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.

15 Comments

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

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

  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. 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.

  6. 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

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