspect that it may be receiving too much nitrogen, which encourages leaf growth, but often reduces blooms. If the plants were stressed, that could be a reason, but they seem to be doing well. If you are fertilizing, cut back on that. Nitrogen eventually will be lost from the soil and they will bloom. Monarchs don’t need the flowers to reproduce, so keep your eye out for caterpillars!

  14. I have been growing common milkweed indoors. They are about 3 inches already. Can I plant them in the summer in a shaded location? In New Jersey

    • It will prefer a sunny location. Break it in gradually to the outdoors. Introduce it to shade on mild days. Shelter from wind, and be certain it is well watered. Gradually increase the exposure that it receives for two weeks, then plant it in a sunny location, keeping moist for a month while the roots connect with the native soil.

  15. I planted 4 plants in April and in June the monarch caterpillars ate then down. There are hardly any leaves left.
    Will they come back this year. I am in central Florida.

    • Hi Jerry,
      Great news that you are feeding the Monarchs! Yes, the plants will come back next year. Co-evolution is beneficial to both species in this case. Congrats on helping this year’s generation of Monarchs!

  16. Ok so I’m a complete novice to milkweed. I ordered on a site and it said I could go ahead and plant. I must have a 1,000 different varieties of southeast milkweed planted. It’s been about two months and nothing. I do have a few seeds sprouting up but it could be any number of different southeast seeds for pollinators. I don’t see anything that looks like milkweed. My question is will they be okay and sprout next spring? Thank you

  17. I have a huge milkweed plant growing among my lily of the valley. I would like to transplant it to another location. When should I do this. I live in Minnesota

    • Milkweed does not transplant well. If you must, do it in late fall, after it has gone to seed and died back. Dig up as much of the root system as possible, and plant in well, draining soil in a sunny location. Common Milkweed rhizomes are long and horizontal. Plant about 4″ deep and tamp the soil down well.

  18. In what stage does the milkweed have to be for the monarch to lay her eggs

    • Monarchs lay eggs on the leaves of milkweed as they migrate North. Typically, they do this on second year and older plants, as they are taller and easier to find. Also have more leaves for the caterpillars, who eat a lot!

  19. I live in South Carolina (zone 7/8) what is the best time of the year to plant milk weed??

  20. Do I need to be concerned about deer eating milkweed? I have seeds to plant but deer frequent the area I planned to plant.

  21. I have second year plants in the Chicago area that are very tall and have pods. I haven’t seen any Monarchs yet. Is it too late for them to feed and lay eggs?
    Thanks

    • It is getting late in the season for reproduction, but not too late! The female monarch looks for the leaves, not the flowers, so you may still get some! Not very many monarchs here in central PA this year either. It was a rough winter in their roosting forest in Mexico. Numbers are down even more. 🙁

      • I just noticed this morning that there’s at least six monarch caterpillar’s on the milkweed!
        All but one are pretty big, two were eating the pods instead of the leaves. The pods are green and closed, I had no idea that they eat those too. I took some photo’s but can’t post them here.

  22. I live in the Cumberland foothills. We have been here 9 yrs. in the beginning, we had tons of milkweed that had big puffy blooms that lasted a good part of the summer. Now we have small blooms that die off in about a month. Do not see many Monarchs either.i have pics as well but cannot send them here

    • Several things can cause a perennial to die. Milkweed is notoriously hardy, but changes in climate can send it reeling. So can salts from roads, and also changes in hydrology. If a ditch drains differently or a new driveway sheds water in a different direction, plant roots can’t always adapt to the change.

      You might try collecting some seed pods this fall from local plants that are thriving. Plant some new ones among the older plants. Maybe they will grow to the current conditions and fare better.

  23. All of a sudden lots of monarch caterpillars. Very excited. Took five in to raise for my grandchildren to experience feeding them etc. lots of fun. Also saving them from the town grass cutter.

  24. I live in the foot hills of the Catskills in upstate New York

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